SYSTEMD.EXEC(5) systemd.exec SYSTEMD.EXEC(5)
systemd.exec - Execution environment configuration
service.service, socket.socket, mount.mount, swap.swap
Unit configuration files for services, sockets, mount points, and
swap devices share a subset of configuration options which define the
execution environment of spawned processes.
This man page lists the configuration options shared by these four
unit types. See systemd.unit(5) for the common options of all unit
configuration files, and systemd.service(5), systemd.socket(5),
systemd.swap(5), and systemd.mount(5) for more information on the
specific unit configuration files. The execution specific
configuration options are configured in the [Service], [Socket],
[Mount], or [Swap] sections, depending on the unit type.
In addition, options which control resources through Linux Control
Groups (cgroups) are listed in systemd.resource-control(5). Those
options complement options listed here.
A few execution parameters result in additional, automatic
dependencies to be added:
· Units with WorkingDirectory=, RootDirectory=, RootImage=,
RuntimeDirectory=, StateDirectory=, CacheDirectory=,
LogsDirectory= or ConfigurationDirectory= set automatically gain
dependencies of type Requires= and After= on all mount units
required to access the specified paths. This is equivalent to
having them listed explicitly in RequiresMountsFor=.
· Similar, units with PrivateTmp= enabled automatically get mount
unit dependencies for all mounts required to access /tmp and
/var/tmp. They will also gain an automatic After= dependency on
systemd-tmpfiles-setup.service(8).
· Units whose standard output or error output is connected to
journal or kmsg (or their combinations with console output, see
below) automatically acquire dependencies of type After= on
systemd-journald.socket.
· Units using LogNamespace= will automatically gain ordering and
requirement dependencies on the two socket units associated with
systemd-journald@.service instances.
The following settings may be used to change a service's view of the
filesystem. Please note that the paths must be absolute and must not
contain a ".." path component.
WorkingDirectory=
Takes a directory path relative to the service's root directory
specified by RootDirectory=, or the special value "~". Sets the
working directory for executed processes. If set to "~", the home
directory of the user specified in User= is used. If not set,
defaults to the root directory when systemd is running as a
system instance and the respective user's home directory if run
as user. If the setting is prefixed with the "-" character, a
missing working directory is not considered fatal. If
RootDirectory=/RootImage= is not set, then WorkingDirectory= is
relative to the root of the system running the service manager.
Note that setting this parameter might result in additional
dependencies to be added to the unit (see above).
RootDirectory=
Takes a directory path relative to the host's root directory
(i.e. the root of the system running the service manager). Sets
the root directory for executed processes, with the chroot(2)
system call. If this is used, it must be ensured that the process
binary and all its auxiliary files are available in the chroot()
jail. Note that setting this parameter might result in additional
dependencies to be added to the unit (see above).
The MountAPIVFS= and PrivateUsers= settings are particularly
useful in conjunction with RootDirectory=. For details, see
below.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RootImage=
Takes a path to a block device node or regular file as argument.
This call is similar to RootDirectory= however mounts a file
system hierarchy from a block device node or loopback file
instead of a directory. The device node or file system image file
needs to contain a file system without a partition table, or a
file system within an MBR/MS-DOS or GPT partition table with only
a single Linux-compatible partition, or a set of file systems
within a GPT partition table that follows the Discoverable
Partitions Specification[1].
When DevicePolicy= is set to "closed" or "strict", or set to
"auto" and DeviceAllow= is set, then this setting adds
/dev/loop-control with rw mode, "block-loop" and "block-blkext"
with rwm mode to DeviceAllow=. See systemd.resource-control(5)
for the details about DevicePolicy= or DeviceAllow=. Also, see
PrivateDevices= below, as it may change the setting of
DevicePolicy=.
Units making use of RootImage= automatically gain an After=
dependency on systemd-udevd.service.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RootImageOptions=
Takes a comma-separated list of mount options that will be used
on disk images specified by RootImage=. Optionally a partition
number can be prefixed, followed by colon, in case the image has
multiple partitions, otherwise partition number 0 is implied.
Options for multiple partitions can be specified in a single line
with space separators. Assigning an empty string removes previous
assignments. For a list of valid mount options, please refer to
mount(8).
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RootHash=
Takes a data integrity (dm-verity) root hash specified in
hexadecimal, or the path to a file containing a root hash in
ASCII hexadecimal format. This option enables data integrity
checks using dm-verity, if the used image contains the
appropriate integrity data (see above) or if RootVerity= is used.
The specified hash must match the root hash of integrity data,
and is usually at least 256 bits (and hence 64 formatted
hexadecimal characters) long (in case of SHA256 for example). If
this option is not specified, but the image file carries the
"user.verity.roothash" extended file attribute (see xattr(7)),
then the root hash is read from it, also as formatted hexadecimal
characters. If the extended file attribute is not found (or is
not supported by the underlying file system), but a file with the
.roothash suffix is found next to the image file, bearing
otherwise the same name (except if the image has the .raw suffix,
in which case the root hash file must not have it in its name),
the root hash is read from it and automatically used, also as
formatted hexadecimal characters.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RootHashSignature=
Takes a PKCS7 formatted binary signature of the RootHash= option
as a path to a DER encoded signature file or as an ASCII base64
string encoding of the DER encoded signature, prefixed by
"base64:". The dm-verity volume will only be opened if the
signature of the root hash signature is valid and created by a
public key present in the kernel keyring. If this option is not
specified, but a file with the .roothash.p7s suffix is found next
to the image file, bearing otherwise the same name (except if the
image has the .raw suffix, in which case the signature file must
not have it in its name), the signature is read from it and
automatically used.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RootVerity=
Takes the path to a data integrity (dm-verity) file. This option
enables data integrity checks using dm-verity, if RootImage= is
used and a root-hash is passed and if the used image itself does
not contains the integrity data. The integrity data must be
matched by the root hash. If this option is not specified, but a
file with the .verity suffix is found next to the image file,
bearing otherwise the same name (except if the image has the .raw
suffix, in which case the verity data file must not have it in
its name), the verity data is read from it and automatically
used.
This option is supported only for disk images that contain a
single file system, without an enveloping partition table. Images
that contain a GPT partition table should instead include both
root file system and matching Verity data in the same image,
implementing the Discoverable Partition Specification[1].
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
MountAPIVFS=
Takes a boolean argument. If on, a private mount namespace for
the unit's processes is created and the API file systems /proc,
/sys, and /dev are mounted inside of it, unless they are already
mounted. Note that this option has no effect unless used in
conjunction with RootDirectory=/RootImage= as these three mounts
are generally mounted in the host anyway, and unless the root
directory is changed, the private mount namespace will be a 1:1
copy of the host's, and include these three mounts. Note that the
/dev file system of the host is bind mounted if this option is
used without PrivateDevices=. To run the service with a private,
minimal version of /dev/, combine this option with
PrivateDevices=.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
BindPaths=, BindReadOnlyPaths=
Configures unit-specific bind mounts. A bind mount makes a
particular file or directory available at an additional place in
the unit's view of the file system. Any bind mounts created with
this option are specific to the unit, and are not visible in the
host's mount table. This option expects a whitespace separated
list of bind mount definitions. Each definition consists of a
colon-separated triple of source path, destination path and
option string, where the latter two are optional. If only a
source path is specified the source and destination is taken to
be the same. The option string may be either "rbind" or "norbind"
for configuring a recursive or non-recursive bind mount. If the
destination path is omitted, the option string must be omitted
too. Each bind mount definition may be prefixed with "-", in
which case it will be ignored when its source path does not
exist.
BindPaths= creates regular writable bind mounts (unless the
source file system mount is already marked read-only), while
BindReadOnlyPaths= creates read-only bind mounts. These settings
may be used more than once, each usage appends to the unit's list
of bind mounts. If the empty string is assigned to either of
these two options the entire list of bind mounts defined prior to
this is reset. Note that in this case both read-only and regular
bind mounts are reset, regardless which of the two settings is
used.
This option is particularly useful when RootDirectory=/RootImage=
is used. In this case the source path refers to a path on the
host file system, while the destination path refers to a path
below the root directory of the unit.
Note that the destination directory must exist or systemd must be
able to create it. Thus, it is not possible to use those options
for mount points nested underneath paths specified in
InaccessiblePaths=, or under /home/ and other protected
directories if ProtectHome=yes is specified.
TemporaryFileSystem= with ":ro" or ProtectHome=tmpfs should be
used instead.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
MountImages=
This setting is similar to RootImage= in that it mounts a file
system hierarchy from a block device node or loopback file, but
the destination directory can be specified as well as mount
options. This option expects a whitespace separated list of mount
definitions. Each definition consists of a colon-separated tuple
of source path and destination directory. Each mount definition
may be prefixed with "-", in which case it will be ignored when
its source path does not exist. The source argument is a path to
a block device node or regular file. If source or destination
contain a ":", it needs to be escaped as "\:". The device node or
file system image file needs to follow the same rules as
specified for RootImage=. Any mounts created with this option are
specific to the unit, and are not visible in the host's mount
table.
These settings may be used more than once, each usage appends to
the unit's list of mount paths. If the empty string is assigned,
the entire list of mount paths defined prior to this is reset.
Note that the destination directory must exist or systemd must be
able to create it. Thus, it is not possible to use those options
for mount points nested underneath paths specified in
InaccessiblePaths=, or under /home/ and other protected
directories if ProtectHome=yes is specified.
When DevicePolicy= is set to "closed" or "strict", or set to
"auto" and DeviceAllow= is set, then this setting adds
/dev/loop-control with rw mode, "block-loop" and "block-blkext"
with rwm mode to DeviceAllow=. See systemd.resource-control(5)
for the details about DevicePolicy= or DeviceAllow=. Also, see
PrivateDevices= below, as it may change the setting of
DevicePolicy=.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
These options are only available for system services and are not
supported for services running in per-user instances of the service
manager.
User=, Group=
Set the UNIX user or group that the processes are executed as,
respectively. Takes a single user or group name, or a numeric ID
as argument. For system services (services run by the system
service manager, i.e. managed by PID 1) and for user services of
the root user (services managed by root's instance of systemd
--user), the default is "root", but User= may be used to specify
a different user. For user services of any other user, switching
user identity is not permitted, hence the only valid setting is
the same user the user's service manager is running as. If no
group is set, the default group of the user is used. This setting
does not affect commands whose command line is prefixed with "+".
Note that this enforces only weak restrictions on the user/group
name syntax, but will generate warnings in many cases where
user/group names do not adhere to the following rules: the
specified name should consist only of the characters a-z, A-Z,
0-9, "_" and "-", except for the first character which must be
one of a-z, A-Z and "_" (i.e. digits and "-" are not permitted as
first character). The user/group name must have at least one
character, and at most 31. These restrictions are made in order
to avoid ambiguities and to ensure user/group names and unit
files remain portable among Linux systems. For further details on
the names accepted and the names warned about see User/Group Name
Syntax[2].
When used in conjunction with DynamicUser= the user/group name
specified is dynamically allocated at the time the service is
started, and released at the time the service is stopped — unless
it is already allocated statically (see below). If DynamicUser=
is not used the specified user and group must have been created
statically in the user database no later than the moment the
service is started, for example using the sysusers.d(5) facility,
which is applied at boot or package install time. If the user
does not exist by then program invocation will fail.
If the User= setting is used the supplementary group list is
initialized from the specified user's default group list, as
defined in the system's user and group database. Additional
groups may be configured through the SupplementaryGroups= setting
(see below).
DynamicUser=
Takes a boolean parameter. If set, a UNIX user and group pair is
allocated dynamically when the unit is started, and released as
soon as it is stopped. The user and group will not be added to
/etc/passwd or /etc/group, but are managed transiently during
runtime. The nss-systemd(8) glibc NSS module provides integration
of these dynamic users/groups into the system's user and group
databases. The user and group name to use may be configured via
User= and Group= (see above). If these options are not used and
dynamic user/group allocation is enabled for a unit, the name of
the dynamic user/group is implicitly derived from the unit name.
If the unit name without the type suffix qualifies as valid user
name it is used directly, otherwise a name incorporating a hash
of it is used. If a statically allocated user or group of the
configured name already exists, it is used and no dynamic
user/group is allocated. Note that if User= is specified and the
static group with the name exists, then it is required that the
static user with the name already exists. Similarly, if Group= is
specified and the static user with the name exists, then it is
required that the static group with the name already exists.
Dynamic users/groups are allocated from the UID/GID range
61184...65519. It is recommended to avoid this range for regular
system or login users. At any point in time each UID/GID from
this range is only assigned to zero or one dynamically allocated
users/groups in use. However, UID/GIDs are recycled after a unit
is terminated. Care should be taken that any processes running as
part of a unit for which dynamic users/groups are enabled do not
leave files or directories owned by these users/groups around, as
a different unit might get the same UID/GID assigned later on,
and thus gain access to these files or directories. If
DynamicUser= is enabled, RemoveIPC= and PrivateTmp= are implied
(and cannot be turned off). This ensures that the lifetime of IPC
objects and temporary files created by the executed processes is
bound to the runtime of the service, and hence the lifetime of
the dynamic user/group. Since /tmp/ and /var/tmp/ are usually the
only world-writable directories on a system this ensures that a
unit making use of dynamic user/group allocation cannot leave
files around after unit termination. Furthermore NoNewPrivileges=
and RestrictSUIDSGID= are implicitly enabled (and cannot be
disabled), to ensure that processes invoked cannot take benefit
or create SUID/SGID files or directories. Moreover
ProtectSystem=strict and ProtectHome=read-only are implied, thus
prohibiting the service to write to arbitrary file system
locations. In order to allow the service to write to certain
directories, they have to be allow-listed using ReadWritePaths=,
but care must be taken so that UID/GID recycling doesn't create
security issues involving files created by the service. Use
RuntimeDirectory= (see below) in order to assign a writable
runtime directory to a service, owned by the dynamic user/group
and removed automatically when the unit is terminated. Use
StateDirectory=, CacheDirectory= and LogsDirectory= in order to
assign a set of writable directories for specific purposes to the
service in a way that they are protected from vulnerabilities due
to UID reuse (see below). If this option is enabled, care should
be taken that the unit's processes do not get access to
directories outside of these explicitly configured and managed
ones. Specifically, do not use BindPaths= and be careful with
AF_UNIX file descriptor passing for directory file descriptors,
as this would permit processes to create files or directories
owned by the dynamic user/group that are not subject to the
lifecycle and access guarantees of the service. Defaults to off.
SupplementaryGroups=
Sets the supplementary Unix groups the processes are executed as.
This takes a space-separated list of group names or IDs. This
option may be specified more than once, in which case all listed
groups are set as supplementary groups. When the empty string is
assigned, the list of supplementary groups is reset, and all
assignments prior to this one will have no effect. In any way,
this option does not override, but extends the list of
supplementary groups configured in the system group database for
the user. This does not affect commands prefixed with "+".
PAMName=
Sets the PAM service name to set up a session as. If set, the
executed process will be registered as a PAM session under the
specified service name. This is only useful in conjunction with
the User= setting, and is otherwise ignored. If not set, no PAM
session will be opened for the executed processes. See pam(8) for
details.
Note that for each unit making use of this option a PAM session
handler process will be maintained as part of the unit and stays
around as long as the unit is active, to ensure that appropriate
actions can be taken when the unit and hence the PAM session
terminates. This process is named "(sd-pam)" and is an immediate
child process of the unit's main process.
Note that when this option is used for a unit it is very likely
(depending on PAM configuration) that the main unit process will
be migrated to its own session scope unit when it is activated.
This process will hence be associated with two units: the unit it
was originally started from (and for which PAMName= was
configured), and the session scope unit. Any child processes of
that process will however be associated with the session scope
unit only. This has implications when used in combination with
NotifyAccess=all, as these child processes will not be able to
affect changes in the original unit through notification
messages. These messages will be considered belonging to the
session scope unit and not the original unit. It is hence not
recommended to use PAMName= in combination with NotifyAccess=all.
These options are only available for system services and are not
supported for services running in per-user instances of the service
manager.
CapabilityBoundingSet=
Controls which capabilities to include in the capability bounding
set for the executed process. See capabilities(7) for details.
Takes a whitespace-separated list of capability names, e.g.
CAP_SYS_ADMIN, CAP_DAC_OVERRIDE, CAP_SYS_PTRACE. Capabilities
listed will be included in the bounding set, all others are
removed. If the list of capabilities is prefixed with "~", all
but the listed capabilities will be included, the effect of the
assignment inverted. Note that this option also affects the
respective capabilities in the effective, permitted and
inheritable capability sets. If this option is not used, the
capability bounding set is not modified on process execution,
hence no limits on the capabilities of the process are enforced.
This option may appear more than once, in which case the bounding
sets are merged by OR, or by AND if the lines are prefixed with
"~" (see below). If the empty string is assigned to this option,
the bounding set is reset to the empty capability set, and all
prior settings have no effect. If set to "~" (without any further
argument), the bounding set is reset to the full set of available
capabilities, also undoing any previous settings. This does not
affect commands prefixed with "+".
Example: if a unit has the following,
CapabilityBoundingSet=CAP_A CAP_B
CapabilityBoundingSet=CAP_B CAP_C
then CAP_A, CAP_B, and CAP_C are set. If the second line is
prefixed with "~", e.g.,
CapabilityBoundingSet=CAP_A CAP_B
CapabilityBoundingSet=~CAP_B CAP_C
then, only CAP_A is set.
AmbientCapabilities=
Controls which capabilities to include in the ambient capability
set for the executed process. Takes a whitespace-separated list
of capability names, e.g. CAP_SYS_ADMIN, CAP_DAC_OVERRIDE,
CAP_SYS_PTRACE. This option may appear more than once in which
case the ambient capability sets are merged (see the above
examples in CapabilityBoundingSet=). If the list of capabilities
is prefixed with "~", all but the listed capabilities will be
included, the effect of the assignment inverted. If the empty
string is assigned to this option, the ambient capability set is
reset to the empty capability set, and all prior settings have no
effect. If set to "~" (without any further argument), the ambient
capability set is reset to the full set of available
capabilities, also undoing any previous settings. Note that
adding capabilities to ambient capability set adds them to the
process's inherited capability set.
Ambient capability sets are useful if you want to execute a
process as a non-privileged user but still want to give it some
capabilities. Note that in this case option keep-caps is
automatically added to SecureBits= to retain the capabilities
over the user change. AmbientCapabilities= does not affect
commands prefixed with "+".
NoNewPrivileges=
Takes a boolean argument. If true, ensures that the service
process and all its children can never gain new privileges
through execve() (e.g. via setuid or setgid bits, or filesystem
capabilities). This is the simplest and most effective way to
ensure that a process and its children can never elevate
privileges again. Defaults to false, but certain settings
override this and ignore the value of this setting. This is the
case when SystemCallFilter=, SystemCallArchitectures=,
RestrictAddressFamilies=, RestrictNamespaces=, PrivateDevices=,
ProtectKernelTunables=, ProtectKernelModules=,
ProtectKernelLogs=, ProtectClock=, MemoryDenyWriteExecute=,
RestrictRealtime=, RestrictSUIDSGID=, DynamicUser= or
LockPersonality= are specified. Note that even if this setting is
overridden by them, systemctl show shows the original value of
this setting. Also see No New Privileges Flag[3].
SecureBits=
Controls the secure bits set for the executed process. Takes a
space-separated combination of options from the following list:
keep-caps, keep-caps-locked, no-setuid-fixup,
no-setuid-fixup-locked, noroot, and noroot-locked. This option
may appear more than once, in which case the secure bits are
ORed. If the empty string is assigned to this option, the bits
are reset to 0. This does not affect commands prefixed with "+".
See capabilities(7) for details.
These options are only available for system services and are not
supported for services running in per-user instances of the service
manager.
SELinuxContext=
Set the SELinux security context of the executed process. If set,
this will override the automated domain transition. However, the
policy still needs to authorize the transition. This directive is
ignored if SELinux is disabled. If prefixed by "-", all errors
will be ignored. This does not affect commands prefixed with "+".
See setexeccon(3) for details.
AppArmorProfile=
Takes a profile name as argument. The process executed by the
unit will switch to this profile when started. Profiles must
already be loaded in the kernel, or the unit will fail. If
prefixed by "-", all errors will be ignored. This setting has no
effect if AppArmor is not enabled. This setting not affect
commands prefixed with "+".
SmackProcessLabel=
Takes a SMACK64 security label as argument. The process executed
by the unit will be started under this label and SMACK will
decide whether the process is allowed to run or not, based on it.
The process will continue to run under the label specified here
unless the executable has its own SMACK64EXEC label, in which
case the process will transition to run under that label. When
not specified, the label that systemd is running under is used.
This directive is ignored if SMACK is disabled.
The value may be prefixed by "-", in which case all errors will
be ignored. An empty value may be specified to unset previous
assignments. This does not affect commands prefixed with "+".
LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=,
LimitRSS=, LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=,
LimitLOCKS=, LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=,
LimitRTPRIO=, LimitRTTIME=
Set soft and hard limits on various resources for executed
processes. See setrlimit(2) for details on the resource limit
concept. Resource limits may be specified in two formats: either
as single value to set a specific soft and hard limit to the same
value, or as colon-separated pair soft:hard to set both limits
individually (e.g. "LimitAS=4G:16G"). Use the string infinity to
configure no limit on a specific resource. The multiplicative
suffixes K, M, G, T, P and E (to the base 1024) may be used for
resource limits measured in bytes (e.g. "LimitAS=16G"). For the
limits referring to time values, the usual time units ms, s, min,
h and so on may be used (see systemd.time(7) for details). Note
that if no time unit is specified for LimitCPU= the default unit
of seconds is implied, while for LimitRTTIME= the default unit of
microseconds is implied. Also, note that the effective
granularity of the limits might influence their enforcement. For
example, time limits specified for LimitCPU= will be rounded up
implicitly to multiples of 1s. For LimitNICE= the value may be
specified in two syntaxes: if prefixed with "+" or "-", the value
is understood as regular Linux nice value in the range -20..19.
If not prefixed like this the value is understood as raw resource
limit parameter in the range 0..40 (with 0 being equivalent to
1).
Note that most process resource limits configured with these
options are per-process, and processes may fork in order to
acquire a new set of resources that are accounted independently
of the original process, and may thus escape limits set. Also
note that LimitRSS= is not implemented on Linux, and setting it
has no effect. Often it is advisable to prefer the resource
controls listed in systemd.resource-control(5) over these
per-process limits, as they apply to services as a whole, may be
altered dynamically at runtime, and are generally more
expressive. For example, MemoryMax= is a more powerful (and
working) replacement for LimitRSS=.
Resource limits not configured explicitly for a unit default to
the value configured in the various DefaultLimitCPU=,
DefaultLimitFSIZE=, ... options available in
systemd-system.conf(5), and – if not configured there – the
kernel or per-user defaults, as defined by the OS (the latter
only for user services, see below).
For system units these resource limits may be chosen freely. When
these settings are configured in a user service (i.e. a service
run by the per-user instance of the service manager) they cannot
be used to raise the limits above those set for the user manager
itself when it was first invoked, as the user's service manager
generally lacks the privileges to do so. In user context these
configuration options are hence only useful to lower the limits
passed in or to raise the soft limit to the maximum of the hard
limit as configured for the user. To raise the user's limits
further, the available configuration mechanisms differ between
operating systems, but typically require privileges. In most
cases it is possible to configure higher per-user resource limits
via PAM or by setting limits on the system service encapsulating
the user's service manager, i.e. the user's instance of
user@.service. After making such changes, make sure to restart
the user's service manager.
Table 1. Resource limit directives, their equivalent ulimit shell
commands and the unit used
┌─────────────────┬───────────────────┬─────────────────────┐
│Directive │ ulimit equivalent │ Unit │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitCPU= │ ulimit -t │ Seconds │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitFSIZE= │ ulimit -f │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitDATA= │ ulimit -d │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitSTACK= │ ulimit -s │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitCORE= │ ulimit -c │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitRSS= │ ulimit -m │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitNOFILE= │ ulimit -n │ Number of File │
│ │ │ Descriptors │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitAS= │ ulimit -v │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitNPROC= │ ulimit -u │ Number of Processes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitMEMLOCK= │ ulimit -l │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitLOCKS= │ ulimit -x │ Number of Locks │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitSIGPENDING= │ ulimit -i │ Number of Queued │
│ │ │ Signals │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitMSGQUEUE= │ ulimit -q │ Bytes │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitNICE= │ ulimit -e │ Nice Level │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitRTPRIO= │ ulimit -r │ Realtime Priority │
├─────────────────┼───────────────────┼─────────────────────┤
│LimitRTTIME= │ No equivalent │ Microseconds │
└─────────────────┴───────────────────┴─────────────────────┘
UMask=
Controls the file mode creation mask. Takes an access mode in
octal notation. See umask(2) for details. Defaults to 0022 for
system units. For units of the user service manager the default
value is inherited from the user instance (whose default is
inherited from the system service manager, and thus also is
0022). Hence changing the default value of a user instance,
either via UMask= or via a PAM module, will affect the user
instance itself and all user units started by the user instance
unless a user unit has specified its own UMask=.
CoredumpFilter=
Controls which types of memory mappings will be saved if the
process dumps core (using the /proc/pid/coredump_filter file).
Takes a whitespace-separated combination of mapping type names or
numbers (with the default base 16). Mapping type names are
private-anonymous, shared-anonymous, private-file-backed,
shared-file-backed, elf-headers, private-huge, shared-huge,
private-dax, shared-dax, and the special values all (all types)
and default (the kernel default of "private-anonymous
shared-anonymous elf-headers private-huge"). See core(5) for the
meaning of the mapping types. When specified multiple times, all
specified masks are ORed. When not set, or if the empty value is
assigned, the inherited value is not changed.
Example 1. Add DAX pages to the dump filter
CoredumpFilter=default private-dax shared-dax
KeyringMode=
Controls how the kernel session keyring is set up for the service
(see session-keyring(7) for details on the session keyring).
Takes one of inherit, private, shared. If set to inherit no
special keyring setup is done, and the kernel's default behaviour
is applied. If private is used a new session keyring is allocated
when a service process is invoked, and it is not linked up with
any user keyring. This is the recommended setting for system
services, as this ensures that multiple services running under
the same system user ID (in particular the root user) do not
share their key material among each other. If shared is used a
new session keyring is allocated as for private, but the user
keyring of the user configured with User= is linked into it, so
that keys assigned to the user may be requested by the unit's
processes. In this modes multiple units running processes under
the same user ID may share key material. Unless inherit is
selected the unique invocation ID for the unit (see below) is
added as a protected key by the name "invocation_id" to the newly
created session keyring. Defaults to private for services of the
system service manager and to inherit for non-service units and
for services of the user service manager.
OOMScoreAdjust=
Sets the adjustment value for the Linux kernel's Out-Of-Memory
(OOM) killer score for executed processes. Takes an integer
between -1000 (to disable OOM killing of processes of this unit)
and 1000 (to make killing of processes of this unit under memory
pressure very likely). See proc.txt[4] for details. If not
specified defaults to the OOM score adjustment level of the
service manager itself, which is normally at 0.
Use the OOMPolicy= setting of service units to configure how the
service manager shall react to the kernel OOM killer terminating
a process of the service. See systemd.service(5) for details.
TimerSlackNSec=
Sets the timer slack in nanoseconds for the executed processes.
The timer slack controls the accuracy of wake-ups triggered by
timers. See prctl(2) for more information. Note that in contrast
to most other time span definitions this parameter takes an
integer value in nano-seconds if no unit is specified. The usual
time units are understood too.
Personality=
Controls which kernel architecture uname(2) shall report, when
invoked by unit processes. Takes one of the architecture
identifiers x86, x86-64, ppc, ppc-le, ppc64, ppc64-le, s390 or
s390x. Which personality architectures are supported depends on
the system architecture. Usually the 64bit versions of the
various system architectures support their immediate 32bit
personality architecture counterpart, but no others. For example,
x86-64 systems support the x86-64 and x86 personalities but no
others. The personality feature is useful when running 32-bit
services on a 64-bit host system. If not specified, the
personality is left unmodified and thus reflects the personality
of the host system's kernel.
IgnoreSIGPIPE=
Takes a boolean argument. If true, causes SIGPIPE to be ignored
in the executed process. Defaults to true because SIGPIPE
generally is useful only in shell pipelines.
Nice=
Sets the default nice level (scheduling priority) for executed
processes. Takes an integer between -20 (highest priority) and 19
(lowest priority). See setpriority(2) for details.
CPUSchedulingPolicy=
Sets the CPU scheduling policy for executed processes. Takes one
of other, batch, idle, fifo or rr. See sched_setscheduler(2) for
details.
CPUSchedulingPriority=
Sets the CPU scheduling priority for executed processes. The
available priority range depends on the selected CPU scheduling
policy (see above). For real-time scheduling policies an integer
between 1 (lowest priority) and 99 (highest priority) can be
used. See sched_setscheduler(2) for details.
CPUSchedulingResetOnFork=
Takes a boolean argument. If true, elevated CPU scheduling
priorities and policies will be reset when the executed processes
fork, and can hence not leak into child processes. See
sched_setscheduler(2) for details. Defaults to false.
CPUAffinity=
Controls the CPU affinity of the executed processes. Takes a list
of CPU indices or ranges separated by either whitespace or
commas. Alternatively, takes a special "numa" value in which case
systemd automatically derives allowed CPU range based on the
value of NUMAMask= option. CPU ranges are specified by the lower
and upper CPU indices separated by a dash. This option may be
specified more than once, in which case the specified CPU
affinity masks are merged. If the empty string is assigned, the
mask is reset, all assignments prior to this will have no effect.
See sched_setaffinity(2) for details.
NUMAPolicy=
Controls the NUMA memory policy of the executed processes. Takes
a policy type, one of: default, preferred, bind, interleave and
local. A list of NUMA nodes that should be associated with the
policy must be specified in NUMAMask=. For more details on each
policy please see, set_mempolicy(2). For overall overview of NUMA
support in Linux see, numa(7).
NUMAMask=
Controls the NUMA node list which will be applied alongside with
selected NUMA policy. Takes a list of NUMA nodes and has the same
syntax as a list of CPUs for CPUAffinity= option. Note that the
list of NUMA nodes is not required for default and local policies
and for preferred policy we expect a single NUMA node.
IOSchedulingClass=
Sets the I/O scheduling class for executed processes. Takes an
integer between 0 and 3 or one of the strings none, realtime,
best-effort or idle. If the empty string is assigned to this
option, all prior assignments to both IOSchedulingClass= and
IOSchedulingPriority= have no effect. See ioprio_set(2) for
details.
IOSchedulingPriority=
Sets the I/O scheduling priority for executed processes. Takes an
integer between 0 (highest priority) and 7 (lowest priority). The
available priorities depend on the selected I/O scheduling class
(see above). If the empty string is assigned to this option, all
prior assignments to both IOSchedulingClass= and
IOSchedulingPriority= have no effect. See ioprio_set(2) for
details.
The following sandboxing options are an effective way to limit the
exposure of the system towards the unit's processes. It is
recommended to turn on as many of these options for each unit as is
possible without negatively affecting the process' ability to
operate. Note that many of these sandboxing features are gracefully
turned off on systems where the underlying security mechanism is not
available. For example, ProtectSystem= has no effect if the kernel is
built without file system namespacing or if the service manager runs
in a container manager that makes file system namespacing unavailable
to its payload. Similar, RestrictRealtime= has no effect on systems
that lack support for SECCOMP system call filtering, or in containers
where support for this is turned off.
Also note that some sandboxing functionality is generally not
available in user services (i.e. services run by the per-user service
manager). Specifically, the various settings requiring file system
namespacing support (such as ProtectSystem=) are not available, as
the underlying kernel functionality is only accessible to privileged
processes. However, most namespacing settings, that will not work on
their own in user services, will work when used in conjunction with
PrivateUsers=true.
ProtectSystem=
Takes a boolean argument or the special values "full" or
"strict". If true, mounts the /usr and the boot loader
directories (/boot and /efi) read-only for processes invoked by
this unit. If set to "full", the /etc directory is mounted
read-only, too. If set to "strict" the entire file system
hierarchy is mounted read-only, except for the API file system
subtrees /dev, /proc and /sys (protect these directories using
PrivateDevices=, ProtectKernelTunables=, ProtectControlGroups=).
This setting ensures that any modification of the vendor-supplied
operating system (and optionally its configuration, and local
mounts) is prohibited for the service. It is recommended to
enable this setting for all long-running services, unless they
are involved with system updates or need to modify the operating
system in other ways. If this option is used, ReadWritePaths= may
be used to exclude specific directories from being made
read-only. This setting is implied if DynamicUser= is set. This
setting cannot ensure protection in all cases. In general it has
the same limitations as ReadOnlyPaths=, see below. Defaults to
off.
ProtectHome=
Takes a boolean argument or the special values "read-only" or
"tmpfs". If true, the directories /home, /root, and /run/user are
made inaccessible and empty for processes invoked by this unit.
If set to "read-only", the three directories are made read-only
instead. If set to "tmpfs", temporary file systems are mounted on
the three directories in read-only mode. The value "tmpfs" is
useful to hide home directories not relevant to the processes
invoked by the unit, while still allowing necessary directories
to be made visible when listed in BindPaths= or
BindReadOnlyPaths=.
Setting this to "yes" is mostly equivalent to set the three
directories in InaccessiblePaths=. Similarly, "read-only" is
mostly equivalent to ReadOnlyPaths=, and "tmpfs" is mostly
equivalent to TemporaryFileSystem= with ":ro".
It is recommended to enable this setting for all long-running
services (in particular network-facing ones), to ensure they
cannot get access to private user data, unless the services
actually require access to the user's private data. This setting
is implied if DynamicUser= is set. This setting cannot ensure
protection in all cases. In general it has the same limitations
as ReadOnlyPaths=, see below.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RuntimeDirectory=, StateDirectory=, CacheDirectory=, LogsDirectory=,
ConfigurationDirectory=
These options take a whitespace-separated list of directory
names. The specified directory names must be relative, and may
not include "..". If set, one or more directories by the
specified names will be created (including their parents) below
the locations defined in the following table, when the unit is
started. Also, the corresponding environment variable is defined
with the full path of directories. If multiple directories are
set, then in the environment variable the paths are concatenated
with colon (":").
Table 2. Automatic directory creation and environment variables
┌────────────────────────┬────────────────┬───────────────────────┬──────────────────────────┐
│Directory │ Below path for │ Below path for │ Environment │
│ │ system units │ user units │ variable set │
├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
│RuntimeDirectory= │ /run/ │ $XDG_RUNTIME_DIR │ $RUNTIME_DIRECTORY │
├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
│StateDirectory= │ /var/lib/ │ $XDG_CONFIG_HOME │ $STATE_DIRECTORY │
├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
│CacheDirectory= │ /var/cache/ │ $XDG_CACHE_HOME │ $CACHE_DIRECTORY │
├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
│LogsDirectory= │ /var/log/ │ $XDG_CONFIG_HOME/log/ │ $LOGS_DIRECTORY │
├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
│ConfigurationDirectory= │ /etc/ │ $XDG_CONFIG_HOME │ $CONFIGURATION_DIRECTORY │
└────────────────────────┴────────────────┴───────────────────────┴──────────────────────────┘
In case of RuntimeDirectory= the innermost subdirectories are
removed when the unit is stopped. It is possible to preserve the
specified directories in this case if RuntimeDirectoryPreserve=
is configured to restart or yes (see below). The directories
specified with StateDirectory=, CacheDirectory=, LogsDirectory=,
ConfigurationDirectory= are not removed when the unit is stopped.
Except in case of ConfigurationDirectory=, the innermost
specified directories will be owned by the user and group
specified in User= and Group=. If the specified directories
already exist and their owning user or group do not match the
configured ones, all files and directories below the specified
directories as well as the directories themselves will have their
file ownership recursively changed to match what is configured.
As an optimization, if the specified directories are already
owned by the right user and group, files and directories below of
them are left as-is, even if they do not match what is requested.
The innermost specified directories will have their access mode
adjusted to the what is specified in RuntimeDirectoryMode=,
StateDirectoryMode=, CacheDirectoryMode=, LogsDirectoryMode= and
ConfigurationDirectoryMode=.
These options imply BindPaths= for the specified paths. When
combined with RootDirectory= or RootImage= these paths always
reside on the host and are mounted from there into the unit's
file system namespace.
If DynamicUser= is used in conjunction with StateDirectory=, the
logic for CacheDirectory= and LogsDirectory= is slightly altered:
the directories are created below /var/lib/private,
/var/cache/private and /var/log/private, respectively, which are
host directories made inaccessible to unprivileged users, which
ensures that access to these directories cannot be gained through
dynamic user ID recycling. Symbolic links are created to hide
this difference in behaviour. Both from perspective of the host
and from inside the unit, the relevant directories hence always
appear directly below /var/lib, /var/cache and /var/log.
Use RuntimeDirectory= to manage one or more runtime directories
for the unit and bind their lifetime to the daemon runtime. This
is particularly useful for unprivileged daemons that cannot
create runtime directories in /run due to lack of privileges, and
to make sure the runtime directory is cleaned up automatically
after use. For runtime directories that require more complex or
different configuration or lifetime guarantees, please consider
using tmpfiles.d(5).
The directories defined by these options are always created under
the standard paths used by systemd (/var, /run, /etc, ...). If
the service needs directories in a different location, a
different mechanism has to be used to create them.
tmpfiles.d(5) provides functionality that overlaps with these
options. Using these options is recommended, because the lifetime
of the directories is tied directly to the lifetime of the unit,
and it is not necessary to ensure that the tmpfiles.d
configuration is executed before the unit is started.
To remove any of the directories created by these settings, use
the systemctl clean ... command on the relevant units, see
systemctl(1) for details.
Example: if a system service unit has the following,
RuntimeDirectory=foo/bar baz
the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories /run/foo/bar and
/run/baz except /run/foo are owned by the user and group
specified in User= and Group=, and removed when the service is
stopped.
Example: if a system service unit has the following,
RuntimeDirectory=foo/bar
StateDirectory=aaa/bbb ccc
then the environment variable "RUNTIME_DIRECTORY" is set with
"/run/foo/bar", and "STATE_DIRECTORY" is set with
"/var/lib/aaa/bbb:/var/lib/ccc".
RuntimeDirectoryMode=, StateDirectoryMode=, CacheDirectoryMode=,
LogsDirectoryMode=, ConfigurationDirectoryMode=
Specifies the access mode of the directories specified in
RuntimeDirectory=, StateDirectory=, CacheDirectory=,
LogsDirectory=, or ConfigurationDirectory=, respectively, as an
octal number. Defaults to 0755. See "Permissions" in
path_resolution(7) for a discussion of the meaning of permission
bits.
RuntimeDirectoryPreserve=
Takes a boolean argument or restart. If set to no (the default),
the directories specified in RuntimeDirectory= are always removed
when the service stops. If set to restart the directories are
preserved when the service is both automatically and manually
restarted. Here, the automatic restart means the operation
specified in Restart=, and manual restart means the one triggered
by systemctl restart foo.service. If set to yes, then the
directories are not removed when the service is stopped. Note
that since the runtime directory /run is a mount point of
"tmpfs", then for system services the directories specified in
RuntimeDirectory= are removed when the system is rebooted.
TimeoutCleanSec=
Configures a timeout on the clean-up operation requested through
systemctl clean ..., see systemctl(1) for details. Takes the
usual time values and defaults to infinity, i.e. by default no
timeout is applied. If a timeout is configured the clean
operation will be aborted forcibly when the timeout is reached,
potentially leaving resources on disk.
ReadWritePaths=, ReadOnlyPaths=, InaccessiblePaths=
Sets up a new file system namespace for executed processes. These
options may be used to limit access a process might have to the
file system hierarchy. Each setting takes a space-separated list
of paths relative to the host's root directory (i.e. the system
running the service manager). Note that if paths contain
symlinks, they are resolved relative to the root directory set
with RootDirectory=/RootImage=.
Paths listed in ReadWritePaths= are accessible from within the
namespace with the same access modes as from outside of it. Paths
listed in ReadOnlyPaths= are accessible for reading only, writing
will be refused even if the usual file access controls would
permit this. Nest ReadWritePaths= inside of ReadOnlyPaths= in
order to provide writable subdirectories within read-only
directories. Use ReadWritePaths= in order to allow-list specific
paths for write access if ProtectSystem=strict is used.
Paths listed in InaccessiblePaths= will be made inaccessible for
processes inside the namespace along with everything below them
in the file system hierarchy. This may be more restrictive than
desired, because it is not possible to nest ReadWritePaths=,
ReadOnlyPaths=, BindPaths=, or BindReadOnlyPaths= inside it. For
a more flexible option, see TemporaryFileSystem=.
Non-directory paths may be specified as well. These options may
be specified more than once, in which case all paths listed will
have limited access from within the namespace. If the empty
string is assigned to this option, the specific list is reset,
and all prior assignments have no effect.
Paths in ReadWritePaths=, ReadOnlyPaths= and InaccessiblePaths=
may be prefixed with "-", in which case they will be ignored when
they do not exist. If prefixed with "+" the paths are taken
relative to the root directory of the unit, as configured with
RootDirectory=/RootImage=, instead of relative to the root
directory of the host (see above). When combining "-" and "+" on
the same path make sure to specify "-" first, and "+" second.
Note that these settings will disconnect propagation of mounts
from the unit's processes to the host. This means that this
setting may not be used for services which shall be able to
install mount points in the main mount namespace. For
ReadWritePaths= and ReadOnlyPaths= propagation in the other
direction is not affected, i.e. mounts created on the host
generally appear in the unit processes' namespace, and mounts
removed on the host also disappear there too. In particular, note
that mount propagation from host to unit will result in
unmodified mounts to be created in the unit's namespace, i.e.
writable mounts appearing on the host will be writable in the
unit's namespace too, even when propagated below a path marked
with ReadOnlyPaths=! Restricting access with these options hence
does not extend to submounts of a directory that are created
later on. This means the lock-down offered by that setting is not
complete, and does not offer full protection.
Note that the effect of these settings may be undone by
privileged processes. In order to set up an effective sandboxed
environment for a unit it is thus recommended to combine these
settings with either CapabilityBoundingSet=~CAP_SYS_ADMIN or
SystemCallFilter=~@mount.
These options are only available for system services and are not
supported for services running in per-user instances of the
service manager.
TemporaryFileSystem=
Takes a space-separated list of mount points for temporary file
systems (tmpfs). If set, a new file system namespace is set up
for executed processes, and a temporary file system is mounted on
each mount point. This option may be specified more than once, in
which case temporary file systems are mounted on all listed mount
points. If the empty string is assigned to this option, the list
is reset, and all prior assignments have no effect. Each mount
point may optionally be suffixed with a colon (":") and mount
options such as "size=10%" or "ro". By default, each temporary
file system is mounted with "nodev,strictatime,mode=0755". These
can be disabled by explicitly specifying the corresponding mount
options, e.g., "dev" or "nostrictatime".
This is useful to hide files or directories not relevant to the
processes invoked by the unit, while necessary files or
directories can be still accessed by combining with BindPaths= or
BindReadOnlyPaths=:
Example: if a unit has the following,
TemporaryFileSystem=/var:ro
BindReadOnlyPaths=/var/lib/systemd
then the invoked processes by the unit cannot see any files or
directories under /var except for /var/lib/systemd or its
contents.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
PrivateTmp=
Takes a boolean argument. If true, sets up a new file system
namespace for the executed processes and mounts private /tmp/ and
/var/tmp/ directories inside it that are not shared by processes
outside of the namespace. This is useful to secure access to
temporary files of the process, but makes sharing between
processes via /tmp or /var/tmp impossible. If this is enabled,
all temporary files created by a service in these directories
will be removed after the service is stopped. Defaults to false.
It is possible to run two or more units within the same private
/tmp and /var/tmp namespace by using the JoinsNamespaceOf=
directive, see systemd.unit(5) for details. This setting is
implied if DynamicUser= is set. For this setting the same
restrictions regarding mount propagation and privileges apply as
for ReadOnlyPaths= and related calls, see above. Enabling this
setting has the side effect of adding Requires= and After=
dependencies on all mount units necessary to access /tmp and
/var/tmp. Moreover an implicitly After= ordering on
systemd-tmpfiles-setup.service(8) is added.
Note that the implementation of this setting might be impossible
(for example if mount namespaces are not available), and the unit
should be written in a way that does not solely rely on this
setting for security.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
PrivateDevices=
Takes a boolean argument. If true, sets up a new /dev mount for
the executed processes and only adds API pseudo devices such as
/dev/null, /dev/zero or /dev/random (as well as the pseudo TTY
subsystem) to it, but no physical devices such as /dev/sda,
system memory /dev/mem, system ports /dev/port and others. This
is useful to securely turn off physical device access by the
executed process. Defaults to false. Enabling this option will
install a system call filter to block low-level I/O system calls
that are grouped in the @raw-io set, will also remove CAP_MKNOD
and CAP_SYS_RAWIO from the capability bounding set for the unit
(see above), and set DevicePolicy=closed (see
systemd.resource-control(5) for details). Note that using this
setting will disconnect propagation of mounts from the service to
the host (propagation in the opposite direction continues to
work). This means that this setting may not be used for services
which shall be able to install mount points in the main mount
namespace. The new /dev will be mounted read-only and 'noexec'.
The latter may break old programs which try to set up executable
memory by using mmap(2) of /dev/zero instead of using MAP_ANON.
For this setting the same restrictions regarding mount
propagation and privileges apply as for ReadOnlyPaths= and
related calls, see above. If turned on and if running in user
mode, or in system mode, but without the CAP_SYS_ADMIN capability
(e.g. setting User=), NoNewPrivileges=yes is implied.
Note that the implementation of this setting might be impossible
(for example if mount namespaces are not available), and the unit
should be written in a way that does not solely rely on this
setting for security.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
PrivateNetwork=
Takes a boolean argument. If true, sets up a new network
namespace for the executed processes and configures only the
loopback network device "lo" inside it. No other network devices
will be available to the executed process. This is useful to turn
off network access by the executed process. Defaults to false. It
is possible to run two or more units within the same private
network namespace by using the JoinsNamespaceOf= directive, see
systemd.unit(5) for details. Note that this option will
disconnect all socket families from the host, including
AF_NETLINK and AF_UNIX. Effectively, for AF_NETLINK this means
that device configuration events received from
systemd-udevd.service(8) are not delivered to the unit's
processes. And for AF_UNIX this has the effect that AF_UNIX
sockets in the abstract socket namespace of the host will become
unavailable to the unit's processes (however, those located in
the file system will continue to be accessible).
Note that the implementation of this setting might be impossible
(for example if network namespaces are not available), and the
unit should be written in a way that does not solely rely on this
setting for security.
When this option is used on a socket unit any sockets bound on
behalf of this unit will be bound within a private network
namespace. This may be combined with JoinsNamespaceOf= to listen
on sockets inside of network namespaces of other services.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
NetworkNamespacePath=
Takes an absolute file system path refererring to a Linux network
namespace pseudo-file (i.e. a file like /proc/$PID/ns/net or a
bind mount or symlink to one). When set the invoked processes are
added to the network namespace referenced by that path. The path
has to point to a valid namespace file at the moment the
processes are forked off. If this option is used PrivateNetwork=
has no effect. If this option is used together with
JoinsNamespaceOf= then it only has an effect if this unit is
started before any of the listed units that have PrivateNetwork=
or NetworkNamespacePath= configured, as otherwise the network
namespace of those units is reused.
When this option is used on a socket unit any sockets bound on
behalf of this unit will be bound within the specified network
namespace.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
PrivateUsers=
Takes a boolean argument. If true, sets up a new user namespace
for the executed processes and configures a minimal user and
group mapping, that maps the "root" user and group as well as the
unit's own user and group to themselves and everything else to
the "nobody" user and group. This is useful to securely detach
the user and group databases used by the unit from the rest of
the system, and thus to create an effective sandbox environment.
All files, directories, processes, IPC objects and other
resources owned by users/groups not equaling "root" or the unit's
own will stay visible from within the unit but appear owned by
the "nobody" user and group. If this mode is enabled, all unit
processes are run without privileges in the host user namespace
(regardless if the unit's own user/group is "root" or not).
Specifically this means that the process will have zero process
capabilities on the host's user namespace, but full capabilities
within the service's user namespace. Settings such as
CapabilityBoundingSet= will affect only the latter, and there's
no way to acquire additional capabilities in the host's user
namespace. Defaults to off.
When this setting is set up by a per-user instance of the service
manager, the mapping of the "root" user and group to itself is
omitted (unless the user manager is root). Additionally, in the
per-user instance manager case, the user namespace will be set up
before most other namespaces. This means that combining
PrivateUsers=true with other namespaces will enable use of
features not normally supported by the per-user instances of the
service manager.
This setting is particularly useful in conjunction with
RootDirectory=/RootImage=, as the need to synchronize the user
and group databases in the root directory and on the host is
reduced, as the only users and groups who need to be matched are
"root", "nobody" and the unit's own user and group.
Note that the implementation of this setting might be impossible
(for example if user namespaces are not available), and the unit
should be written in a way that does not solely rely on this
setting for security.
ProtectHostname=
Takes a boolean argument. When set, sets up a new UTS namespace
for the executed processes. In addition, changing hostname or
domainname is prevented. Defaults to off.
Note that the implementation of this setting might be impossible
(for example if UTS namespaces are not available), and the unit
should be written in a way that does not solely rely on this
setting for security.
Note that when this option is enabled for a service hostname
changes no longer propagate from the system into the service, it
is hence not suitable for services that need to take notice of
system hostname changes dynamically.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
ProtectClock=
Takes a boolean argument. If set, writes to the hardware clock or
system clock will be denied. It is recommended to turn this on
for most services that do not need modify the clock. Defaults to
off. Enabling this option removes CAP_SYS_TIME and CAP_WAKE_ALARM
from the capability bounding set for this unit, installs a system
call filter to block calls that can set the clock, and
DeviceAllow=char-rtc r is implied. This ensures /dev/rtc0,
/dev/rtc1, etc. are made read-only to the service. See
systemd.resource-control(5) for the details about DeviceAllow=.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
ProtectKernelTunables=
Takes a boolean argument. If true, kernel variables accessible
through /proc/sys, /sys, /proc/sysrq-trigger,
/proc/latency_stats, /proc/acpi, /proc/timer_stats, /proc/fs and
/proc/irq will be made read-only to all processes of the unit.
Usually, tunable kernel variables should be initialized only at
boot-time, for example with the sysctl.d(5) mechanism. Few
services need to write to these at runtime; it is hence
recommended to turn this on for most services. For this setting
the same restrictions regarding mount propagation and privileges
apply as for ReadOnlyPaths= and related calls, see above.
Defaults to off. If turned on and if running in user mode, or in
system mode, but without the CAP_SYS_ADMIN capability (e.g.
services for which User= is set), NoNewPrivileges=yes is implied.
Note that this option does not prevent indirect changes to kernel
tunables effected by IPC calls to other processes. However,
InaccessiblePaths= may be used to make relevant IPC file system
objects inaccessible. If ProtectKernelTunables= is set,
MountAPIVFS=yes is implied.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
ProtectKernelModules=
Takes a boolean argument. If true, explicit module loading will
be denied. This allows module load and unload operations to be
turned off on modular kernels. It is recommended to turn this on
for most services that do not need special file systems or extra
kernel modules to work. Defaults to off. Enabling this option
removes CAP_SYS_MODULE from the capability bounding set for the
unit, and installs a system call filter to block module system
calls, also /usr/lib/modules is made inaccessible. For this
setting the same restrictions regarding mount propagation and
privileges apply as for ReadOnlyPaths= and related calls, see
above. Note that limited automatic module loading due to user
configuration or kernel mapping tables might still happen as side
effect of requested user operations, both privileged and
unprivileged. To disable module auto-load feature please see
sysctl.d(5) kernel.modules_disabled mechanism and
/proc/sys/kernel/modules_disabled documentation. If turned on and
if running in user mode, or in system mode, but without the
CAP_SYS_ADMIN capability (e.g. setting User=),
NoNewPrivileges=yes is implied.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
ProtectKernelLogs=
Takes a boolean argument. If true, access to the kernel log ring
buffer will be denied. It is recommended to turn this on for most
services that do not need to read from or write to the kernel log
ring buffer. Enabling this option removes CAP_SYSLOG from the
capability bounding set for this unit, and installs a system call
filter to block the syslog(2) system call (not to be confused
with the libc API syslog(3) for userspace logging). The kernel
exposes its log buffer to userspace via /dev/kmsg and /proc/kmsg.
If enabled, these are made inaccessible to all the processes in
the unit.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
ProtectControlGroups=
Takes a boolean argument. If true, the Linux Control Groups (‐
cgroups(7)) hierarchies accessible through /sys/fs/cgroup will be
made read-only to all processes of the unit. Except for container
managers no services should require write access to the control
groups hierarchies; it is hence recommended to turn this on for
most services. For this setting the same restrictions regarding
mount propagation and privileges apply as for ReadOnlyPaths= and
related calls, see above. Defaults to off. If
ProtectControlGroups= is set, MountAPIVFS=yes is implied.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
RestrictAddressFamilies=
Restricts the set of socket address families accessible to the
processes of this unit. Takes a space-separated list of address
family names to allow-list, such as AF_UNIX, AF_INET or AF_INET6.
When prefixed with ~ the listed address families will be applied
as deny list, otherwise as allow list. Note that this restricts
access to the socket(2) system call only. Sockets passed into the
process by other means (for example, by using socket activation
with socket units, see systemd.socket(5)) are unaffected. Also,
sockets created with socketpair() (which creates connected
AF_UNIX sockets only) are unaffected. Note that this option has
no effect on 32-bit x86, s390, s390x, mips, mips-le, ppc, ppc-le,
ppc64, ppc64-le and is ignored (but works correctly on other
ABIs, including x86-64). Note that on systems supporting multiple
ABIs (such as x86/x86-64) it is recommended to turn off
alternative ABIs for services, so that they cannot be used to
circumvent the restrictions of this option. Specifically, it is
recommended to combine this option with
SystemCallArchitectures=native or similar. If running in user
mode, or in system mode, but without the CAP_SYS_ADMIN capability
(e.g. setting User=nobody), NoNewPrivileges=yes is implied. By
default, no restrictions apply, all address families are
accessible to processes. If assigned the empty string, any
previous address family restriction changes are undone. This
setting does not affect commands prefixed with "+".
Use this option to limit exposure of processes to remote access,
in particular via exotic and sensitive network protocols, such as
AF_PACKET. Note that in most cases, the local AF_UNIX address
family should be included in the configured allow list as it is
frequently used for local communication, including for syslog(2)
logging.
RestrictNamespaces=
Restricts access to Linux namespace functionality for the
processes of this unit. For details about Linux namespaces, see
namespaces(7). Either takes a boolean argument, or a
space-separated list of namespace type identifiers. If false (the
default), no restrictions on namespace creation and switching are
made. If true, access to any kind of namespacing is prohibited.
Otherwise, a space-separated list of namespace type identifiers
must be specified, consisting of any combination of: cgroup, ipc,
net, mnt, pid, user and uts. Any namespace type listed is made
accessible to the unit's processes, access to namespace types not
listed is prohibited (allow-listing). By prepending the list with
a single tilde character ("~") the effect may be inverted: only
the listed namespace types will be made inaccessible, all
unlisted ones are permitted (deny-listing). If the empty string
is assigned, the default namespace restrictions are applied,
which is equivalent to false. This option may appear more than
once, in which case the namespace types are merged by OR, or by
AND if the lines are prefixed with "~" (see examples below).
Internally, this setting limits access to the unshare(2),
clone(2) and setns(2) system calls, taking the specified flags
parameters into account. Note that — if this option is used — in
addition to restricting creation and switching of the specified
types of namespaces (or all of them, if true) access to the
setns() system call with a zero flags parameter is prohibited.
This setting is only supported on x86, x86-64, mips, mips-le,
mips64, mips64-le, mips64-n32, mips64-le-n32, ppc64, ppc64-le,
s390 and s390x, and enforces no restrictions on other
architectures. If running in user mode, or in system mode, but
without the CAP_SYS_ADMIN capability (e.g. setting User=),
NoNewPrivileges=yes is implied.
Example: if a unit has the following,
RestrictNamespaces=cgroup ipc
RestrictNamespaces=cgroup net
then cgroup, ipc, and net are set. If the second line is prefixed
with "~", e.g.,
RestrictNamespaces=cgroup ipc
RestrictNamespaces=~cgroup net
then, only ipc is set.
LockPersonality=
Takes a boolean argument. If set, locks down the personality(2)
system call so that the kernel execution domain may not be
changed from the default or the personality selected with
Personality= directive. This may be useful to improve security,
because odd personality emulations may be poorly tested and
source of vulnerabilities. If running in user mode, or in system
mode, but without the CAP_SYS_ADMIN capability (e.g. setting
User=), NoNewPrivileges=yes is implied.
MemoryDenyWriteExecute=
Takes a boolean argument. If set, attempts to create memory
mappings that are writable and executable at the same time, or to
change existing memory mappings to become executable, or mapping
shared memory segments as executable are prohibited.
Specifically, a system call filter is added that rejects mmap(2)
system calls with both PROT_EXEC and PROT_WRITE set, mprotect(2)
or pkey_mprotect(2) system calls with PROT_EXEC set and shmat(2)
system calls with SHM_EXEC set. Note that this option is
incompatible with programs and libraries that generate program
code dynamically at runtime, including JIT execution engines,
executable stacks, and code "trampoline" feature of various C
compilers. This option improves service security, as it makes
harder for software exploits to change running code dynamically.
However, the protection can be circumvented, if the service can
write to a filesystem, which is not mounted with noexec (such as
/dev/shm), or it can use memfd_create(). This can be prevented by
making such file systems inaccessible to the service (e.g.
InaccessiblePaths=/dev/shm) and installing further system call
filters (SystemCallFilter=~memfd_create). Note that this feature
is fully available on x86-64, and partially on x86. Specifically,
the shmat() protection is not available on x86. Note that on
systems supporting multiple ABIs (such as x86/x86-64) it is
recommended to turn off alternative ABIs for services, so that
they cannot be used to circumvent the restrictions of this
option. Specifically, it is recommended to combine this option
with SystemCallArchitectures=native or similar. If running in
user mode, or in system mode, but without the CAP_SYS_ADMIN
capability (e.g. setting User=), NoNewPrivileges=yes is implied.
RestrictRealtime=
Takes a boolean argument. If set, any attempts to enable realtime
scheduling in a process of the unit are refused. This restricts
access to realtime task scheduling policies such as SCHED_FIFO,
SCHED_RR or SCHED_DEADLINE. See sched(7) for details about these
scheduling policies. If running in user mode, or in system mode,
but without the CAP_SYS_ADMIN capability (e.g. setting User=),
NoNewPrivileges=yes is implied. Realtime scheduling policies may
be used to monopolize CPU time for longer periods of time, and
may hence be used to lock up or otherwise trigger
Denial-of-Service situations on the system. It is hence
recommended to restrict access to realtime scheduling to the few
programs that actually require them. Defaults to off.
RestrictSUIDSGID=
Takes a boolean argument. If set, any attempts to set the
set-user-ID (SUID) or set-group-ID (SGID) bits on files or
directories will be denied (for details on these bits see
inode(7)). If running in user mode, or in system mode, but
without the CAP_SYS_ADMIN capability (e.g. setting User=),
NoNewPrivileges=yes is implied. As the SUID/SGID bits are
mechanisms to elevate privileges, and allows users to acquire the
identity of other users, it is recommended to restrict creation
of SUID/SGID files to the few programs that actually require
them. Note that this restricts marking of any type of file system
object with these bits, including both regular files and
directories (where the SGID is a different meaning than for
files, see documentation). This option is implied if DynamicUser=
is enabled. Defaults to off.
RemoveIPC=
Takes a boolean parameter. If set, all System V and POSIX IPC
objects owned by the user and group the processes of this unit
are run as are removed when the unit is stopped. This setting
only has an effect if at least one of User=, Group= and
DynamicUser= are used. It has no effect on IPC objects owned by
the root user. Specifically, this removes System V semaphores, as
well as System V and POSIX shared memory segments and message
queues. If multiple units use the same user or group the IPC
objects are removed when the last of these units is stopped. This
setting is implied if DynamicUser= is set.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
PrivateMounts=
Takes a boolean parameter. If set, the processes of this unit
will be run in their own private file system (mount) namespace
with all mount propagation from the processes towards the host's
main file system namespace turned off. This means any file system
mount points established or removed by the unit's processes will
be private to them and not be visible to the host. However, file
system mount points established or removed on the host will be
propagated to the unit's processes. See mount_namespaces(7) for
details on file system namespaces. Defaults to off.
When turned on, this executes three operations for each invoked
process: a new CLONE_NEWNS namespace is created, after which all
existing mounts are remounted to MS_SLAVE to disable propagation
from the unit's processes to the host (but leaving propagation in
the opposite direction in effect). Finally, the mounts are
remounted again to the propagation mode configured with
MountFlags=, see below.
File system namespaces are set up individually for each process
forked off by the service manager. Mounts established in the
namespace of the process created by ExecStartPre= will hence be
cleaned up automatically as soon as that process exits and will
not be available to subsequent processes forked off for
ExecStart= (and similar applies to the various other commands
configured for units). Similarly, JoinsNamespaceOf= does not
permit sharing kernel mount namespaces between units, it only
enables sharing of the /tmp/ and /var/tmp/ directories.
Other file system namespace unit settings — PrivateMounts=,
PrivateTmp=, PrivateDevices=, ProtectSystem=, ProtectHome=,
ReadOnlyPaths=, InaccessiblePaths=, ReadWritePaths=, ... — also
enable file system namespacing in a fashion equivalent to this
option. Hence it is primarily useful to explicitly request this
behaviour if none of the other settings are used.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
MountFlags=
Takes a mount propagation setting: shared, slave or private,
which controls whether file system mount points in the file
system namespaces set up for this unit's processes will receive
or propagate mounts and unmounts from other file system
namespaces. See mount(2) for details on mount propagation, and
the three propagation flags in particular.
This setting only controls the final propagation setting in
effect on all mount points of the file system namespace created
for each process of this unit. Other file system namespacing unit
settings (see the discussion in PrivateMounts= above) will
implicitly disable mount and unmount propagation from the unit's
processes towards the host by changing the propagation setting of
all mount points in the unit's file system namespace to slave
first. Setting this option to shared does not reestablish
propagation in that case.
If not set – but file system namespaces are enabled through
another file system namespace unit setting – shared mount
propagation is used, but — as mentioned — as slave is applied
first, propagation from the unit's processes to the host is still
turned off.
It is not recommended to use private mount propagation for units,
as this means temporary mounts (such as removable media) of the
host will stay mounted and thus indefinitely busy in forked off
processes, as unmount propagation events won't be received by the
file system namespace of the unit.
Usually, it is best to leave this setting unmodified, and use
higher level file system namespacing options instead, in
particular PrivateMounts=, see above.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
SystemCallFilter=
Takes a space-separated list of system call names. If this
setting is used, all system calls executed by the unit processes
except for the listed ones will result in immediate process
termination with the SIGSYS signal (allow-listing). (See
SystemCallErrorNumber= below for changing the default action). If
the first character of the list is "~", the effect is inverted:
only the listed system calls will result in immediate process
termination (deny-listing). Deny-listed system calls and system
call groups may optionally be suffixed with a colon (":") and
"errno" error number (between 0 and 4095) or errno name such as
EPERM, EACCES or EUCLEAN (see errno(3) for a full list). This
value will be returned when a deny-listed system call is
triggered, instead of terminating the processes immediately. This
value takes precedence over the one given in
SystemCallErrorNumber=, see below. If running in user mode, or in
system mode, but without the CAP_SYS_ADMIN capability (e.g.
setting User=nobody), NoNewPrivileges=yes is implied. This
feature makes use of the Secure Computing Mode 2 interfaces of
the kernel ('seccomp filtering') and is useful for enforcing a
minimal sandboxing environment. Note that the execve, exit,
exit_group, getrlimit, rt_sigreturn, sigreturn system calls and
the system calls for querying time and sleeping are implicitly
allow-listed and do not need to be listed explicitly. This option
may be specified more than once, in which case the filter masks
are merged. If the empty string is assigned, the filter is reset,
all prior assignments will have no effect. This does not affect
commands prefixed with "+".
Note that on systems supporting multiple ABIs (such as
x86/x86-64) it is recommended to turn off alternative ABIs for
services, so that they cannot be used to circumvent the
restrictions of this option. Specifically, it is recommended to
combine this option with SystemCallArchitectures=native or
similar.
Note that strict system call filters may impact execution and
error handling code paths of the service invocation.
Specifically, access to the execve system call is required for
the execution of the service binary — if it is blocked service
invocation will necessarily fail. Also, if execution of the
service binary fails for some reason (for example: missing
service executable), the error handling logic might require
access to an additional set of system calls in order to process
and log this failure correctly. It might be necessary to
temporarily disable system call filters in order to simplify
debugging of such failures.
If you specify both types of this option (i.e. allow-listing and
deny-listing), the first encountered will take precedence and
will dictate the default action (termination or approval of a
system call). Then the next occurrences of this option will add
or delete the listed system calls from the set of the filtered
system calls, depending of its type and the default action. (For
example, if you have started with an allow list rule for read and
write, and right after it add a deny list rule for write, then
write will be removed from the set.)
As the number of possible system calls is large, predefined sets
of system calls are provided. A set starts with "@" character,
followed by name of the set.
Table 3. Currently predefined system call sets
┌────────────────┬───────────────────────────┐
│Set │ Description │
├────────────────┼───────────────────────────┤
│@aio │ Asynchronous I/O (‐ │
│ │ io_setup(2), │
│ │ io_submit(2), and related │
│ │ calls) │
├────────────────┼───────────────────────────┤
│@basic-io │ System calls for basic │
│ │ I/O: reading, writing, │
│ │ seeking, file descriptor │
│ │ duplication and closing │
│ │ (read(2), write(2), and │
│ │ related calls) │
├────────────────┼───────────────────────────┤
│@chown │ Changing file ownership │
│ │ (chown(2), fchownat(2), │
│ │ and related calls) │
├────────────────┼───────────────────────────┤
│@clock │ System calls for changing │
│ │ the system clock (‐ │
│ │ adjtimex(2), │
│ │ settimeofday(2), and │
│ │ related calls) │
├────────────────┼───────────────────────────┤
│@cpu-emulation │ System calls for CPU │
│ │ emulation functionality │
│ │ (vm86(2) and related │
│ │ calls) │
├────────────────┼───────────────────────────┤
│@debug │ Debugging, performance │
│ │ monitoring and tracing │
│ │ functionality (ptrace(2), │
│ │ perf_event_open(2) and │
│ │ related calls) │
├────────────────┼───────────────────────────┤
│@file-system │ File system operations: │
│ │ opening, creating files │
│ │ and directories for read │
│ │ and write, renaming and │
│ │ removing them, reading │
│ │ file properties, or │
│ │ creating hard and │
│ │ symbolic links │
├────────────────┼───────────────────────────┤
│@io-event │ Event loop system calls │
│ │ (poll(2), select(2), │
│ │ epoll(7), eventfd(2) and │
│ │ related calls) │
├────────────────┼───────────────────────────┤
│@ipc │ Pipes, SysV IPC, POSIX │
│ │ Message Queues and other │
│ │ IPC (mq_overview(7), │
│ │ svipc(7)) │
├────────────────┼───────────────────────────┤
│@keyring │ Kernel keyring access (‐ │
│ │ keyctl(2) and related │
│ │ calls) │
├────────────────┼───────────────────────────┤
│@memlock │ Locking of memory in RAM │
│ │ (mlock(2), mlockall(2) │
│ │ and related calls) │
├────────────────┼───────────────────────────┤
│@module │ Loading and unloading of │
│ │ kernel modules (‐ │
│ │ init_module(2), │
│ │ delete_module(2) and │
│ │ related calls) │
├────────────────┼───────────────────────────┤
│@mount │ Mounting and unmounting │
│ │ of file systems (‐ │
│ │ mount(2), chroot(2), and │
│ │ related calls) │
├────────────────┼───────────────────────────┤
│@network-io │ Socket I/O (including │
│ │ local AF_UNIX): │
│ │ socket(7), unix(7) │
├────────────────┼───────────────────────────┤
│@obsolete │ Unusual, obsolete or │
│ │ unimplemented (‐ │
│ │ create_module(2), │
│ │ gtty(2), ...) │
├────────────────┼───────────────────────────┤
│@privileged │ All system calls which │
│ │ need super-user │
│ │ capabilities (‐ │
│ │ capabilities(7)) │
├────────────────┼───────────────────────────┤
│@process │ Process control, │
│ │ execution, namespaceing │
│ │ operations (clone(2), │
│ │ kill(2), namespaces(7), │
│ │ ...) │
├────────────────┼───────────────────────────┤
│@raw-io │ Raw I/O port access (‐ │
│ │ ioperm(2), iopl(2), │
│ │ pciconfig_read(), ...) │
├────────────────┼───────────────────────────┤
│@reboot │ System calls for │
│ │ rebooting and reboot │
│ │ preparation (reboot(2), │
│ │ kexec(), ...) │
├────────────────┼───────────────────────────┤
│@resources │ System calls for changing │
│ │ resource limits, memory │
│ │ and scheduling parameters │
│ │ (setrlimit(2), │
│ │ setpriority(2), ...) │
├────────────────┼───────────────────────────┤
│@setuid │ System calls for changing │
│ │ user ID and group ID │
│ │ credentials, (setuid(2), │
│ │ setgid(2), setresuid(2), │
│ │ ...) │
├────────────────┼───────────────────────────┤
│@signal │ System calls for │
│ │ manipulating and handling │
│ │ process signals (‐ │
│ │ signal(2), │
│ │ sigprocmask(2), ...) │
├────────────────┼───────────────────────────┤
│@swap │ System calls for │
│ │ enabling/disabling swap │
│ │ devices (swapon(2), │
│ │ swapoff(2)) │
├────────────────┼───────────────────────────┤
│@sync │ Synchronizing files and │
│ │ memory to disk (fsync(2), │
│ │ msync(2), and related │
│ │ calls) │
├────────────────┼───────────────────────────┤
│@system-service │ A reasonable set of │
│ │ system calls used by │
│ │ common system services, │
│ │ excluding any special │
│ │ purpose calls. This is │
│ │ the recommended starting │
│ │ point for allow-listing │
│ │ system calls for system │
│ │ services, as it contains │
│ │ what is typically needed │
│ │ by system services, but │
│ │ excludes overly specific │
│ │ interfaces. For example, │
│ │ the following APIs are │
│ │ excluded: "@clock", │
│ │ "@mount", "@swap", │
│ │ "@reboot". │
├────────────────┼───────────────────────────┤
│@timer │ System calls for │
│ │ scheduling operations by │
│ │ time (alarm(2), │
│ │ timer_create(2), ...) │
└────────────────┴───────────────────────────┘
Note, that as new system calls are added to the kernel,
additional system calls might be added to the groups above.
Contents of the sets may also change between systemd versions. In
addition, the list of system calls depends on the kernel version
and architecture for which systemd was compiled. Use
systemd-analyze syscall-filter to list the actual list of system
calls in each filter.
Generally, allow-listing system calls (rather than deny-listing)
is the safer mode of operation. It is recommended to enforce
system call allow lists for all long-running system services.
Specifically, the following lines are a relatively safe basic
choice for the majority of system services:
[Service]
SystemCallFilter=@system-service
SystemCallErrorNumber=EPERM
Note that various kernel system calls are defined redundantly:
there are multiple system calls for executing the same operation.
For example, the pidfd_send_signal() system call may be used to
execute operations similar to what can be done with the older
kill() system call, hence blocking the latter without the former
only provides weak protection. Since new system calls are added
regularly to the kernel as development progresses, keeping system
call deny lists comprehensive requires constant work. It is thus
recommended to use allow-listing instead, which offers the
benefit that new system calls are by default implicitly blocked
until the allow list is updated.
Also note that a number of system calls are required to be
accessible for the dynamic linker to work. The dynamic linker is
required for running most regular programs (specifically: all
dynamic ELF binaries, which is how most distributions build
packaged programs). This means that blocking these system calls
(which include open(), openat() or mmap()) will make most
programs typically shipped with generic distributions unusable.
It is recommended to combine the file system namespacing related
options with SystemCallFilter=~@mount, in order to prohibit the
unit's processes to undo the mappings. Specifically these are the
options PrivateTmp=, PrivateDevices=, ProtectSystem=,
ProtectHome=, ProtectKernelTunables=, ProtectControlGroups=,
ProtectKernelLogs=, ProtectClock=, ReadOnlyPaths=,
InaccessiblePaths= and ReadWritePaths=.
SystemCallErrorNumber=
Takes an "errno" error number (between 1 and 4095) or errno name
such as EPERM, EACCES or EUCLEAN, to return when the system call
filter configured with SystemCallFilter= is triggered, instead of
terminating the process immediately. See errno(3) for a full list
of error codes. When this setting is not used, or when the empty
string is assigned, the process will be terminated immediately
when the filter is triggered.
SystemCallArchitectures=
Takes a space-separated list of architecture identifiers to
include in the system call filter. The known architecture
identifiers are the same as for ConditionArchitecture= described
in systemd.unit(5), as well as x32, mips64-n32, mips64-le-n32,
and the special identifier native. The special identifier native
implicitly maps to the native architecture of the system (or more
precisely: to the architecture the system manager is compiled
for). If running in user mode, or in system mode, but without the
CAP_SYS_ADMIN capability (e.g. setting User=nobody),
NoNewPrivileges=yes is implied. By default, this option is set to
the empty list, i.e. no filtering is applied.
If this setting is used, processes of this unit will only be
permitted to call native system calls, and system calls of the
specified architectures. For the purposes of this option, the x32
architecture is treated as including x86-64 system calls.
However, this setting still fulfills its purpose, as explained
below, on x32.
System call filtering is not equally effective on all
architectures. For example, on x86 filtering of network
socket-related calls is not possible, due to ABI limitations — a
limitation that x86-64 does not have, however. On systems
supporting multiple ABIs at the same time — such as x86/x86-64 —
it is hence recommended to limit the set of permitted system call
architectures so that secondary ABIs may not be used to
circumvent the restrictions applied to the native ABI of the
system. In particular, setting SystemCallArchitectures=native is
a good choice for disabling non-native ABIs.
System call architectures may also be restricted system-wide via
the SystemCallArchitectures= option in the global configuration.
See systemd-system.conf(5) for details.
Environment=
Sets environment variables for executed processes. Takes a
space-separated list of variable assignments. This option may be
specified more than once, in which case all listed variables will
be set. If the same variable is set twice, the later setting will
override the earlier setting. If the empty string is assigned to
this option, the list of environment variables is reset, all
prior assignments have no effect. Variable expansion is not
performed inside the strings, however, specifier expansion is
possible. The $ character has no special meaning. If you need to
assign a value containing spaces or the equals sign to a
variable, use double quotes (") for the assignment.
Example:
Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"
gives three variables "VAR1", "VAR2", "VAR3" with the values
"word1 word2", "word3", "$word 5 6".
See environ(7) for details about environment variables.
Note that environment variables are not suitable for passing
secrets (such as passwords, key material, ...) to service
processes. Environment variables set for a unit are exposed to
unprivileged clients via D-Bus IPC, and generally not understood
as being data that requires protection. Moreover, environment
variables are propagated down the process tree, including across
security boundaries (such as setuid/setgid executables), and
hence might leak to processes that should not have access to the
secret data.
EnvironmentFile=
Similar to Environment= but reads the environment variables from
a text file. The text file should contain new-line-separated
variable assignments. Empty lines, lines without an "="
separator, or lines starting with ; or # will be ignored, which
may be used for commenting. A line ending with a backslash will
be concatenated with the following one, allowing multiline
variable definitions. The parser strips leading and trailing
whitespace from the values of assignments, unless you use double
quotes (").
C escapes[5] are supported, but not most control characters[6].
"\t" and "\n" can be used to insert tabs and newlines within
EnvironmentFile=.
The argument passed should be an absolute filename or wildcard
expression, optionally prefixed with "-", which indicates that if
the file does not exist, it will not be read and no error or
warning message is logged. This option may be specified more than
once in which case all specified files are read. If the empty
string is assigned to this option, the list of file to read is
reset, all prior assignments have no effect.
The files listed with this directive will be read shortly before
the process is executed (more specifically, after all processes
from a previous unit state terminated. This means you can
generate these files in one unit state, and read it with this
option in the next. The files are read from the file system of
the service manager, before any file system changes like bind
mounts take place).
Settings from these files override settings made with
Environment=. If the same variable is set twice from these files,
the files will be read in the order they are specified and the
later setting will override the earlier setting.
PassEnvironment=
Pass environment variables set for the system service manager to
executed processes. Takes a space-separated list of variable
names. This option may be specified more than once, in which case
all listed variables will be passed. If the empty string is
assigned to this option, the list of environment variables to
pass is reset, all prior assignments have no effect. Variables
specified that are not set for the system manager will not be
passed and will be silently ignored. Note that this option is
only relevant for the system service manager, as system services
by default do not automatically inherit any environment variables
set for the service manager itself. However, in case of the user
service manager all environment variables are passed to the
executed processes anyway, hence this option is without effect
for the user service manager.
Variables set for invoked processes due to this setting are
subject to being overridden by those configured with Environment=
or EnvironmentFile=.
C escapes[5] are supported, but not most control characters[6].
"\t" and "\n" can be used to insert tabs and newlines within
EnvironmentFile=.
Example:
PassEnvironment=VAR1 VAR2 VAR3
passes three variables "VAR1", "VAR2", "VAR3" with the values set
for those variables in PID1.
See environ(7) for details about environment variables.
UnsetEnvironment=
Explicitly unset environment variable assignments that would
normally be passed from the service manager to invoked processes
of this unit. Takes a space-separated list of variable names or
variable assignments. This option may be specified more than
once, in which case all listed variables/assignments will be
unset. If the empty string is assigned to this option, the list
of environment variables/assignments to unset is reset. If a
variable assignment is specified (that is: a variable name,
followed by "=", followed by its value), then any environment
variable matching this precise assignment is removed. If a
variable name is specified (that is a variable name without any
following "=" or value), then any assignment matching the
variable name, regardless of its value is removed. Note that the
effect of UnsetEnvironment= is applied as final step when the
environment list passed to executed processes is compiled. That
means it may undo assignments from any configuration source,
including assignments made through Environment= or
EnvironmentFile=, inherited from the system manager's global set
of environment variables, inherited via PassEnvironment=, set by
the service manager itself (such as $NOTIFY_SOCKET and such), or
set by a PAM module (in case PAMName= is used).
See environ(7) for details about environment variables.
StandardInput=
Controls where file descriptor 0 (STDIN) of the executed
processes is connected to. Takes one of null, tty, tty-force,
tty-fail, data, file:path, socket or fd:name.
If null is selected, standard input will be connected to
/dev/null, i.e. all read attempts by the process will result in
immediate EOF.
If tty is selected, standard input is connected to a TTY (as
configured by TTYPath=, see below) and the executed process
becomes the controlling process of the terminal. If the terminal
is already being controlled by another process, the executed
process waits until the current controlling process releases the
terminal.
tty-force is similar to tty, but the executed process is
forcefully and immediately made the controlling process of the
terminal, potentially removing previous controlling processes
from the terminal.
tty-fail is similar to tty, but if the terminal already has a
controlling process start-up of the executed process fails.
The data option may be used to configure arbitrary textual or
binary data to pass via standard input to the executed process.
The data to pass is configured via
StandardInputText=/StandardInputData= (see below). Note that the
actual file descriptor type passed (memory file, regular file,
UNIX pipe, ...) might depend on the kernel and available
privileges. In any case, the file descriptor is read-only, and
when read returns the specified data followed by EOF.
The file:path option may be used to connect a specific file
system object to standard input. An absolute path following the
":" character is expected, which may refer to a regular file, a
FIFO or special file. If an AF_UNIX socket in the file system is
specified, a stream socket is connected to it. The latter is
useful for connecting standard input of processes to arbitrary
system services.
The socket option is valid in socket-activated services only, and
requires the relevant socket unit file (see systemd.socket(5) for
details) to have Accept=yes set, or to specify a single socket
only. If this option is set, standard input will be connected to
the socket the service was activated from, which is primarily
useful for compatibility with daemons designed for use with the
traditional inetd(8) socket activation daemon.
The fd:name option connects standard input to a specific, named
file descriptor provided by a socket unit. The name may be
specified as part of this option, following a ":" character (e.g.
"fd:foobar"). If no name is specified, the name "stdin" is
implied (i.e. "fd" is equivalent to "fd:stdin"). At least one
socket unit defining the specified name must be provided via the
Sockets= option, and the file descriptor name may differ from the
name of its containing socket unit. If multiple matches are
found, the first one will be used. See FileDescriptorName= in
systemd.socket(5) for more details about named file descriptors
and their ordering.
This setting defaults to null.
StandardOutput=
Controls where file descriptor 1 (stdout) of the executed
processes is connected to. Takes one of inherit, null, tty,
journal, kmsg, journal+console, kmsg+console, file:path,
append:path, socket or fd:name.
inherit duplicates the file descriptor of standard input for
standard output.
null connects standard output to /dev/null, i.e. everything
written to it will be lost.
tty connects standard output to a tty (as configured via
TTYPath=, see below). If the TTY is used for output only, the
executed process will not become the controlling process of the
terminal, and will not fail or wait for other processes to
release the terminal.
journal connects standard output with the journal, which is
accessible via journalctl(1). Note that everything that is
written to kmsg (see below) is implicitly stored in the journal
as well, the specific option listed below is hence a superset of
this one. (Also note that any external, additional syslog daemons
receive their log data from the journal, too, hence this is the
option to use when logging shall be processed with such a
daemon.)
kmsg connects standard output with the kernel log buffer which is
accessible via dmesg(1), in addition to the journal. The journal
daemon might be configured to send all logs to kmsg anyway, in
which case this option is no different from journal.
journal+console and kmsg+console work in a similar way as the two
options above but copy the output to the system console as well.
The file:path option may be used to connect a specific file
system object to standard output. The semantics are similar to
the same option of StandardInput=, see above. If path refers to a
regular file on the filesystem, it is opened (created if it
doesn't exist yet) for writing at the beginning of the file, but
without truncating it. If standard input and output are directed
to the same file path, it is opened only once, for reading as
well as writing and duplicated. This is particularly useful when
the specified path refers to an AF_UNIX socket in the file
system, as in that case only a single stream connection is
created for both input and output.
append:path is similar to file:path above, but it opens the file
in append mode.
socket connects standard output to a socket acquired via socket
activation. The semantics are similar to the same option of
StandardInput=, see above.
The fd:name option connects standard output to a specific, named
file descriptor provided by a socket unit. A name may be
specified as part of this option, following a ":" character (e.g.
"fd:foobar"). If no name is specified, the name "stdout" is
implied (i.e. "fd" is equivalent to "fd:stdout"). At least one
socket unit defining the specified name must be provided via the
Sockets= option, and the file descriptor name may differ from the
name of its containing socket unit. If multiple matches are
found, the first one will be used. See FileDescriptorName= in
systemd.socket(5) for more details about named descriptors and
their ordering.
If the standard output (or error output, see below) of a unit is
connected to the journal or the kernel log buffer, the unit will
implicitly gain a dependency of type After= on
systemd-journald.socket (also see the "Implicit Dependencies"
section above). Also note that in this case stdout (or stderr,
see below) will be an AF_UNIX stream socket, and not a pipe or
FIFO that can be re-opened. This means when executing shell
scripts the construct echo "hello" > /dev/stderr for writing text
to stderr will not work. To mitigate this use the construct echo
"hello" >&2 instead, which is mostly equivalent and avoids this
pitfall.
This setting defaults to the value set with
DefaultStandardOutput= in systemd-system.conf(5), which defaults
to journal. Note that setting this parameter might result in
additional dependencies to be added to the unit (see above).
StandardError=
Controls where file descriptor 2 (stderr) of the executed
processes is connected to. The available options are identical to
those of StandardOutput=, with some exceptions: if set to inherit
the file descriptor used for standard output is duplicated for
standard error, while fd:name will use a default file descriptor
name of "stderr".
This setting defaults to the value set with DefaultStandardError=
in systemd-system.conf(5), which defaults to inherit. Note that
setting this parameter might result in additional dependencies to
be added to the unit (see above).
StandardInputText=, StandardInputData=
Configures arbitrary textual or binary data to pass via file
descriptor 0 (STDIN) to the executed processes. These settings
have no effect unless StandardInput= is set to data. Use this
option to embed process input data directly in the unit file.
StandardInputText= accepts arbitrary textual data. C-style
escapes for special characters as well as the usual
"%"-specifiers are resolved. Each time this setting is used the
specified text is appended to the per-unit data buffer, followed
by a newline character (thus every use appends a new line to the
end of the buffer). Note that leading and trailing whitespace of
lines configured with this option is removed. If an empty line is
specified the buffer is cleared (hence, in order to insert an
empty line, add an additional "\n" to the end or beginning of a
line).
StandardInputData= accepts arbitrary binary data, encoded in
Base64[7]. No escape sequences or specifiers are resolved. Any
whitespace in the encoded version is ignored during decoding.
Note that StandardInputText= and StandardInputData= operate on
the same data buffer, and may be mixed in order to configure both
binary and textual data for the same input stream. The textual or
binary data is joined strictly in the order the settings appear
in the unit file. Assigning an empty string to either will reset
the data buffer.
Please keep in mind that in order to maintain readability long
unit file settings may be split into multiple lines, by suffixing
each line (except for the last) with a "\" character (see
systemd.unit(5) for details). This is particularly useful for
large data configured with these two options. Example:
...
StandardInput=data
StandardInputData=SWNrIHNpdHplIGRhIHVuJyBlc3NlIEtsb3BzLAp1ZmYgZWVtYWwga2xvcHAncy4KSWNrIGtpZWtl \
LCBzdGF1bmUsIHd1bmRyZSBtaXIsCnVmZiBlZW1hbCBqZWh0IHNlIHVmZiBkaWUgVMO8ci4KTmFu \
dSwgZGVuayBpY2ssIGljayBkZW5rIG5hbnUhCkpldHogaXNzZSB1ZmYsIGVyc2NodCB3YXIgc2Ug \
enUhCkljayBqZWhlIHJhdXMgdW5kIGJsaWNrZSDigJQKdW5kIHdlciBzdGVodCBkcmF1w59lbj8g \
SWNrZSEK
...
LogLevelMax=
Configures filtering by log level of log messages generated by
this unit. Takes a syslog log level, one of emerg (lowest log
level, only highest priority messages), alert, crit, err,
warning, notice, info, debug (highest log level, also lowest
priority messages). See syslog(3) for details. By default no
filtering is applied (i.e. the default maximum log level is
debug). Use this option to configure the logging system to drop
log messages of a specific service above the specified level. For
example, set LogLevelMax=info in order to turn off debug logging
of a particularly chatty unit. Note that the configured level is
applied to any log messages written by any of the processes
belonging to this unit, sent via any supported logging protocol.
The filtering is applied early in the logging pipeline, before
any kind of further processing is done. Moreover, messages which
pass through this filter successfully might still be dropped by
filters applied at a later stage in the logging subsystem. For
example, MaxLevelStore= configured in journald.conf(5) might
prohibit messages of higher log levels to be stored on disk, even
though the per-unit LogLevelMax= permitted it to be processed.
LogExtraFields=
Configures additional log metadata fields to include in all log
records generated by processes associated with this unit. This
setting takes one or more journal field assignments in the format
"FIELD=VALUE" separated by whitespace. See
systemd.journal-fields(7) for details on the journal field
concept. Even though the underlying journal implementation
permits binary field values, this setting accepts only valid
UTF-8 values. To include space characters in a journal field
value, enclose the assignment in double quotes ("). The usual
specifiers are expanded in all assignments (see below). Note that
this setting is not only useful for attaching additional metadata
to log records of a unit, but given that all fields and values
are indexed may also be used to implement cross-unit log record
matching. Assign an empty string to reset the list.
LogRateLimitIntervalSec=, LogRateLimitBurst=
Configures the rate limiting that is applied to messages
generated by this unit. If, in the time interval defined by
LogRateLimitIntervalSec=, more messages than specified in
LogRateLimitBurst= are logged by a service, all further messages
within the interval are dropped until the interval is over. A
message about the number of dropped messages is generated. The
time specification for LogRateLimitIntervalSec= may be specified
in the following units: "s", "min", "h", "ms", "us" (see
systemd.time(7) for details). The default settings are set by
RateLimitIntervalSec= and RateLimitBurst= configured in
journald.conf(5).
LogNamespace=
Run the unit's processes in the specified journal namespace.
Expects a short user-defined string identifying the namespace. If
not used the processes of the service are run in the default
journal namespace, i.e. their log stream is collected and
processed by systemd-journald.service. If this option is used any
log data generated by processes of this unit (regardless if via
the syslog(), journal native logging or stdout/stderr logging) is
collected and processed by an instance of the
systemd-journald@.service template unit, which manages the
specified namespace. The log data is stored in a data store
independent from the default log namespace's data store. See
systemd-journald.service(8) for details about journal namespaces.
Internally, journal namespaces are implemented through Linux
mount namespacing and over-mounting the directory that contains
the relevant AF_UNIX sockets used for logging in the unit's mount
namespace. Since mount namespaces are used this setting
disconnects propagation of mounts from the unit's processes to
the host, similar to how ReadOnlyPaths= and similar settings (see
above) work. Journal namespaces may hence not be used for
services that need to establish mount points on the host.
When this option is used the unit will automatically gain
ordering and requirement dependencies on the two socket units
associated with the systemd-journald@.service instance so that
they are automatically established prior to the unit starting up.
Note that when this option is used log output of this service
does not appear in the regular journalctl(1) output, unless the
--namespace= option is used.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
SyslogIdentifier=
Sets the process name ("syslog tag") to prefix log lines sent to
the logging system or the kernel log buffer with. If not set,
defaults to the process name of the executed process. This option
is only useful when StandardOutput= or StandardError= are set to
journal or kmsg (or to the same settings in combination with
+console) and only applies to log messages written to stdout or
stderr.
SyslogFacility=
Sets the syslog facility identifier to use when logging. One of
kern, user, mail, daemon, auth, syslog, lpr, news, uucp, cron,
authpriv, ftp, local0, local1, local2, local3, local4, local5,
local6 or local7. See syslog(3) for details. This option is only
useful when StandardOutput= or StandardError= are set to journal
or kmsg (or to the same settings in combination with +console),
and only applies to log messages written to stdout or stderr.
Defaults to daemon.
SyslogLevel=
The default syslog log level to use when logging to the logging
system or the kernel log buffer. One of emerg, alert, crit, err,
warning, notice, info, debug. See syslog(3) for details. This
option is only useful when StandardOutput= or StandardError= are
set to journal or kmsg (or to the same settings in combination
with +console), and only applies to log messages written to
stdout or stderr. Note that individual lines output by executed
processes may be prefixed with a different log level which can be
used to override the default log level specified here. The
interpretation of these prefixes may be disabled with
SyslogLevelPrefix=, see below. For details, see sd-daemon(3).
Defaults to info.
SyslogLevelPrefix=
Takes a boolean argument. If true and StandardOutput= or
StandardError= are set to journal or kmsg (or to the same
settings in combination with +console), log lines written by the
executed process that are prefixed with a log level will be
processed with this log level set but the prefix removed. If set
to false, the interpretation of these prefixes is disabled and
the logged lines are passed on as-is. This only applies to log
messages written to stdout or stderr. For details about this
prefixing see sd-daemon(3). Defaults to true.
TTYPath=
Sets the terminal device node to use if standard input, output,
or error are connected to a TTY (see above). Defaults to
/dev/console.
TTYReset=
Reset the terminal device specified with TTYPath= before and
after execution. Defaults to "no".
TTYVHangup=
Disconnect all clients which have opened the terminal device
specified with TTYPath= before and after execution. Defaults to
"no".
TTYVTDisallocate=
If the terminal device specified with TTYPath= is a virtual
console terminal, try to deallocate the TTY before and after
execution. This ensures that the screen and scrollback buffer is
cleared. Defaults to "no".
UtmpIdentifier=
Takes a four character identifier string for an utmp(5) and wtmp
entry for this service. This should only be set for services such
as getty implementations (such as agetty(8)) where utmp/wtmp
entries must be created and cleared before and after execution,
or for services that shall be executed as if they were run by a
getty process (see below). If the configured string is longer
than four characters, it is truncated and the terminal four
characters are used. This setting interprets %I style string
replacements. This setting is unset by default, i.e. no utmp/wtmp
entries are created or cleaned up for this service.
UtmpMode=
Takes one of "init", "login" or "user". If UtmpIdentifier= is
set, controls which type of utmp(5)/wtmp entries for this service
are generated. This setting has no effect unless UtmpIdentifier=
is set too. If "init" is set, only an INIT_PROCESS entry is
generated and the invoked process must implement a
getty-compatible utmp/wtmp logic. If "login" is set, first an
INIT_PROCESS entry, followed by a LOGIN_PROCESS entry is
generated. In this case, the invoked process must implement a
login(1)-compatible utmp/wtmp logic. If "user" is set, first an
INIT_PROCESS entry, then a LOGIN_PROCESS entry and finally a
USER_PROCESS entry is generated. In this case, the invoked
process may be any process that is suitable to be run as session
leader. Defaults to "init".
Processes started by the service manager are executed with an
environment variable block assembled from multiple sources. Processes
started by the system service manager generally do not inherit
environment variables set for the service manager itself (but this
may be altered via PassEnvironment=), but processes started by the
user service manager instances generally do inherit all environment
variables set for the service manager itself.
For each invoked process the list of environment variables set is
compiled from the following sources:
· Variables globally configured for the service manager, using the
DefaultEnvironment= setting in systemd-system.conf(5), the kernel
command line option systemd.setenv= (see systemd(1)) or via
systemctl set-environment (see systemctl(1)).
· Variables defined by the service manager itself (see the list
below)
· Variables set in the service manager's own environment variable
block (subject to PassEnvironment= for the system service
manager)
· Variables set via Environment= in the unit file
· Variables read from files specified via EnvironmentFile= in the
unit file
· Variables set by any PAM modules in case PAMName= is in effect,
cf. pam_env(8)
If the same environment variables are set by multiple of these
sources, the later source — according to the order of the list above
— wins. Note that as final step all variables listed in
UnsetEnvironment= are removed again from the compiled environment
variable list, immediately before it is passed to the executed
process.
The following environment variables are set or propagated by the
service manager for each invoked process:
$PATH
Colon-separated list of directories to use when launching
executables. systemd uses a fixed value of
"/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin" in the system
manager. When compiled for systems with "unmerged /usr" (/bin is
not a symlink to /usr/bin), ":/sbin:/bin" is appended. In case of
the the user manager, a different path may be configured by the
distribution. It is recommended to not rely on the order of
entries, and have only one program with a given name in $PATH.
$LANG
Locale. Can be set in locale.conf(5) or on the kernel command
line (see systemd(1) and kernel-command-line(7)).
$USER, $LOGNAME, $HOME, $SHELL
User name (twice), home directory, and the login shell. The
variables are set for the units that have User= set, which
includes user systemd instances. See passwd(5).
$INVOCATION_ID
Contains a randomized, unique 128bit ID identifying each runtime
cycle of the unit, formatted as 32 character hexadecimal string.
A new ID is assigned each time the unit changes from an inactive
state into an activating or active state, and may be used to
identify this specific runtime cycle, in particular in data
stored offline, such as the journal. The same ID is passed to all
processes run as part of the unit.
$XDG_RUNTIME_DIR
The directory to use for runtime objects (such as IPC objects)
and volatile state. Set for all services run by the user systemd
instance, as well as any system services that use PAMName= with a
PAM stack that includes pam_systemd. See below and pam_systemd(8)
for more information.
$RUNTIME_DIRECTORY, $STATE_DIRECTORY, $CACHE_DIRECTORY,
$LOGS_DIRECTORY, $CONFIGURATION_DIRECTORY
Absolute paths to the directories defined with RuntimeDirectory=,
StateDirectory=, CacheDirectory=, LogsDirectory=, and
ConfigurationDirectory= when those settings are used.
$MAINPID
The PID of the unit's main process if it is known. This is only
set for control processes as invoked by ExecReload= and similar.
$MANAGERPID
The PID of the user systemd instance, set for processes spawned
by it.
$LISTEN_FDS, $LISTEN_PID, $LISTEN_FDNAMES
Information about file descriptors passed to a service for socket
activation. See sd_listen_fds(3).
$NOTIFY_SOCKET
The socket sd_notify() talks to. See sd_notify(3).
$WATCHDOG_PID, $WATCHDOG_USEC
Information about watchdog keep-alive notifications. See
sd_watchdog_enabled(3).
$TERM
Terminal type, set only for units connected to a terminal
(StandardInput=tty, StandardOutput=tty, or StandardError=tty).
See termcap(5).
$LOG_NAMESPACE
If the LogNamespace= service setting is used, contains name of
the selected logging namespace.
$JOURNAL_STREAM
If the standard output or standard error output of the executed
processes are connected to the journal (for example, by setting
StandardError=journal) $JOURNAL_STREAM contains the device and
inode numbers of the connection file descriptor, formatted in
decimal, separated by a colon (":"). This permits invoked
processes to safely detect whether their standard output or
standard error output are connected to the journal. The device
and inode numbers of the file descriptors should be compared with
the values set in the environment variable to determine whether
the process output is still connected to the journal. Note that
it is generally not sufficient to only check whether
$JOURNAL_STREAM is set at all as services might invoke external
processes replacing their standard output or standard error
output, without unsetting the environment variable.
If both standard output and standard error of the executed
processes are connected to the journal via a stream socket, this
environment variable will contain information about the standard
error stream, as that's usually the preferred destination for log
data. (Note that typically the same stream is used for both
standard output and standard error, hence very likely the
environment variable contains device and inode information
matching both stream file descriptors.)
This environment variable is primarily useful to allow services
to optionally upgrade their used log protocol to the native
journal protocol (using sd_journal_print(3) and other functions)
if their standard output or standard error output is connected to
the journal anyway, thus enabling delivery of structured metadata
along with logged messages.
$SERVICE_RESULT
Only defined for the service unit type, this environment variable
is passed to all ExecStop= and ExecStopPost= processes, and
encodes the service "result". Currently, the following values are
defined:
Table 4. Defined $SERVICE_RESULT values
┌──────────────────┬───────────────────────────┐
│Value │ Meaning │
├──────────────────┼───────────────────────────┤
│"success" │ The service ran │
│ │ successfully and exited │
│ │ cleanly. │
├──────────────────┼───────────────────────────┤
│"protocol" │ A protocol violation │
│ │ occurred: the service did │
│ │ not take the steps │
│ │ required by its unit │
│ │ configuration │
│ │ (specifically what is │
│ │ configured in its Type= │
│ │ setting). │
├──────────────────┼───────────────────────────┤
│"timeout" │ One of the steps timed │
│ │ out. │
├──────────────────┼───────────────────────────┤
│"exit-code" │ Service process exited │
│ │ with a non-zero exit │
│ │ code; see $EXIT_CODE │
│ │ below for the actual exit │
│ │ code returned. │
├──────────────────┼───────────────────────────┤
│"signal" │ A service process was │
│ │ terminated abnormally by │
│ │ a signal, without dumping │
│ │ core. See $EXIT_CODE │
│ │ below for the actual │
│ │ signal causing the │
│ │ termination. │
├──────────────────┼───────────────────────────┤
│"core-dump" │ A service process │
│ │ terminated abnormally │
│ │ with a signal and dumped │
│ │ core. See $EXIT_CODE │
│ │ below for the signal │
│ │ causing the termination. │
├──────────────────┼───────────────────────────┤
│"watchdog" │ Watchdog keep-alive ping │
│ │ was enabled for the │
│ │ service, but the deadline │
│ │ was missed. │
├──────────────────┼───────────────────────────┤
│"start-limit-hit" │ A start limit was defined │
│ │ for the unit and it was │
│ │ hit, causing the unit to │
│ │ fail to start. See │
│ │ systemd.unit(5)'s │
│ │ StartLimitIntervalSec= │
│ │ and StartLimitBurst= for │
│ │ details. │
├──────────────────┼───────────────────────────┤
│"resources" │ A catch-all condition in │
│ │ case a system operation │
│ │ failed. │
└──────────────────┴───────────────────────────┘
This environment variable is useful to monitor failure or
successful termination of a service. Even though this variable is
available in both ExecStop= and ExecStopPost=, it is usually a
better choice to place monitoring tools in the latter, as the
former is only invoked for services that managed to start up
correctly, and the latter covers both services that failed during
their start-up and those which failed during their runtime.
$EXIT_CODE, $EXIT_STATUS
Only defined for the service unit type, these environment
variables are passed to all ExecStop=, ExecStopPost= processes
and contain exit status/code information of the main process of
the service. For the precise definition of the exit code and
status, see wait(2). $EXIT_CODE is one of "exited", "killed",
"dumped". $EXIT_STATUS contains the numeric exit code formatted
as string if $EXIT_CODE is "exited", and the signal name in all
other cases. Note that these environment variables are only set
if the service manager succeeded to start and identify the main
process of the service.
Table 5. Summary of possible service result variable values
┌──────────────────┬──────────────────┬─────────────────────┐
│$SERVICE_RESULT │ $EXIT_CODE │ $EXIT_STATUS │
├──────────────────┼──────────────────┼─────────────────────┤
│"success" │ "killed" │ "HUP", "INT", │
│ │ │ "TERM", "PIPE" │
│ ├──────────────────┼─────────────────────┤
│ │ "exited" │ "0" │
├──────────────────┼──────────────────┼─────────────────────┤
│"protocol" │ not set │ not set │
│ ├──────────────────┼─────────────────────┤
│ │ "exited" │ "0" │
├──────────────────┼──────────────────┼─────────────────────┤
│"timeout" │ "killed" │ "TERM", "KILL" │
│ ├──────────────────┼─────────────────────┤
│ │ "exited" │ "0", "1", "2", "3", │
│ │ │ ..., "255" │
├──────────────────┼──────────────────┼─────────────────────┤
│"exit-code" │ "exited" │ "1", "2", "3", ..., │
│ │ │ "255" │
├──────────────────┼──────────────────┼─────────────────────┤
│"signal" │ "killed" │ "HUP", "INT", │
│ │ │ "KILL", ... │
├──────────────────┼──────────────────┼─────────────────────┤
│"core-dump" │ "dumped" │ "ABRT", "SEGV", │
│ │ │ "QUIT", ... │
├──────────────────┼──────────────────┼─────────────────────┤
│"watchdog" │ "dumped" │ "ABRT" │
│ ├──────────────────┼─────────────────────┤
│ │ "killed" │ "TERM", "KILL" │
│ ├──────────────────┼─────────────────────┤
│ │ "exited" │ "0", "1", "2", "3", │
│ │ │ ..., "255" │
├──────────────────┼──────────────────┼─────────────────────┤
│"exec-condition" │ "exited" │ "1", "2", "3", "4", │
│ │ │ ..., "254" │
├──────────────────┼──────────────────┼─────────────────────┤
│"oom-kill" │ "killed" │ "TERM", "KILL" │
├──────────────────┼──────────────────┼─────────────────────┤
│"start-limit-hit" │ not set │ not set │
├──────────────────┼──────────────────┼─────────────────────┤
│"resources" │ any of the above │ any of the above │
├──────────────────┴──────────────────┴─────────────────────┤
│Note: the process may be also terminated by a signal not │
│sent by systemd. In particular the process may send an │
│arbitrary signal to itself in a handler for any of the │
│non-maskable signals. Nevertheless, in the "timeout" and │
│"watchdog" rows above only the signals that systemd sends │
│have been included. Moreover, using SuccessExitStatus= │
│additional exit statuses may be declared to indicate │
│clean termination, which is not reflected by this table. │
└───────────────────────────────────────────────────────────┘
$PIDFILE
The path to the configured PID file, in case the process is
forked off on behalf of a service that uses the PIDFile= setting,
see systemd.service(5) for details. Service code may use this
environment variable to automatically generate a PID file at the
location configured in the unit file. This field is set to an
absolute path in the file system.
For system services, when PAMName= is enabled and pam_systemd is part
of the selected PAM stack, additional environment variables defined
by systemd may be set for services. Specifically, these are
$XDG_SEAT, $XDG_VTNR, see pam_systemd(8) for details.
When invoking a unit process the service manager possibly fails to
apply the execution parameters configured with the settings above. In
that case the already created service process will exit with a
non-zero exit code before the configured command line is executed.
(Or in other words, the child process possibly exits with these error
codes, after having been created by the fork(2) system call, but
before the matching execve(2) system call is called.) Specifically,
exit codes defined by the C library, by the LSB specification and by
the systemd service manager itself are used.
The following basic service exit codes are defined by the C library.
Table 6. Basic C library exit codes
┌──────────┬───────────────┬────────────────────┐
│Exit Code │ Symbolic Name │ Description │
├──────────┼───────────────┼────────────────────┤
│0 │ EXIT_SUCCESS │ Generic success │
│ │ │ code. │
├──────────┼───────────────┼────────────────────┤
│1 │ EXIT_FAILURE │ Generic failure or │
│ │ │ unspecified error. │
└──────────┴───────────────┴────────────────────┘
The following service exit codes are defined by the LSB
specification[8].
Table 7. LSB service exit codes
┌──────────┬──────────────────────┬────────────────────┐
│Exit Code │ Symbolic Name │ Description │
├──────────┼──────────────────────┼────────────────────┤
│2 │ EXIT_INVALIDARGUMENT │ Invalid or excess │
│ │ │ arguments. │
├──────────┼──────────────────────┼────────────────────┤
│3 │ EXIT_NOTIMPLEMENTED │ Unimplemented │
│ │ │ feature. │
├──────────┼──────────────────────┼────────────────────┤
│4 │ EXIT_NOPERMISSION │ The user has │
│ │ │ insufficient │
│ │ │ privileges. │
├──────────┼──────────────────────┼────────────────────┤
│5 │ EXIT_NOTINSTALLED │ The program is not │
│ │ │ installed. │
├──────────┼──────────────────────┼────────────────────┤
│6 │ EXIT_NOTCONFIGURED │ The program is not │
│ │ │ configured. │
├──────────┼──────────────────────┼────────────────────┤
│7 │ EXIT_NOTRUNNING │ The program is not │
│ │ │ running. │
└──────────┴──────────────────────┴────────────────────┘
The LSB specification suggests that error codes 200 and above are
reserved for implementations. Some of them are used by the service
manager to indicate problems during process invocation:
Table 8. systemd-specific exit codes
┌──────────┬──────────────────────────────┬─────────────────────────────────────────────┐
│Exit Code │ Symbolic Name │ Description │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│200 │ EXIT_CHDIR │ Changing to the │
│ │ │ requested working │
│ │ │ directory failed. │
│ │ │ See │
│ │ │ WorkingDirectory= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│201 │ EXIT_NICE │ Failed to set up │
│ │ │ process scheduling │
│ │ │ priority (nice │
│ │ │ level). See Nice= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│202 │ EXIT_FDS │ Failed to close │
│ │ │ unwanted file │
│ │ │ descriptors, or to │
│ │ │ adjust passed file │
│ │ │ descriptors. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│203 │ EXIT_EXEC │ The actual process │
│ │ │ execution failed │
│ │ │ (specifically, the │
│ │ │ execve(2) system │
│ │ │ call). Most likely │
│ │ │ this is caused by a │
│ │ │ missing or │
│ │ │ non-accessible │
│ │ │ executable file. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│204 │ EXIT_MEMORY │ Failed to perform │
│ │ │ an action due to │
│ │ │ memory shortage. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│205 │ EXIT_LIMITS │ Failed to adjust │
│ │ │ resource limits. │
│ │ │ See LimitCPU= and │
│ │ │ related settings │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│206 │ EXIT_OOM_ADJUST │ Failed to adjust │
│ │ │ the OOM setting. │
│ │ │ See OOMScoreAdjust= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│207 │ EXIT_SIGNAL_MASK │ Failed to set │
│ │ │ process signal │
│ │ │ mask. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│208 │ EXIT_STDIN │ Failed to set up │
│ │ │ standard input. See │
│ │ │ StandardInput= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│209 │ EXIT_STDOUT │ Failed to set up │
│ │ │ standard output. │
│ │ │ See StandardOutput= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│210 │ EXIT_CHROOT │ Failed to change │
│ │ │ root directory (‐ │
│ │ │ chroot(2)). See │
│ │ │ RootDirectory=/RootImage= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│211 │ EXIT_IOPRIO │ Failed to set up IO │
│ │ │ scheduling priority. See │
│ │ │ IOSchedulingClass=/IOSchedulingPriority= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│212 │ EXIT_TIMERSLACK │ Failed to set up timer slack. See │
│ │ │ TimerSlackNSec= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│213 │ EXIT_SECUREBITS │ Failed to set process secure bits. See │
│ │ │ SecureBits= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│214 │ EXIT_SETSCHEDULER │ Failed to set up CPU scheduling. See │
│ │ │ CPUSchedulingPolicy=/CPUSchedulingPriority= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│215 │ EXIT_CPUAFFINITY │ Failed to set up CPU affinity. See │
│ │ │ CPUAffinity= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│216 │ EXIT_GROUP │ Failed to determine or change group │
│ │ │ credentials. See │
│ │ │ Group=/SupplementaryGroups= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│217 │ EXIT_USER │ Failed to determine or change user │
│ │ │ credentials, or to set up user namespacing. │
│ │ │ See User=/PrivateUsers= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│218 │ EXIT_CAPABILITIES │ Failed to drop capabilities, or apply │
│ │ │ ambient capabilities. See │
│ │ │ CapabilityBoundingSet=/AmbientCapabilities= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│219 │ EXIT_CGROUP │ Setting up the service control group │
│ │ │ failed. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│220 │ EXIT_SETSID │ Failed to create new process session. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│221 │ EXIT_CONFIRM │ Execution has been cancelled by the user. │
│ │ │ See the systemd.confirm_spawn= kernel │
│ │ │ command line setting on │
│ │ │ kernel-command-line(7) for details. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│222 │ EXIT_STDERR │ Failed to set up standard error output. See │
│ │ │ StandardError= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│224 │ EXIT_PAM │ Failed to set up PAM session. See PAMName= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│225 │ EXIT_NETWORK │ Failed to set up network namespacing. See │
│ │ │ PrivateNetwork= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│226 │ EXIT_NAMESPACE │ Failed to set up mount namespacing. See │
│ │ │ ReadOnlyPaths= and related settings above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│227 │ EXIT_NO_NEW_PRIVILEGES │ Failed to disable new privileges. See │
│ │ │ NoNewPrivileges=yes above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│228 │ EXIT_SECCOMP │ Failed to apply system call filters. See │
│ │ │ SystemCallFilter= and related settings │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│229 │ EXIT_SELINUX_CONTEXT │ Determining or changing SELinux context │
│ │ │ failed. See SELinuxContext= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│230 │ EXIT_PERSONALITY │ Failed to set up an execution domain │
│ │ │ (personality). See Personality= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│231 │ EXIT_APPARMOR_PROFILE │ Failed to prepare changing AppArmor │
│ │ │ profile. See AppArmorProfile= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│232 │ EXIT_ADDRESS_FAMILIES │ Failed to restrict address families. See │
│ │ │ RestrictAddressFamilies= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│233 │ EXIT_RUNTIME_DIRECTORY │ Setting up runtime directory failed. See │
│ │ │ RuntimeDirectory= and related settings │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│235 │ EXIT_CHOWN │ Failed to adjust socket ownership. Used for │
│ │ │ socket units only. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│236 │ EXIT_SMACK_PROCESS_LABEL │ Failed to set SMACK label. See │
│ │ │ SmackProcessLabel= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│237 │ EXIT_KEYRING │ Failed to set up kernel keyring. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│238 │ EXIT_STATE_DIRECTORY │ Failed to set up unit's state directory. │
│ │ │ See StateDirectory= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│239 │ EXIT_CACHE_DIRECTORY │ Failed to set up unit's cache directory. │
│ │ │ See CacheDirectory= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│240 │ EXIT_LOGS_DIRECTORY │ Failed to set up unit's logging directory. │
│ │ │ See LogsDirectory= above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│241 │ EXIT_CONFIGURATION_DIRECTORY │ Failed to set up unit's configuration │
│ │ │ directory. See ConfigurationDirectory= │
│ │ │ above. │
├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│242 │ EXIT_NUMA_POLICY │ Failed to set up unit's NUMA memory policy. │
│ │ │ See NUMAPolicy= and NUMAMask= above. │
└──────────┴──────────────────────────────┴─────────────────────────────────────────────┘
Finally, the BSD operating systems define a set of exit codes,
typically defined on Linux systems too:
Table 9. BSD exit codes
┌──────────┬────────────────┬─────────────────────┐
│Exit Code │ Symbolic Name │ Description │
├──────────┼────────────────┼─────────────────────┤
│64 │ EX_USAGE │ Command line usage │
│ │ │ error │
├──────────┼────────────────┼─────────────────────┤
│65 │ EX_DATAERR │ Data format error │
├──────────┼────────────────┼─────────────────────┤
│66 │ EX_NOINPUT │ Cannot open input │
├──────────┼────────────────┼─────────────────────┤
│67 │ EX_NOUSER │ Addressee unknown │
├──────────┼────────────────┼─────────────────────┤
│68 │ EX_NOHOST │ Host name unknown │
├──────────┼────────────────┼─────────────────────┤
│69 │ EX_UNAVAILABLE │ Service unavailable │
├──────────┼────────────────┼─────────────────────┤
│70 │ EX_SOFTWARE │ internal software │
│ │ │ error │
├──────────┼────────────────┼─────────────────────┤
│71 │ EX_OSERR │ System error (e.g., │
│ │ │ can't fork) │
├──────────┼────────────────┼─────────────────────┤
│72 │ EX_OSFILE │ Critical OS file │
│ │ │ missing │
├──────────┼────────────────┼─────────────────────┤
│73 │ EX_CANTCREAT │ Can't create (user) │
│ │ │ output file │
├──────────┼────────────────┼─────────────────────┤
│74 │ EX_IOERR │ Input/output error │
├──────────┼────────────────┼─────────────────────┤
│75 │ EX_TEMPFAIL │ Temporary failure; │
│ │ │ user is invited to │
│ │ │ retry │
├──────────┼────────────────┼─────────────────────┤
│76 │ EX_PROTOCOL │ Remote error in │
│ │ │ protocol │
├──────────┼────────────────┼─────────────────────┤
│77 │ EX_NOPERM │ Permission denied │
├──────────┼────────────────┼─────────────────────┤
│78 │ EX_CONFIG │ Configuration error │
└──────────┴────────────────┴─────────────────────┘
systemd(1), systemctl(1), systemd-analyze(1), journalctl(1),
systemd-system.conf(5), systemd.unit(5), systemd.service(5),
systemd.socket(5), systemd.swap(5), systemd.mount(5),
systemd.kill(5), systemd.resource-control(5), systemd.time(7),
systemd.directives(7), tmpfiles.d(5), exec(3)
1. Discoverable Partitions Specification
https://systemd.io/DISCOVERABLE_PARTITIONS
2. User/Group Name Syntax
https://systemd.io/USER_NAMES
3. No New Privileges Flag
https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html
4. proc.txt
https://www.kernel.org/doc/Documentation/filesystems/proc.txt
5. C escapes
https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences
6. most control characters
https://en.wikipedia.org/wiki/Control_character#In_ASCII
7. Base64
https://tools.ietf.org/html/rfc2045#section-6.8
8. LSB specification
https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/iniscrptact.html
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
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report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2020-08-13. (At that
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systemd 246 SYSTEMD.EXEC(5)
Pages that refer to this page: init(1) , systemctl(1) , systemd(1) , systemd-analyze(1) , systemd-id128(1) , systemd-run(1) , userdbctl(1) , sd_bus_creds_get_audit_login_uid(3) , sd_bus_creds_get_audit_session_id(3) , sd_bus_creds_get_cgroup(3) , sd_bus_creds_get_cmdline(3) , sd_bus_creds_get_comm(3) , sd_bus_creds_get_description(3) , sd_bus_creds_get_egid(3) , sd_bus_creds_get_euid(3) , sd_bus_creds_get_exe(3) , sd_bus_creds_get_fsgid(3) , sd_bus_creds_get_fsuid(3) , sd_bus_creds_get_gid(3) , sd_bus_creds_get_owner_uid(3) , sd_bus_creds_get_pid(3) , sd_bus_creds_get_ppid(3) , sd_bus_creds_get_selinux_context(3) , sd_bus_creds_get_session(3) , sd_bus_creds_get_sgid(3) , sd_bus_creds_get_slice(3) , sd_bus_creds_get_suid(3) , sd_bus_creds_get_supplementary_gids(3) , sd_bus_creds_get_tid(3) , sd_bus_creds_get_tid_comm(3) , sd_bus_creds_get_tty(3) , sd_bus_creds_get_uid(3) , sd_bus_creds_get_unique_name(3) , sd_bus_creds_get_unit(3) , sd_bus_creds_get_user_slice(3) , sd_bus_creds_get_user_unit(3) , sd_bus_creds_get_well_known_names(3) , sd_bus_creds_has_bounding_cap(3) , sd_bus_creds_has_effective_cap(3) , sd_bus_creds_has_inheritable_cap(3) , sd_bus_creds_has_permitted_cap(3) , sd_id128_get_boot(3) , sd_id128_get_boot_app_specific(3) , sd_id128_get_invocation(3) , sd_id128_get_machine(3) , sd_id128_get_machine_app_specific(3) , journald.conf(5) , journald@.conf(5) , journald.conf.d(5) , system.conf.d(5) , systemd.kill(5) , systemd.mount(5) , systemd.resource-control(5) , systemd.service(5) , systemd.socket(5) , systemd.swap(5) , systemd-system.conf(5) , systemd.unit(5) , systemd-user.conf(5) , systemd-user-runtime-dir(5) , tmpfiles.d(5) , user.conf.d(5) , user-runtime-dir.service(5) , user-runtime-dir@.service(5) , user.service(5) , user@.service(5) , 30-systemd-environment-d-generator(7) , daemon(7) , systemd.directives(7) , systemd.index(7) , systemd.journal-fields(7) , libnss_systemd.so.2(8) , nss-systemd(8) , systemd-coredump(8) , systemd-coredump.service(8) , systemd-coredump@.service(8) , systemd-coredump.socket(8) , systemd-journald(8) , systemd-journald-audit.socket(8) , systemd-journald-dev-log.socket(8) , systemd-journald.service(8) , systemd-journald@.service(8) , systemd-journald.socket(8) , systemd-journald@.socket(8) , systemd-journald-varlink.socket(8) , systemd-journald-varlink@.socket(8)