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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | MODULE TYPES PROVIDED | ENVIRONMENT | SESSION LIMITS | EXAMPLE | SEE ALSO | NOTES | COLOPHON |
PAM_SYSTEMD(8) pam_systemd PAM_SYSTEMD(8)
pam_systemd - Register user sessions in the systemd login manager
pam_systemd.so
pam_systemd registers user sessions with the systemd login manager
systemd-logind.service(8), and hence the systemd control group
hierarchy.
The module also applies various resource management and runtime
parameters to the new session, as configured in the JSON User
Record[1] of the user, when one is defined.
On login, this module — in conjunction with systemd-logind.service —
ensures the following:
1. If it does not exist yet, the user runtime directory
/run/user/$UID is either created or mounted as new "tmpfs" file
system with quota applied, and its ownership changed to the user
that is logging in.
2. The $XDG_SESSION_ID environment variable is initialized. If
auditing is available and pam_loginuid.so was run before this
module (which is highly recommended), the variable is initialized
from the auditing session id (/proc/self/sessionid). Otherwise,
an independent session counter is used.
3. A new systemd scope unit is created for the session. If this is
the first concurrent session of the user, an implicit per-user
slice unit below user.slice is automatically created and the
scope placed into it. An instance of the system service
user@.service, which runs the systemd user manager instance, is
started.
4. The "$TZ", "$EMAIL" and "$LANG" environment variables are
configured for the user, based on the respective data from the
user's JSON record (if it is defined). Moreover, any environment
variables explicitly configured in the user record are imported,
and the umask, nice level, and resource limits initialized.
On logout, this module ensures the following:
1. If enabled in logind.conf(5) (KillUserProcesses=), all processes
of the session are terminated. If the last concurrent session of
a user ends, the user's systemd instance will be terminated too,
and so will the user's slice unit.
2. If the last concurrent session of a user ends, the user runtime
directory /run/user/$UID and all its contents are removed, too.
If the system was not booted up with systemd as init system, this
module does nothing and immediately returns PAM_SUCCESS.
The following options are understood:
class=
Takes a string argument which sets the session class. The
XDG_SESSION_CLASS environment variable (see below) takes
precedence. One of "user", "greeter", "lock-screen" or
"background". See sd_session_get_class(3) for details about the
session class.
type=
Takes a string argument which sets the session type. The
XDG_SESSION_TYPE environment variable (see below) takes
precedence. One of "unspecified", "tty", "x11", "wayland" or
"mir". See sd_session_get_type(3) for details about the session
type.
desktop=
Takes a single, short identifier string for the desktop
environment. The XDG_SESSION_DESKTOP environment variable (see
below) takes precedence. This may be used to indicate the session
desktop used, where this applies and if this information is
available. For example: "GNOME", or "KDE". It is recommended to
use the same identifiers and capitalization as for
$XDG_CURRENT_DESKTOP, as defined by the Desktop Entry
Specification[2]. (However, note that the option only takes a
single item, and not a colon-separated list like
$XDG_CURRENT_DESKTOP.) See sd_session_get_desktop(3) for further
details.
debug[=]
Takes an optional boolean argument. If yes or without the
argument, the module will log debugging information as it
operates.
Only session is provided.
The following environment variables are initialized by the module and
available to the processes of the user's session:
$XDG_SESSION_ID
A short session identifier, suitable to be used in filenames. The
string itself should be considered opaque, although often it is
just the audit session ID as reported by /proc/self/sessionid.
Each ID will be assigned only once during machine uptime. It may
hence be used to uniquely label files or other resources of this
session. Combine this ID with the boot identifier, as returned by
sd_id128_get_boot(3), for a globally unique identifier.
$XDG_RUNTIME_DIR
Path to a user-private user-writable directory that is bound to
the user login time on the machine. It is automatically created
the first time a user logs in and removed on the user's final
logout. If a user logs in twice at the same time, both sessions
will see the same $XDG_RUNTIME_DIR and the same contents. If a
user logs in once, then logs out again, and logs in again, the
directory contents will have been lost in between, but
applications should not rely on this behavior and must be able to
deal with stale files. To store session-private data in this
directory, the user should include the value of $XDG_SESSION_ID
in the filename. This directory shall be used for runtime file
system objects such as AF_UNIX sockets, FIFOs, PID files and
similar. It is guaranteed that this directory is local and offers
the greatest possible file system feature set the operating
system provides. For further details, see the XDG Base Directory
Specification[3]. $XDG_RUNTIME_DIR is not set if the current
user is not the original user of the session.
$TZ, $EMAIL, $LANG
If a JSON user record is known for the user logging in these
variables are initialized from the respective data in the record.
The following environment variables are read by the module and may be
used by the PAM service to pass metadata to the module. If these
variables are not set when the PAM module is invoked but can be
determined otherwise they are set by the module, so that these
variables are initialized for the session and applications if known
at all.
$XDG_SESSION_TYPE
The session type. This may be used instead of type= on the module
parameter line, and is usually preferred.
$XDG_SESSION_CLASS
The session class. This may be used instead of class= on the
module parameter line, and is usually preferred.
$XDG_SESSION_DESKTOP
The desktop identifier. This may be used instead of desktop= on
the module parameter line, and is usually preferred.
$XDG_SEAT
The seat name the session shall be registered for, if any.
$XDG_VTNR
The VT number the session shall be registered for, if any. (Only
applies to seats with a VT available, such as "seat0")
If not set, pam_systemd will initialize $XDG_SEAT and $XDG_VTNR based
on the $DISPLAY variable (if the latter is set).
PAM modules earlier in the stack, that is those that come before
pam_systemd.so, can set session scope limits using the PAM context
objects. The data for these objects is provided as NUL-terminated C
strings and maps directly to the respective unit resource control
directives. Note that these limits apply to individual sessions of
the user, they do not apply to all user processes as a combined
whole. In particular, the per-user user@.service unit instance, which
runs the systemd --user manager process and its children, and is
tracked outside of any session, being shared by all the user's
sessions, is not covered by these limits.
See systemd.resource-control(5) for more information about the
resources. Also, see pam_set_data(3) for additional information about
how to set the context objects.
systemd.memory_max=
Sets unit MemoryMax=.
systemd.tasks_max=
Sets unit TasksMax=.
systemd.cpu_weight=
Sets unit CPUWeight=.
systemd.io_weight=
Sets unit IOWeight=.
systemd.runtime_max_sec=
Sets unit RuntimeMaxSec=.
Example data as can be provided from an another PAM module:
pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
pam_set_data(handle, "systemd.tasks_max", (void *)"50", cleanup);
pam_set_data(handle, "systemd.cpu_weight", (void *)"100", cleanup);
pam_set_data(handle, "systemd.io_weight", (void *)"340", cleanup);
pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);
Here's an example PAM configuration fragment that allows users
sessions to be managed by systemd-logind.service:
#%PAM-1.0
auth sufficient pam_unix.so
-auth sufficient pam_systemd_home.so
auth required pam_deny.so
account required pam_nologin.so
-account sufficient pam_systemd_home.so
account sufficient pam_unix.so
account required pam_permit.so
-password sufficient pam_systemd_home.so
password sufficient pam_unix.so sha512 shadow try_first_pass try_authtok
password required pam_deny.so
-session optional pam_keyinit.so revoke
-session optional pam_loginuid.so
-session optional pam_systemd_home.so
-session optional pam_systemd.so
session required pam_unix.so
systemd(1), systemd-logind.service(8), logind.conf(5), loginctl(1),
pam_systemd_home(8), pam.conf(5), pam.d(5), pam(8), pam_loginuid(8),
systemd.scope(5), systemd.slice(5), systemd.service(5)
1. JSON User Record
https://systemd.io/USER_RECORD
2. Desktop Entry Specification
http://standards.freedesktop.org/desktop-entry-spec/latest/
3. XDG Base Directory Specification
http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
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
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-11.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
systemd 246 PAM_SYSTEMD(8)
Pages that refer to this page: org.freedesktop.login1(5) , systemd.exec(5) , systemd-user-runtime-dir(5) , user-runtime-dir.service(5) , user-runtime-dir@.service(5) , user.service(5) , user@.service(5) , 30-systemd-environment-d-generator(7) , systemd.directives(7) , systemd.index(7) , pam_systemd_home(8) , systemd-logind(8) , systemd-logind.service(8)