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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ATTRIBUTES | AUTHOR | BUGS AND LIMITATIONS | AVAILABILITY | SEE ALSO | COLOPHON |
CHATTR(1) General Commands Manual CHATTR(1)
chattr - change file attributes on a Linux file system
chattr [ -RVf ] [ -v version ] [ -p project ] [ mode ] files...
chattr changes the file attributes on a Linux file system.
The format of a symbolic mode is +-=[aAcCdDeFijPsStTu].
The operator '+' causes the selected attributes to be added to the
existing attributes of the files; '-' causes them to be removed; and
'=' causes them to be the only attributes that the files have.
The letters 'aAcCdDeFijPsStTu' select the new attributes for the
files: append only (a), no atime updates (A), compressed (c), no copy
on write (C), no dump (d), synchronous directory updates (D), extent
format (e), case-insensitive directory lookups (F), immutable (i),
data journalling (j), project hierarchy (P), secure deletion (s),
synchronous updates (S), no tail-merging (t), top of directory
hierarchy (T), and undeletable (u).
The following attributes are read-only, and may be listed by
lsattr(1) but not modified by chattr: encrypted (E), indexed
directory (I), inline data (N), and verity (V).
Not all flags are supported or utilized by all filesystems; refer to
filesystem-specific man pages such as btrfs(5), ext4(5), and xfs(5)
for more filesystem-specific details.
-R Recursively change attributes of directories and their
contents.
-V Be verbose with chattr's output and print the program version.
-f Suppress most error messages.
-v version
Set the file's version/generation number.
-p project
Set the file's project number.
a A file with the 'a' attribute set can only be opened in append
mode for writing. Only the superuser or a process possessing
the CAP_LINUX_IMMUTABLE capability can set or clear this
attribute.
A When a file with the 'A' attribute set is accessed, its atime
record is not modified. This avoids a certain amount of disk
I/O for laptop systems.
c A file with the 'c' attribute set is automatically compressed
on the disk by the kernel. A read from this file returns
uncompressed data. A write to this file compresses data
before storing them on the disk. Note: please make sure to
read the bugs and limitations section at the end of this
document.
C A file with the 'C' attribute set will not be subject to copy-
on-write updates. This flag is only supported on file systems
which perform copy-on-write. (Note: For btrfs, the 'C' flag
should be set on new or empty files. If it is set on a file
which already has data blocks, it is undefined when the blocks
assigned to the file will be fully stable. If the 'C' flag is
set on a directory, it will have no effect on the directory,
but new files created in that directory will have the No_COW
attribute set.)
d A file with the 'd' attribute set is not a candidate for
backup when the dump(8) program is run.
D When a directory with the 'D' attribute set is modified, the
changes are written synchronously to the disk; this is
equivalent to the 'dirsync' mount option applied to a subset
of the files.
e The 'e' attribute indicates that the file is using extents for
mapping the blocks on disk. It may not be removed using
chattr(1).
E A file, directory, or symlink with the 'E' attribute set is
encrypted by the filesystem. This attribute may not be set or
cleared using chattr(1), although it can be displayed by
lsattr(1).
F A directory with the 'F' attribute set indicates that all the
path lookups inside that directory are made in a case-
insensitive fashion. This attribute can only be changed in
empty directories on file systems with the casefold feature
enabled.
i A file with the 'i' attribute cannot be modified: it cannot be
deleted or renamed, no link can be created to this file, most
of the file's metadata can not be modified, and the file can
not be opened in write mode. Only the superuser or a process
possessing the CAP_LINUX_IMMUTABLE capability can set or clear
this attribute.
I The 'I' attribute is used by the htree code to indicate that a
directory is being indexed using hashed trees. It may not be
set or cleared using chattr(1), although it can be displayed
by lsattr(1).
j A file with the 'j' attribute has all of its data written to
the ext3 or ext4 journal before being written to the file
itself, if the file system is mounted with the "data=ordered"
or "data=writeback" options and the file system has a journal.
When the filesystem is mounted with the "data=journal" option
all file data is already journalled and this attribute has no
effect. Only the superuser or a process possessing the
CAP_SYS_RESOURCE capability can set or clear this attribute.
N A file with the 'N' attribute set indicates that the file has
data stored inline, within the inode itself. It may not be set
or cleared using chattr(1), although it can be displayed by
lsattr(1).
P A directory with the 'P' attribute set will enforce a
hierarchical structure for project id's. This means that
files and directories created in the directory will inherit
the project id of the directory, rename operations are
constrained so when a file or directory is moved into another
directory, that the project ids must match. In addition, a
hard link to file can only be created when the project id for
the file and the destination directory match.
s When a file with the 's' attribute set is deleted, its blocks
are zeroed and written back to the disk. Note: please make
sure to read the bugs and limitations section at the end of
this document.
S When a file with the 'S' attribute set is modified, the
changes are written synchronously to the disk; this is
equivalent to the 'sync' mount option applied to a subset of
the files.
t A file with the 't' attribute will not have a partial block
fragment at the end of the file merged with other files (for
those filesystems which support tail-merging). This is
necessary for applications such as LILO which read the
filesystem directly, and which don't understand tail-merged
files. Note: As of this writing, the ext2, ext3, and ext4
filesystems do not support tail-merging.
T A directory with the 'T' attribute will be deemed to be the
top of directory hierarchies for the purposes of the Orlov
block allocator. This is a hint to the block allocator used
by ext3 and ext4 that the subdirectories under this directory
are not related, and thus should be spread apart for
allocation purposes. For example it is a very good idea to
set the 'T' attribute on the /home directory, so that
/home/john and /home/mary are placed into separate block
groups. For directories where this attribute is not set, the
Orlov block allocator will try to group subdirectories closer
together where possible.
u When a file with the 'u' attribute set is deleted, its
contents are saved. This allows the user to ask for its
undeletion. Note: please make sure to read the bugs and
limitations section at the end of this document.
V A file with the 'V' attribute set has fs-verity enabled. It
cannot be written to, and the filesystem will automatically
verify all data read from it against a cryptographic hash that
covers the entire file's contents, e.g. via a Merkle tree.
This makes it possible to efficiently authenticate the file.
This attribute may not be set or cleared using chattr(1),
although it can be displayed by lsattr(1).
chattr was written by Remy Card <Remy.Card@linux.org>. It is
currently being maintained by Theodore Ts'o <tytso@alum.mit.edu>.
The 'c', 's', and 'u' attributes are not honored by the ext2, ext3,
and ext4 filesystems as implemented in the current mainline Linux
kernels. Setting 'a' and 'i' attributes will not affect the ability
to write to already existing file descriptors.
The 'j' option is only useful for ext3 and ext4 file systems.
The 'D' option is only useful on Linux kernel 2.5.19 and later.
chattr is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
lsattr(1), btrfs(5), ext4(5), xfs(5).
This page is part of the e2fsprogs (utilities for ext2/3/4
filesystems) project. Information about the project can be found at
⟨http://e2fsprogs.sourceforge.net/⟩. It is not known how to report
bugs for this man page; if you know, please send a mail to
man-pages@man7.org. This page was obtained from the project's
upstream Git repository
⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on 2020-08-13.
(At that time, the date of the most recent commit that was found in
the repository was 2020-03-21.) If you discover any rendering prob‐
lems in this HTML version of the page, or you believe there is a bet‐
ter 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
E2fsprogs version 1.46-WIP March 2020 CHATTR(1)
Pages that refer to this page: chattr(1) , lsattr(1) , rm(1) , fallocate(2) , ioctl_iflags(2) , mount(2) , statx(2) , utime(2) , utimensat(2) , utimes(2) , futimens(3) , ext2(5) , ext3(5) , ext4(5) , tmpfiles.d(5) , xfs(5) , btrfs-property(8) , xfsdump(8)