CHATTR(1) General Commands Manual CHATTR(1)
NAME
chattr - change file attributes on a Linux file system
SYNOPSIS
chattr [ -RVf ] [ -v version ] [ -p project ] [ mode ] files...
DESCRIPTION
chattr changes the file attributes on a Linux file system.
The format of a symbolic mode is +-=[aAcCdDeFijmPsStTux].
The operator '+' causes the selected attributes to be added to the ex-
isting attributes of the files; '-' causes them to be removed; and '='
causes them to be the only attributes that the files have.
The letters 'aAcCdDeFijmPsStTux' 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 jour-
naling (j), don't compress (m), project hierarchy (P), secure deletion
(s), synchronous updates (S), no tail-merging (t), top of directory hi-
erarchy (T), undeletable (u), and direct access for files (x).
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 file systems; refer to
file system-specific man pages such as btrfs(5), ext4(5), mkfs.f2fs(8),
and xfs(5) for more file system-specific details.
OPTIONS
-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.
ATTRIBUTES
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 uncom-
pressed data. A write to this file compresses data before stor-
ing them on the disk. Note: please make sure to read the bugs
and limitations section at the end of this document. (Note: For
btrfs, If the 'c' flag is set, then the 'C' flag cannot be set.
Also conflicts with btrfs mount option 'nodatasum')
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 direc-
tory, it will have no effect on the directory, but new files cre-
ated in that directory will have the No_COW attribute set. If the
'C' flag is set, then the 'c' flag cannot be 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 en-
crypted by the file system. 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 at-
tribute.
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 file system 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.
m A file with the 'm' attribute is excluded from compression on
file systems that support per-file compression.
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 hierarchi-
cal structure for project id's. This means that files and direc-
tories 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 di-
rectory 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 docu-
ment.
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 frag-
ment at the end of the file merged with other files (for those
file systems which support tail-merging). This is necessary for
applications such as LILO which read the file system directly,
and which don't understand tail-merged files. Note: As of this
writing, the ext2, ext3, and ext4 file systems 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 al-
locator. This is a hint to the block allocator used by ext3 and
ext4 that the subdirectories under this directory are not re-
lated, 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 subdirec-
tories 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.
x A file with the 'x' requests the use of direct access (dax) mode,
if the kernel supports DAX. This can be overridden by the
'dax=never' mount option. For more information see the kernel
documentation for dax: <https://www.kernel.org/doc/html/lat-
est/filesystems/dax.html>.
If the attribute is set on an existing directory, it will be in-
herited by all files and subdirectories that are subsequently
created in the directory. If an existing directory has contained
some files and subdirectories, modifying the attribute on the
parent directory doesn't change the attributes on these files and
subdirectories.
V A file with the 'V' attribute set has fs-verity enabled. It can-
not be written to, and the file system 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).
AUTHOR
chattr was written by Remy Card <Remy.Card@linux.org>. It is currently
being maintained by Theodore Ts'o <tytso@alum.mit.edu>.
BUGS AND LIMITATIONS
The 'c', 's', and 'u' attributes are not honored by the ext2, ext3, and
ext4 file systems 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.
AVAILABILITY
chattr is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
SEE ALSO
lsattr(1), btrfs(5), ext4(5), mkfs.f2fs(8), xfs(5).
E2fsprogs version 1.47.2 January 2025 CHATTR(1)
Generated by dwww version 1.16 on Tue Dec 16 04:44:09 CET 2025.