|
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 +-=[aAcCdDeijsStTu].
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 'aAcCdDeijsStTu' 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), 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: compression error (E), huge
file (h), indexed directory (I), inline data (N), compression raw
access (X), and compressed dirty file (Z).
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 file with the 'a' attribute set can only be open in append mode for
writing. Only the superuser or a process possessing the
CAP_LINUX_IMMUTABLE capability can set or clear this attribute.
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.
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.
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.)
A file with the 'd' attribute set is not candidate for backup when
the dump(8) program is run.
When a directory with the 'D' attribute set is modified, the changes
are written synchronously on the disk; this is equivalent to the
'dirsync' mount option applied to a subset of the files.
The 'e' attribute indicates that the file is using extents for
mapping the blocks on disk. It may not be removed using chattr(1).
The 'E' attribute is used by the experimental encryption patches to
indicate that the file has been encrypted. It may not be set or
reset using chattr(1), although it can be displayed by lsattr(1).
The 'h' attribute indicates the file is storing its blocks in units
of the filesystem blocksize instead of in units of sectors, and means
that the file is (or at one time was) larger than 2TB. It may not be
set or reset using chattr(1), although it can be displayed by
lsattr(1).
A file with the 'i' attribute cannot be modified: it cannot be
deleted or renamed, no link can be created to this file and no data
can be written to the file. Only the superuser or a process
possessing the CAP_LINUX_IMMUTABLE capability can set or clear this
attribute.
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
reset using chattr(1), although it can be displayed by lsattr(1).
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
filesystem is mounted with the "data=ordered" or "data=writeback"
options. 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.
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 reset
using chattr(1), although it can be displayed by lsattr(1).
A directory with the 'P' attribute set will enforce a hierarchical
structure for project id's. This means that files and directory
created in the directory will inhert the project id of the directory,
rename operations are constrained so when a file or directory is
moved into another directory, that the project id's much match. In
addition, a hard link to file can only be created when the project id
for the file and the destination directory match.
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.
When a file with the 'S' attribute set is modified, the changes are
written synchronously on the disk; this is equivalent to the 'sync'
mount option applied to a subset of the files.
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 or
ext3 filesystems do not (yet, except in very experimental patches)
support tail-merging.
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.
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.
The 'X' attribute is used by the experimental compression patches to
indicate that the raw contents of a compressed file can be accessed
directly. It currently may not be set or reset using chattr(1),
although it can be displayed by lsattr(1).
The 'Z' attribute is used by the experimental compression patches to
indicate a compressed file is dirty. It may not be set or reset
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.
The 'j' option is only useful if the filesystem is mounted as ext3 or
ext4.
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 2017-07-05.
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
E2fsprogs version 1.43.5-WIP February 2017 CHATTR(1)
Pages that refer to this page: chattr(1), lsattr(1), fallocate(2), ioctl_iflags(2), mount(2), statx(2), utime(2), utimensat(2), ext4(5), tmpfiles.d(5), xfs(5), btrfs-property(8), xfsdump(8)