chattr - phpMan

CHATTR(1) CHATTR(1)

NAME
chattr - change file attributes on a Linux second extended file system

SYNOPSIS
chattr [ -RV ] [ -v version ] [ mode ] files...

DESCRIPTION
chattr changes the file attributes on a Linux second extended file system.

The format of a symbolic mode is +-=[ASacDdIijsTtu].

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 ‘acdijsuADST’ select the new attributes for the files: append only (a),
compressed (c), no dump (d), immutable (i), data journalling (j), secure deletion
(s), no tail-merging (t), undeletable (u), no atime updates (A), synchronous direc-
tory updates (D), synchronous updates (S), and top of directory hierarchy (T).

OPTIONS
-R Recursively change attributes of directories and their contents. Symbolic
links encountered during recursive directory traversals are ignored.

-V Be verbose with chattr’s output and print the program version.

-v version
Set the file’s version/generation number.

ATTRIBUTES
When a file with the ’A’ attribute set is accessed, its atime record is not modi-
fied. This avoids a certain amount of disk I/O for laptop systems.

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.

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.

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.

A file with the ‘d’ attribute set is not candidate for backup when the dump(8) pro-
gram is run.

The ’E’ attribute is used by the experimental compression patches to indicate that
a compressed file has a compression error. It may not be set or reset using
chattr(1), although it can be displayed by lsattr(1).

The ’I’ attribute is used by the htree code to indicate that a directory is behind
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 ‘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.

A file with the ‘j’ attribute has all of its data written to the ext3 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.

When a file with the ‘s’ attribute set is deleted, its blocks are zeroed and writ-
ten back to the disk.

When a file with the ‘S’ attribute set is modified, the changes are written syn-
chronously on the disk; this is equivalent to the ‘sync’ mount option applied to a
subset of the files.

A directory with the ’T’ attribute will be deemed to be the top of directory hier-
archies for the purposes of the Orlov block allocator (which is used in on systems
with Linux 2.5.46 or later).

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-merg-
ing). 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) sup-
port tail-merging.

When a file with the ‘u’ attribute set is deleted, its contents are saved. This
allows the user to ask for its undeletion.

The ’X’ attribute is used by the experimental compression patches to indicate that
a 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).

AUTHOR
chattr was written by Remy Card <Remy.Card AT linux.org>. It is currently being main-
tained by Theodore Ts’o <tytso AT alum.edu>.

BUGS AND LIMITATIONS
The ‘c’, ’s’, and ‘u’ attributes are not honored by the ext2 and ext3 filesystems
as implemented in the current mainline Linux kernels. These attributes may be
implemented in future versions ext2 and ext3.

The ‘j’ option is only useful if the filesystem is mounted as ext3.

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.