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 +-=[ASacdisu].
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 `ASacdijsu' select the new attributes for the
files: don't update atime (A), synchronous updates (S),
append only (a), compressed (c), no dump (d), immutable
(i), data journalling (j), secure deletion (s), and
undeletable (u).
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 pro
gram version.
-v version
Set the file's version/generation number.
ATTRIBUTES
When a file with the 'A' attribute set is modified, its
atime record is not modified. 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 can set or
clear this attribute.
A file with the `c' attribute set is automatically com
pressed 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.
A file with the `d' attribute set is not candidate for
backup when the dump(8) program is run.
A file with the `i' attribute cannot be modified: it can
not be deleted or renamed, no link can be created to this
superuser 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=journalled" option
all file data is already journalled and this attribute has
no effect.
When a file with the `s' attribute set is deleted, its
blocks are zeroed and written back to the disk.
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.
When a file with the `u' attribute set is deleted, its
contents are saved. This allows the user to ask for its
undeletion.
AUTHOR
chattr was written by Remy Card <Remy.Card@linux.org>.
BUGS AND LIMITATIONS
As of Linux 2.2, the `c', 's', and `u' attribute are not
honored by the kernel filesystem code. These attributes
will be implemented in a future ext2 fs version.
The `j' option is only useful if the filesystem is mounted
as ext3.
AVAILABILITY
chattr is part of the e2fsprogs package and is available
from http://e2fsprogs.sourceforge.net.
SEE ALSO
lsattr(1)
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