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 +-=[ASacDdistu].
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 `ASacDdijsu' select the new attributes for the
files: don't update atime (A), synchronous updates (S),
synchronous directory updates (D), append only (a), com
pressed (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 accessed, 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.
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 sub
set of the files.
A file with the `d' attribute set is not candidate for
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.
A file with the 't' attribute will not have a partial
block fragment at the 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 who don't understand tail-merged
files.
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@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.
The `D' option is only useful on Linux kernel 2.5.19 and
later.
AVAILABILITY
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