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CHATTR(1)                                                            CHATTR(1)



NAME
       chattr - change file attributes on a Linux file system

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

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

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

       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  'acdeijstuADST'  select the new attributes for the files: append only
       (a), compressed (c), no dump (d), extent format  (e),  immutable  (i),  data  jour-
       nalling  (j),  secure  deletion (s), no tail-merging (t), undeletable (u), no atime
       updates (A), synchronous directory updates (D), synchronous updates (S), and top of
       directory hierarchy (T).

       The following attributes are read-only, and may be listed by lsattr(1) but not mod-
       ified by chattr: huge file (h), compression error (E), indexed directory (I),  com-
       pression raw access (X), and compressed dirty file (Z).

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.

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.  Note: please make  sure  to  read
       the bugs and limitations section at the end of this document.

       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 'e' attribute indicates that the file is using extents for mapping  the  blocks
       on disk.  It may not be removed using chattr(1).

       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).

       The 'h' attribute indicates the file is storing its blocks in units of the filesys-
       tem 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.

       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.  Note: please make sure to read the bugs and limitations sec-
       tion at the end of this document.

       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.  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 subdi-
       rectories closer together where possible.

       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.  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
       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 of the ext2 and ext3 filesystems.

       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.

SEE ALSO
       lsattr(1)



E2fsprogs version 1.41.12          May 2010                          CHATTR(1)

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