CHATTR linux command manual

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  directory  updates  (D),  syn-
       chronous updates (S), and top of directory hierarchy (T).

OPTIONS
       -R     Recursively  change  attributes  of  directories and their con-
              tents.  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 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   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) program 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 direc-
       tory 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  supe-
       ruser  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 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  directory  with  the  'T' attribute will be deemed to be the top of
       directory hierarchies 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-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.

       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 .  It is cur-
       rently being maintained by Theodore Ts'o .

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.

SEE ALSO
       lsattr(1)



E2fsprogs version 1.35          February 2004                       CHATTR(1)