CHATTR(1)                   General Commands Manual                  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 +-=[aAcCdDeijsStTu].

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

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

       Not  all  flags  are supported or utilized by all filesystems; refer to
       filesystem-specific man pages such as btrfs(5), ext4(5), and xfs(5) for
       more filesystem-specific details.

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
       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.

       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 sys-
       tems.

       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.

       A  file with the 'C' attribute set will not be subject to copy-on-write
       updates.  This flag is only supported on  file  systems  which  perform
       copy-on-write.   (Note: For btrfs, the 'C' flag should be set on new or
       empty files.  If it is set on a file which already has data blocks,  it
       is undefined when the blocks assigned to the file will be fully stable.
       If the 'C' flag is set on a directory, it will have no  effect  on  the
       directory,  but  new  files  created  in that directory will the No_COW
       attribute.)

       A file with the 'd' attribute set is not candidate for backup when  the
       dump(8) program is run.

       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.

       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 '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  'h' attribute indicates the file is storing its blocks in units of
       the filesystem 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.

       The  'I'  attribute is used by the htree code to indicate that a direc-
       tory is being 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 'j' attribute has all of its data written to the ext3
       or ext4 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  capa-
       bility can set or clear this attribute.

       A  file  with  the  'N'  attribute set indicates that the file has data
       stored inline, within the inode itself. It may  not  be  set  or  reset
       using chattr(1), although it can be displayed by lsattr(1).

       When  a  file  with  the  's'  attribute set is deleted, its blocks are
       zeroed and written back to the disk.  Note: please make  sure  to  read
       the bugs and limitations section at the end of this document.

       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 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 filesys-
       tems do not (yet, except in very experimental  patches)  support  tail-
       merging.

       A  directory  with  the  'T'  attribute will be deemed to be the top of
       directory hierarchies 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 subdirectories closer together where possible.

       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  the  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>.  It is currently
       being maintained by Theodore Ts'o <tytso@alum.mit.edu>.

BUGS AND LIMITATIONS
       The 'c', 's',  and 'u' attributes are not honored by  the  ext2,  ext3,
       and  ext4 filesystems as implemented in the current mainline Linux ker-
       nels.

       The 'j' option is only useful if the filesystem is mounted as  ext3  or
       ext4.

       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), btrfs(5), ext4(5), xfs(5).



E2fsprogs version 1.42.12         August 2014                        CHATTR(1)
