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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 ex-
       isting 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), in-
       dexed 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_IM-
       MUTABLE 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 at-
       tribute.)

       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" op-
       tions.  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  us-
       ing chattr(1), although it can be displayed by lsattr(1).

       When  a	file with the 's' attribute set	is deleted, its	blocks are ze-
       roed 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 di-
       rectory 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 di-
       rectly.	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)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ATTRIBUTES | AUTHOR | BUGS AND LIMITATIONS | AVAILABILITY | SEE ALSO

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