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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 ] [	-p project ] [ 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),  project  hierarchy  (P),	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.

       -p project
	      Set the file's project 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 have the	No_COW
       attribute set.)

       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  encryption  patches  to
       indicate	 that the file has been	encrypted.  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).

       A directory with	the 'P'	attribute  set	will  enforce  a  hierarchical
       structure  for  project id's.  This means that files and	directory cre-
       ated in the directory will inhert the  project  id  of  the  directory,
       rename  operations are constrained so when a file or directory is moved
       into another directory, that the	project	id's much match.  In addition,
       a  hard	link  to  file can only	be created when	the project id for the
       file and	the destination	directory match.

       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 1.43.4	 January 2017			     CHATTR(1)

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

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