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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  journalling  (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 modified by chattr: huge file
       (h), compression error (E), indexed directory (I), compression 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 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.  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) program is run.

       The 'E' attribute is used by the experimental compression patches to indicate that a compressed file has a com-
       pression 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 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.

       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 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  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.

       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.  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  com-
       pressed  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.CardATlinux.org>.  It is currently being maintained by Theodore Ts'o
       <tytsoATalum.edu>.

BUGS AND LIMITATIONS
       The 'c', 's',  and 'u' attributes are not honored by the ext2 and ext3 filesystems as implemented in  the  cur-
       rent  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)