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 +-=[acdeijstuACDST].

       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  `acdeijstuACDST'  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), no copy
       on write (C), 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.

       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.)

       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 '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 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 kernels.

       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)