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)

E2fsprogs version 1.42.9                          February 2014                                        CHATTR(1)