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 +-=[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  alloca-
       tor 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  under-
       stand  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 and ext3 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 1.42.5					     July 2012								 CHATTR(1)