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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 +-=[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), 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.

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 systems.

       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.)

       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 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 '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 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).

       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 capability 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).

       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 filesystems 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 kernels.

       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).