chattr



CHATTR(1)                                                            CHATTR(1)




NAME

       chattr - change file attributes on a Linux second extended file system


SYNOPSIS

       chattr [ -RV ] [ -v version ] [ mode ] files...


DESCRIPTION

       chattr changes the file attributes on a Linux second extended file sys-
       tem.

       The format of a symbolic mode is +-=[ASacDdIijsTtu].

       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 ‘acdijsuADST’ select the  new  attributes  for  the  files:
       append only (a), compressed (c), no dump (d), immutable (i), data jour-
       nalling (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).


OPTIONS

       -R     Recursively change attributes of directories and their contents.
              Symbolic links encountered during recursive directory traversals
              are ignored.

       -V     Be verbose with chattr’s output and print the program version.

       -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 sys-
       tems.

       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.

       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 ’I’ attribute is used by the htree code to indicate that  a  direc-
       tory  is behind 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 ‘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 supe-
       ruser 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.

       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
       (which is used in on systems with Linux 2.5.46 or later).

       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 filesys-
       tems  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.

       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.
       These attributes may be implemented in future versions ext2 and ext3.

       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 1.38             June 2005                         CHATTR(1)

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