CHATTR(1)                                 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 +-=[acdeijstuADST].        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  ‘acdeijstuADST’  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-merg-        ing (t), undeletable (u), no atime updates (A),    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 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.        Note:  please make sure to read the bugs and limitations section at the        end of this document.        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 direc-        tory 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 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.  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 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.     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.        These attributes may be implemented in future versions of the ext2  and        ext3 filesystems.        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 1.41.12       May 2010                 CHATTR(1)