Provided by: e2fsprogs_1.47.1-1ubuntu1_amd64 bug

NAME

       chattr - change file attributes on a Linux file system

SYNOPSIS

       chattr [ -RVf ] [ -v version ] [ -p project ] [ mode ] files...

DESCRIPTION

       chattr changes the file attributes on a Linux file system.

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

       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 'aAcCdDeFijmPsStTux' 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),  case-insensitive  directory  lookups  (F),
       immutable (i), data journaling (j), don't compress  (m),  project  hierarchy  (P),  secure
       deletion  (s),  synchronous  updates  (S), no tail-merging (t), top of directory hierarchy
       (T), undeletable (u), and direct access for files (x).

       The following attributes are read-only, and may be listed by lsattr(1) but not modified by
       chattr: encrypted (E), indexed directory (I), inline data (N), and verity (V).

       Not all flags are supported or utilized by all file systems; refer to file system-specific
       man pages such as btrfs(5), ext4(5),  mkfs.f2fs(8),  and  xfs(5)  for  more  file  system-
       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.

       -p project
              Set the file's project number.

ATTRIBUTES

       a      A  file  with  the 'a' attribute set can only be opened in append mode for writing.
              Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE  capability  can
              set or clear this attribute.

       A      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.

       c      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.  (Note: For btrfs, If
              the 'c' flag is set, then the 'C' flag cannot be set.  Also  conflicts  with  btrfs
              mount option 'nodatasum')

       C      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  have  the
              No_COW attribute set. If the 'C' flag is set, then the 'c' flag cannot be set.)

       d      A  file  with  the 'd' attribute set is not a candidate for backup when the dump(8)
              program is run.

       D      When a directory with the 'D' attribute set is modified, the  changes  are  written
              synchronously to the disk; this is equivalent to the 'dirsync' mount option applied
              to a subset of the files.

       e      The 'e' attribute indicates that the file is using extents for mapping  the  blocks
              on disk.  It may not be removed using chattr(1).

       E      A  file,  directory, or symlink with the 'E' attribute set is encrypted by the file
              system.  This attribute may not be set or cleared using chattr(1), although it  can
              be displayed by lsattr(1).

       F      A  directory  with the 'F' attribute set indicates that all the path lookups inside
              that directory are made in a case-insensitive fashion.  This attribute can only  be
              changed in empty directories on file systems with the casefold feature enabled.

       i      A  file with the 'i' attribute cannot be modified: it cannot be deleted or renamed,
              no link can be created to this file,  most  of  the  file's  metadata  can  not  be
              modified,  and  the  file can not be opened in write mode.  Only the superuser or a
              process possessing  the  CAP_LINUX_IMMUTABLE  capability  can  set  or  clear  this
              attribute.

       I      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 cleared using chattr(1), although
              it can be displayed by lsattr(1).

       j      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 file system is mounted with
              the  "data=ordered"  or "data=writeback" options and the file system has a journal.
              When the file system 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.

       m      A file with the 'm' attribute is excluded from compression  on  file  systems  that
              support per-file compression.

       N      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 cleared using chattr(1), although  it
              can be displayed by lsattr(1).

       P      A  directory  with  the 'P' attribute set will enforce a hierarchical structure for
              project id's.  This means that files and directories created in the directory  will
              inherit  the project id of the directory, rename operations are constrained so when
              a file or directory is moved into another directory,  that  the  project  ids  must
              match.   In  addition,  a hard link to file can only be created when the project id
              for the file and the destination directory match.

       s      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.

       S      When a file with the 'S'  attribute  set  is  modified,  the  changes  are  written
              synchronously to the disk; this is equivalent to the 'sync' mount option applied to
              a subset of the files.

       t      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 file systems which support tail-
              merging).  This is necessary for applications such as  LILO  which  read  the  file
              system  directly,  and  which don't understand tail-merged files.  Note: As of this
              writing, the ext2, ext3, and ext4 file systems do not support tail-merging.

       T      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.

       u      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.

       x      A  file  with  the  'x' requests the use of direct access (dax) mode, if the kernel
              supports DAX.  This can be overridden by the 'dax=never' mount  option.   For  more
              information       see       the       kernel       documentation      for      dax:
              <https://www.kernel.org/doc/html/latest/filesystems/dax.html>.

              If the attribute is set on an existing directory, it will be inherited by all files
              and  subdirectories that are subsequently created in the directory.  If an existing
              directory has contained some files and subdirectories, modifying the  attribute  on
              the   parent   directory   doesn't   change  the  attributes  on  these  files  and
              subdirectories.

       V      A file with the 'V' attribute set has fs-verity enabled.  It cannot be written  to,
              and  the  file  system  will  automatically  verify all data read from it against a
              cryptographic hash that covers the entire file's contents, e.g. via a Merkle  tree.
              This  makes  it  possible to efficiently authenticate the file.  This attribute may
              not be set or cleared 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 file systems
       as implemented in the current mainline Linux kernels.  Setting 'a' and 'i' attributes will
       not affect the ability to write to already existing file descriptors.

       The 'j' option is only useful for ext3 and ext4 file systems.

       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), mkfs.f2fs(8), xfs(5).