noble (1) chattr.1.gz

Provided by: e2fsprogs_1.47.0-2.4~exp1ubuntu4.1_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).