bionic (1) chattr.1.gz

Provided by: e2fsprogs_1.44.1-1ubuntu1.4_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 +-=[aAcCdDeijPsStTu].

       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 'aAcCdDeijPsStTu' 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), project hierarchy (P), 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:
       encrypted (E), indexed directory (I), and inline data (N).

       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.

       -p project
              Set the file's project 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 have the No_COW attribute set.)

       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 encryption patches to indicate that the file has been
       encrypted.  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,  most of the file's metadata can not be modified, 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 file system is mounted with the "data=ordered" or "data=writeback"
       options and the file system has a journal.  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).

       A  directory  with  the  'P'  attribute set will enforce a hierarchical structure for project id's.  This
       means that files and directory 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 id's much match.  In addition, a hard link to file can only be created when the  project  id  for
       the file and the destination directory match.

       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.

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 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), xfs(5).