chattr(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ATTRIBUTES | AUTHOR | BUGS AND LIMITATIONS | AVAILABILITY | SEE ALSO | COLOPHON

CHATTR(1)                General Commands Manual               CHATTR(1)

NAME         top

       chattr - change file attributes on a Linux file system

SYNOPSIS         top

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

DESCRIPTION         top

       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 journalling (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 filesystems; refer
       to filesystem-specific man pages such as btrfs(5), ext4(5), and
       xfs(5) for more filesystem-specific details.

OPTIONS         top

       -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         top

       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 filesystem.  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 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.

       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 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, ext3,
              and ext4 filesystems 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      The 'x' attribute can be set on a directory or file.  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 filesystem 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         top

       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         top

       The 'c', 's',  and 'u' attributes are not honored by the ext2,
       ext3, and ext4 filesystems 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         top

       chattr is part of the e2fsprogs package and is available from
       http://e2fsprogs.sourceforge.net.

SEE ALSO         top

       lsattr(1), btrfs(5), ext4(5), xfs(5).

COLOPHON         top

       This page is part of the e2fsprogs (utilities for ext2/3/4
       filesystems) project.  Information about the project can be found
       at ⟨http://e2fsprogs.sourceforge.net/⟩.  It is not known how to
       report bugs for this man page; if you know, please send a mail to
       man-pages@man7.org.  This page was obtained from the project's
       upstream Git repository
       ⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on
       2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-02-28.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

E2fsprogs version 1.46.2      February 2021                    CHATTR(1)

Pages that refer to this page: chattr(1)lsattr(1)rm(1)fallocate(2)ioctl_iflags(2)mount(2)statx(2)utime(2)utimensat(2)ext4(5)tmpfiles.d(5)xfs(5)btrfs-property(8)xfsdump(8)