CHATTR(1)		    General Commands Manual		     CHATTR(1)

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).

E2fsprogs version 1.47.3	   July 2025			     CHATTR(1)