# chattr

## 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).
    


## 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.
    


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