1CHATTR(1)                   General Commands Manual                  CHATTR(1)
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NAME

6       chattr - change file attributes on a Linux file system
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SYNOPSIS

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

12       chattr changes the file attributes on a Linux file system.
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14       The format of a symbolic mode is +-=[aAcCdDeFijmPsStTux].
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16       The  operator '+' causes the selected attributes to be added to the ex‐
17       isting attributes of the files; '-' causes them to be removed; and  '='
18       causes them to be the only attributes that the files have.
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20       The  letters  'aAcCdDeFijmPsStTux'  select  the  new attributes for the
21       files: append only (a), no atime updates (A), compressed (c),  no  copy
22       on  write  (C),  no dump (d), synchronous directory updates (D), extent
23       format (e), case-insensitive directory lookups (F), immutable (i), data
24       journaling (j), don't compress (m), project hierarchy (P), secure dele‐
25       tion (s), synchronous updates (S), no tail-merging (t), top  of  direc‐
26       tory hierarchy (T), undeletable (u), and direct access for files (x).
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28       The  following attributes are read-only, and may be listed by lsattr(1)
29       but not modified by chattr: encrypted (E), indexed directory  (I),  in‐
30       line data (N), and verity (V).
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32       Not  all  flags are supported or utilized by all file systems; refer to
33       file system-specific man pages such as btrfs(5),  ext4(5),  and  xfs(5)
34       for more file system-specific details.
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OPTIONS

37       -R     Recursively change attributes of directories and their contents.
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39       -V     Be verbose with chattr's output and print the program version.
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41       -f     Suppress most error messages.
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43       -v version
44              Set the file's version/generation number.
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46       -p project
47              Set the file's project number.
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ATTRIBUTES

50       a      A  file  with the 'a' attribute set can only be opened in append
51              mode for writing.  Only the superuser or  a  process  possessing
52              the  CAP_LINUX_IMMUTABLE capability can set or clear this attri‐
53              bute.
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55       A      When a file with the 'A' attribute set is  accessed,  its  atime
56              record  is  not  modified.  This avoids a certain amount of disk
57              I/O for laptop systems.
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59       c      A file with the 'c' attribute set is automatically compressed on
60              the  disk  by  the kernel.  A read from this file returns uncom‐
61              pressed data.  A write to this file compresses data before stor‐
62              ing  them  on the disk.  Note: please make sure to read the bugs
63              and limitations section at the end of this document.  (Note: For
64              btrfs,  If the 'c' flag is set, then the 'C' flag cannot be set.
65              Also conflicts with btrfs mount option 'nodatasum')
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67       C      A file with the 'C' attribute set will not be subject  to  copy-
68              on-write  updates.   This flag is only supported on file systems
69              which perform copy-on-write.  (Note: For  btrfs,  the  'C'  flag
70              should  be  set  on  new or empty files.  If it is set on a file
71              which already has data blocks, it is undefined when  the  blocks
72              assigned  to  the file will be fully stable.  If the 'C' flag is
73              set on a directory, it will have no effect on the directory, but
74              new  files created in that directory will have the No_COW attri‐
75              bute set. If the 'C' flag is set, then the 'c'  flag  cannot  be
76              set.)
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78       d      A  file with the 'd' attribute set is not a candidate for backup
79              when the dump(8) program is run.
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81       D      When a directory with the 'D' attribute  set  is  modified,  the
82              changes  are  written synchronously to the disk; this is equiva‐
83              lent to the 'dirsync' mount option applied to a  subset  of  the
84              files.
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86       e      The  'e'  attribute indicates that the file is using extents for
87              mapping the blocks  on  disk.   It  may  not  be  removed  using
88              chattr(1).
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90       E      A  file, directory, or symlink with the 'E' attribute set is en‐
91              crypted by the file system.  This attribute may not  be  set  or
92              cleared  using  chattr(1),  although  it  can  be  displayed  by
93              lsattr(1).
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95       F      A directory with the 'F' attribute set indicates  that  all  the
96              path  lookups  inside that directory are made in a case-insensi‐
97              tive fashion.  This attribute can only be changed in  empty  di‐
98              rectories on file systems with the casefold feature enabled.
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100       i      A  file  with the 'i' attribute cannot be modified: it cannot be
101              deleted or renamed, no link can be created to this file, most of
102              the file's metadata can not be modified, and the file can not be
103              opened in write mode.  Only the superuser or a process  possess‐
104              ing the CAP_LINUX_IMMUTABLE capability can set or clear this at‐
105              tribute.
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107       I      The 'I' attribute is used by the htree code to indicate  that  a
108              directory  is  being  indexed using hashed trees.  It may not be
109              set or cleared using chattr(1), although it can be displayed  by
110              lsattr(1).
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112       j      A file with the 'j' attribute has all of its data written to the
113              ext3 or ext4 journal before being written to the file itself, if
114              the   file   system   is  mounted  with  the  "data=ordered"  or
115              "data=writeback" options and the  file  system  has  a  journal.
116              When  the  file system is mounted with the "data=journal" option
117              all file data is already journalled and this  attribute  has  no
118              effect.    Only  the  superuser  or  a  process  possessing  the
119              CAP_SYS_RESOURCE capability can set or clear this attribute.
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121       m      A file with the 'm' attribute is excluded  from  compression  on
122              file systems that support per-file compression.
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124       N      A  file  with  the 'N' attribute set indicates that the file has
125              data stored inline, within the inode itself. It may not  be  set
126              or  cleared  using  chattr(1),  although  it can be displayed by
127              lsattr(1).
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129       P      A directory with the 'P' attribute set will enforce a hierarchi‐
130              cal  structure  for project id's.  This means that files and di‐
131              rectories created in the directory will inherit the  project  id
132              of  the  directory,  rename operations are constrained so when a
133              file or directory is moved  into  another  directory,  that  the
134              project  ids  must  match.  In addition, a hard link to file can
135              only be created when the project id for the file and the  desti‐
136              nation directory match.
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138       s      When  a  file  with the 's' attribute set is deleted, its blocks
139              are zeroed and written back to the disk.  Note: please make sure
140              to read the bugs and limitations section at the end of this doc‐
141              ument.
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143       S      When a file with the 'S' attribute set is modified, the  changes
144              are written synchronously to the disk; this is equivalent to the
145              'sync' mount option applied to a subset of the files.
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147       t      A file with the 't' attribute will  not  have  a  partial  block
148              fragment  at  the  end  of the file merged with other files (for
149              those file systems which support tail-merging).  This is  neces‐
150              sary  for  applications  such as LILO which read the file system
151              directly, and which don't understand tail-merged  files.   Note:
152              As of this writing, the ext2, ext3, and ext4 file systems do not
153              support tail-merging.
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155       T      A directory with the 'T' attribute will be deemed to be the  top
156              of directory hierarchies for the purposes of the Orlov block al‐
157              locator.  This is a hint to the block allocator used by ext3 and
158              ext4  that  the  subdirectories under this directory are not re‐
159              lated, and thus should be spread apart for allocation  purposes.
160              For  example  it is a very good idea to set the 'T' attribute on
161              the /home directory,  so  that  /home/john  and  /home/mary  are
162              placed  into  separate block groups.  For directories where this
163              attribute is not set, the Orlov  block  allocator  will  try  to
164              group subdirectories closer together where possible.
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166       u      When  a file with the 'u' attribute set is deleted, its contents
167              are saved.  This allows the user  to  ask  for  its  undeletion.
168              Note:  please make sure to read the bugs and limitations section
169              at the end of this document.
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171       x      The 'x' attribute can be set on a directory or file.  If the at‐
172              tribute is set on an existing directory, it will be inherited by
173              all files and subdirectories that are  subsequently  created  in
174              the  directory.   If  an  existing  directory has contained some
175              files and subdirectories, modifying the attribute on the  parent
176              directory  doesn't change the attributes on these files and sub‐
177              directories.
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179       V      A file with the 'V' attribute set  has  fs-verity  enabled.   It
180              cannot  be  written  to,  and the file system will automatically
181              verify all data read from it against a cryptographic  hash  that
182              covers the entire file's contents, e.g. via a Merkle tree.  This
183              makes it possible to efficiently authenticate  the  file.   This
184              attribute may not be set or cleared using chattr(1), although it
185              can be displayed by lsattr(1).
186

AUTHOR

188       chattr was written by Remy Card <Remy.Card@linux.org>.  It is currently
189       being maintained by Theodore Ts'o <tytso@alum.mit.edu>.
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BUGS AND LIMITATIONS

192       The  'c',  's',   and 'u' attributes are not honored by the ext2, ext3,
193       and ext4 file systems as implemented in the current mainline Linux ker‐
194       nels.   Setting  'a'  and 'i' attributes will not affect the ability to
195       write to already existing file descriptors.
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197       The 'j' option is only useful for ext3 and ext4 file systems.
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199       The 'D' option is only useful on Linux kernel 2.5.19 and later.
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AVAILABILITY

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

206       lsattr(1), btrfs(5), ext4(5), xfs(5).
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210E2fsprogs version 1.46.5         December 2021                       CHATTR(1)
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