1CHATTR(1) General Commands Manual CHATTR(1)
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6 chattr - change file attributes on a Linux file system
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9 chattr [ -RVf ] [ -v version ] [ -p project ] [ mode ] files...
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12 chattr changes the file attributes on a Linux file system.
13 The format of a symbolic mode is +-=[aAcCdDeFijPsStTu].
15 The operator '+' causes the selected attributes to be added to the
17 existing attributes of the files; '-' causes them to be removed; and
18 '=' causes them to be the only attributes that the files have.
19 The letters 'aAcCdDeFijPsStTu' select the new attributes for the files:
21 append only (a), no atime updates (A), compressed (c), no copy on write
22 (C), no dump (d), synchronous directory updates (D), extent format (e),
23 case-insensitive directory lookups (F), immutable (i), data journalling
24 (j), project hierarchy (P), secure deletion (s), synchronous updates
25 (S), no tail-merging (t), top of directory hierarchy (T), and
26 undeletable (u).
27 The following attributes are read-only, and may be listed by lsattr(1)
29 but not modified by chattr: encrypted (E), indexed directory (I),
30 inline data (N), and verity (V).
31 Not all flags are supported or utilized by all filesystems; refer to
33 filesystem-specific man pages such as btrfs(5), ext4(5), and xfs(5) for
34 more filesystem-specific details.
35
37 -R Recursively change attributes of directories and their contents.
38 -V Be verbose with chattr's output and print the program version.
40 -f Suppress most error messages.
42 -v version
44 Set the file's version/generation number.
45 -p project
47 Set the file's project number.
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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
53 attribute.
54 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.
58 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.
64 C A file with the 'C' attribute set will not be subject to copy-
66 on-write updates. This flag is only supported on file systems
67 which perform copy-on-write. (Note: For btrfs, the 'C' flag
68 should be set on new or empty files. If it is set on a file
69 which already has data blocks, it is undefined when the blocks
70 assigned to the file will be fully stable. If the 'C' flag is
71 set on a directory, it will have no effect on the directory, but
72 new files created in that directory will have the No_COW
73 attribute set.)
74 d A file with the 'd' attribute set is not a candidate for backup
76 when the dump(8) program is run.
77 D When a directory with the 'D' attribute set is modified, the
79 changes are written synchronously to the disk; this is equiva‐
80 lent to the 'dirsync' mount option applied to a subset of the
81 files.
82 e The 'e' attribute indicates that the file is using extents for
84 mapping the blocks on disk. It may not be removed using
85 chattr(1).
86 E A file, directory, or symlink with the 'E' attribute set is
88 encrypted by the filesystem. This attribute may not be set or
89 cleared using chattr(1), although it can be displayed by
90 lsattr(1).
91 F A directory with the 'F' attribute set indicates that all the
93 path lookups inside that directory are made in a case-insensi‐
94 tive fashion. This attribute can only be changed in empty
95 directories on file systems with the casefold feature enabled.
96 i A file with the 'i' attribute cannot be modified: it cannot be
98 deleted or renamed, no link can be created to this file, most of
99 the file's metadata can not be modified, and the file can not be
100 opened in write mode. Only the superuser or a process possess‐
101 ing the CAP_LINUX_IMMUTABLE capability can set or clear this
102 attribute.
103 I The 'I' attribute is used by the htree code to indicate that a
105 directory is being indexed using hashed trees. It may not be
106 set or cleared using chattr(1), although it can be displayed by
107 lsattr(1).
108 j A file with the 'j' attribute has all of its data written to the
110 ext3 or ext4 journal before being written to the file itself, if
111 the file system is mounted with the "data=ordered" or
112 "data=writeback" options and the file system has a journal.
113 When the filesystem is mounted with the "data=journal" option
114 all file data is already journalled and this attribute has no
115 effect. Only the superuser or a process possessing the
116 CAP_SYS_RESOURCE capability can set or clear this attribute.
117 N A file with the 'N' attribute set indicates that the file has
119 data stored inline, within the inode itself. It may not be set
120 or cleared using chattr(1), although it can be displayed by
121 lsattr(1).
122 P A directory with the 'P' attribute set will enforce a hierarchi‐
124 cal structure for project id's. This means that files and
125 directories created in the directory will inherit the project id
126 of the directory, rename operations are constrained so when a
127 file or directory is moved into another directory, that the
128 project ids must match. In addition, a hard link to file can
129 only be created when the project id for the file and the desti‐
130 nation directory match.
131 s When a file with the 's' attribute set is deleted, its blocks
133 are zeroed and written back to the disk. Note: please make sure
134 to read the bugs and limitations section at the end of this doc‐
135 ument.
136 S When a file with the 'S' attribute set is modified, the changes
138 are written synchronously to the disk; this is equivalent to the
139 'sync' mount option applied to a subset of the files.
140 t A file with the 't' attribute will not have a partial block
142 fragment at the end of the file merged with other files (for
143 those filesystems which support tail-merging). This is neces‐
144 sary for applications such as LILO which read the filesystem
145 directly, and which don't understand tail-merged files. Note:
146 As of this writing, the ext2, ext3, and ext4 filesystems do not
147 support tail-merging.
148 T A directory with the 'T' attribute will be deemed to be the top
150 of directory hierarchies for the purposes of the Orlov block
151 allocator. This is a hint to the block allocator used by ext3
152 and ext4 that the subdirectories under this directory are not
153 related, and thus should be spread apart for allocation pur‐
154 poses. For example it is a very good idea to set the 'T'
155 attribute on the /home directory, so that /home/john and
156 /home/mary are placed into separate block groups. For directo‐
157 ries where this attribute is not set, the Orlov block allocator
158 will try to group subdirectories closer together where possible.
159 u When a file with the 'u' attribute set is deleted, its contents
161 are saved. This allows the user to ask for its undeletion.
162 Note: please make sure to read the bugs and limitations section
163 at the end of this document.
164 V A file with the 'V' attribute set has fs-verity enabled. It
166 cannot be written to, and the filesystem will automatically ver‐
167 ify all data read from it against a cryptographic hash that cov‐
168 ers the entire file's contents, e.g. via a Merkle tree. This
169 makes it possible to efficiently authenticate the file. This
170 attribute may not be set or cleared using chattr(1), although it
171 can be displayed by lsattr(1).
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174 chattr was written by Remy Card <Remy.Card@linux.org>. It is currently
175 being maintained by Theodore Ts'o <tytso@alum.mit.edu>.
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178 The 'c', 's', and 'u' attributes are not honored by the ext2, ext3,
179 and ext4 filesystems as implemented in the current mainline Linux ker‐
180 nels. Setting 'a' and 'i' attributes will not affect the ability to
181 write to already existing file descriptors.
182 The 'j' option is only useful for ext3 and ext4 file systems.
184 The 'D' option is only useful on Linux kernel 2.5.19 and later.
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188 chattr is part of the e2fsprogs package and is available from
189 http://e2fsprogs.sourceforge.net.
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192 lsattr(1), btrfs(5), ext4(5), xfs(5).
193E2fsprogs version 1.45.6 March 2020 CHATTR(1)