.B chattr
changes the file attributes on a Linux file system.
.PP
-The format of a symbolic mode is +-=[aAcCdDeijPsStTu].
+The format of a symbolic mode is +-=[aAcCdDeFijmPsStTux].
.PP
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.
.PP
-The letters 'aAcCdDeFijPsStTu' select the new attributes for the files:
+The letters 'aAcCdDeFijmPsStTux' select the new attributes for the files:
append only (a),
no atime updates (A),
compressed (c),
extent format (e),
case-insensitive directory lookups (F),
immutable (i),
-data journalling (j),
+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),
-and undeletable (u).
+undeletable (u),
+and direct access for files (x).
.PP
The following attributes are read-only, and may be listed by
.BR lsattr (1)
inline data (N),
and verity (V).
.PP
-Not all flags are supported or utilized by all filesystems; refer to
-filesystem-specific man pages such as
+Not all flags are supported or utilized by all file systems; refer to
+file system-specific man pages such as
.BR btrfs (5),
.BR ext4 (5),
and
.BR xfs (5)
-for more filesystem-specific details.
+for more file system-specific details.
.SH OPTIONS
.TP
.B \-R
.BI \-p " project"
Set the file's project number.
.SH ATTRIBUTES
-A file with the 'a' attribute set can only be open in append mode for writing.
-Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE
-capability can set or clear this attribute.
-.PP
+.TP
+.B 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.
+.TP
+.B 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.
-.PP
+.TP
+.B 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.
-.PP
+document. (Note: For btrfs, If the 'c' flag is set, then the 'C' flag
+cannot be set. Also conflicts with btrfs mount option 'nodatasum')
+.TP
+.B 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
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.)
-.PP
-A file with the 'd' attribute set is not candidate for backup when the
+have the No_COW attribute set. If the 'C' flag is set, then the 'c' flag
+cannot be set.)
+.TP
+.B d
+A file with the 'd' attribute set is not a candidate for backup when the
.BR dump (8)
program is run.
-.PP
+.TP
+.B D
When a directory with the 'D' attribute set is modified,
-the changes are written synchronously on the disk; this is equivalent to
+the changes are written synchronously to the disk; this is equivalent to
the 'dirsync' mount option applied to a subset of the files.
-.PP
+.TP
+.B e
The 'e' attribute indicates that the file is using extents for mapping
the blocks on disk. It may not be removed using
.BR chattr (1).
-.PP
-The 'E' attribute is used by the experimental encryption patches to
-indicate that the file has been encrypted. It may not be
-set or reset using
+.TP
+.B 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
.BR chattr (1),
although it can be displayed by
.BR lsattr (1).
-.PP
+.TP
+.B 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.
-.PP
+.TP
+.B 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.
-.PP
+.TP
+.B 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 reset using
+is being indexed using hashed trees. It may not be set or cleared using
.BR chattr (1),
although it can be displayed by
.BR lsattr (1).
-.PP
+.TP
+.B 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
+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.
-.PP
+.TP
+.B m
+A file with the 'm' attribute is excluded from compression on file
+systems that support per-file compression.
+.TP
+.B 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 reset using
+stored inline, within the inode itself. It may not be set or cleared
+using
.BR chattr (1),
although it can be displayed by
.BR lsattr (1).
-.PP
+.TP
+.B P
A directory with the 'P' attribute set will enforce a hierarchical
-structure for project id's. This means that files and directory created
+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 id's much match. In addition, a
+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.
-.PP
+.TP
+.B 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.
-.PP
+.TP
+.B S
When a file with the 'S' attribute set is modified,
-the changes are written synchronously on the disk; this is equivalent to
+the changes are written synchronously to the disk; this is equivalent to
the 'sync' mount option applied to a subset of the files.
-.PP
+.TP
+.B 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
+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 filesystem directly, and which don't understand tail-merged
-files. Note: As of this writing, the ext2 or ext3 filesystems do not
-(yet, except in very experimental patches) support tail-merging.
-.PP
+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.
+.TP
+.B 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
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.
-.PP
+.TP
+.B 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.
-.PP
+.TP
+.B 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.
+.TP
+.B 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
+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 reset using
+authenticate the file. This attribute may not be set or cleared using
.BR chattr (1),
although it can be displayed by
.BR lsattr (1).
maintained by Theodore Ts'o <tytso@alum.mit.edu>.
.SH BUGS AND LIMITATIONS
The 'c', 's', and 'u' attributes are not honored
-by the ext2, ext3, and ext4 filesystems as implemented in the current
+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.
git://git.whamcloud.com / tools / e2fsprogs.git / blobdiff