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btrfs-progs: docs, btrfs-mount: enhance file attributes section

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Signed-off-by: David Sterba <dsterba@suse.com>
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David Sterba 2016-01-11 15:28:08 +01:00
parent 7ccc0543dc
commit a8829f5335
1 changed files with 43 additions and 14 deletions
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Documentation/btrfs-mount.asciidoc
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@ -8,7 +8,11 @@ btrfs-mount - topics about the BTRFS filesystem (mount options, supported file a
DESCRIPTION
-----------
This document describes topics related to BTRFS that are not specific to the
tools.
tools. Currently covers:
1. mount options
2. file attributes
MOUNT OPTIONS
-------------
@ -332,29 +336,54 @@ root user can do that.
FILE ATTRIBUTES
---------------
The btrfs filesystem supports setting the following file
attributes the `chattr`(1) utility
The btrfs filesystem supports setting the following file attributes using the
`chattr`(1) utility:
*a* -- append only
*a*::
'append only', new writes are always written at the end of the file
*A* -- no atime updates
*A*::
'no atime updates'
*c* -- compressed
*c*::
'compress data', all data written after this attribute is set will be compressed.
Please note that compression is also affected by the mount options or the parent
directory attributes.
+
When set on a directory, all newly created files will inherit this attribute.
*C* -- no copy on write
*C*::
'no copy-on-write', file modifications are done in-place
+
When set on a directory, all newly created files will inherit this attribute.
+
NOTE: due to implementation limitations, this flag can be set/unset only on
empty files.
*d* -- no dump
*d*::
'no dump', makes sense with 3rd party tools like `dump`(8), on BTRFS the
attribute can be set/unset on no other special handling is done
*D* -- synchronous directory updates
*D*::
'synchronous directory updates', for more details search `open`(2) for 'O_SYNC'
and 'O_DSYNC'
*i* -- immutable
*i*::
'immutable', no file data and metadata changes allowed even to the root user as
long as this attribute is set (obviously the exception is unsetting the attribute)
*S* -- synchronous updates
*S*::
'synchronous updates', for more details search `open`(2) for 'O_SYNC' and
'O_DSYNC'
*X* -- no compression
*X*::
'no compression', permanently turn off compression on the given file, other
compression mount options will not affect that
+
When set on a directory, all newly created files will inherit this attribute.
For descriptions of these attribute flags, please refer to the
`chattr`(1) man page.
No other attributes are supported. For the complete list please refer to the
`chattr`(1) manual page.
SEE ALSO
--------