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btrfs-progs: docs: document btrfstune -m/-M 

Signed-off-by: David Sterba <dsterba@suse.com>
master
David Sterba 2019-01-17 00:52:09 +01:00
parent 45c2b3bb89
commit 111f1473bd
1 changed files with 25 additions and 3 deletions
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28
Documentation/btrfstune.asciidoc
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@ -30,6 +30,25 @@ OPTIONS
Allow dangerous changes, e.g. clear the seeding flag or change fsid. Make sure Allow dangerous changes, e.g. clear the seeding flag or change fsid. Make sure
that you are aware of the dangers. that you are aware of the dangers.
-m::
(since kernel: 5.0)
+
change fsid stored as 'metadata_uuid' to a randomly generated UUID,
see also '-U'
-M <UUID>::
(since kernel: 5.0)
+
change fsid stored as 'metadata_uuid' to a given UUID, see also '-U'
+
The metadata_uuid is stored only in the superblock and is a backward
incompatible change. The fsid in metadata blocks remains unchanged and
is not overwritten, thus the whole operation is significantly faster than
'-U'.
+
The new metadata_uuid can be used for mount by UUID and is also used to
identify devices of a multi-device filesystem.
-n:: -n::
(since kernel: 3.14) (since kernel: 3.14)
+ +
@ -60,16 +79,19 @@ Change fsid to a randomly generated UUID or continue previous fsid change
operation in case it was interrupted. operation in case it was interrupted.
-U <UUID>:: -U <UUID>::
Change fsid to 'UUID'. Change fsid to 'UUID' in all metadata blocks.
+ +
The 'UUID' should be a 36 bytes string in `printf`(3) format The 'UUID' should be a 36 bytes string in `printf`(3) format
'"%08x-%04x-%04x-%04x-%012x"'. '"%08x-%04x-%04x-%04x-%012x"'.
If there is a previous unfinished fsid change, it will continue only if the If there is a previous unfinished fsid change, it will continue only if the
'UUID' matches the unfinished one or if you use the option '-u'. 'UUID' matches the unfinished one or if you use the option '-u'.
+ +
All metadata blocks are rewritten, this may take some time, but the final
filesystem compatibility is unaffected, unlike '-M'.
+
WARNING: Cancelling or interrupting a UUID change operation will make the WARNING: Cancelling or interrupting a UUID change operation will make the
filesystem temporarily unmountable. To fix it, rerun 'btrfstune -u' to restore filesystem temporarily unmountable. To fix it, rerun 'btrfstune -u' and let
the UUID and let it complete. it complete.
-x:: -x::
(since kernel: 3.10) (since kernel: 3.10)