From 111f1473bd939e01703458d6165f9a119312450d Mon Sep 17 00:00:00 2001 From: David Sterba Date: Thu, 17 Jan 2019 00:52:09 +0100 Subject: [PATCH] btrfs-progs: docs: document btrfstune -m/-M Signed-off-by: David Sterba --- Documentation/btrfstune.asciidoc | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/Documentation/btrfstune.asciidoc b/Documentation/btrfstune.asciidoc index 5de008a6..1d6bc98d 100644 --- a/Documentation/btrfstune.asciidoc +++ b/Documentation/btrfstune.asciidoc @@ -30,6 +30,25 @@ OPTIONS Allow dangerous changes, e.g. clear the seeding flag or change fsid. Make sure 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 :: +(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:: (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. -U :: -Change fsid to 'UUID'. +Change fsid to 'UUID' in all metadata blocks. + The 'UUID' should be a 36 bytes string in `printf`(3) format '"%08x-%04x-%04x-%04x-%012x"'. 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'. + +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 -filesystem temporarily unmountable. To fix it, rerun 'btrfstune -u' to restore -the UUID and let it complete. +filesystem temporarily unmountable. To fix it, rerun 'btrfstune -u' and let +it complete. -x:: (since kernel: 3.10)