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Use btrfs inspect-internal dump-super to read UUID (!105) 

GParted so far uses 'btrfs filesystem show' to read the file system
UUID.  But this doesn't work on a file system image so doesn't work in
the GitLab CI test jobs, as discussed in the earlier commit "Use btrfs
filesystem label to read the FS label (!105)".
    $ truncate -s 256M /tmp/test.img
    $ mkfs.btrfs /tmp/test.img
    ...
    UUID:               5ea62f88-fef3-4ece-a726-b88f3d81fe1c
    ...
    $ btrfs filesystem show /tmp/test.img
    ERROR: not a valid btrfs filesystem: /tmp/test.img

Instead use 'btrfs inspect-internal dump-super' which works on image
files too.
    $ btrfs inspect-internal dump-super /tmp/test.img
    ...
    fsid                    5ea62f88-fef3-4ece-a726-b88f3d81fe1c
    ...

'btrfs inspect-internal dump-super' was added in btrfs-progs 4.5 [1][2]
so is available in the oldest supported distributions and can be used
unconditionally.
    Distro            EOL        btrfs --version
    Debian 10         2022-Jun   v4.20
    RHEL / CentOS 7   2024-Jun   v4.9.1
    Ubuntu 18.04 LTS  2023-Apr   v4.15.1
    SLES 12 SP5       2024-Oct   v4.5.3    [3][4]

Unfortunately it returns 0 status on failure so use non-empty stderr to
identify failure.
    $ rm /tmp/test.img
    $ truncate -s 256M /tmp/test.img
    $ btrfs inspect-internal dump-super /tmp/test.img 1> /dev/null
    ERROR: bad magic on superblock on /tmp/test.img at 65536
    $ echo $?
    0

[1] btrfs-progs: introduce inspect-internal dump-super
    https://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git/commit/?id=eaa93e3b0295fc94c774ec73056559a6b8c78b42
[2] Btrfs progs release 4.5
    https://lore.kernel.org/linux-btrfs/20160320235330.GG21722@suse.cz/
    "* new/moved commands
       * btrfs-show-super -> btrfs inspect-internal dump-super
    "
[3] SUSE Long Term Service Pack Support
    https://links.imagerelay.com/cdn/3404/ql/f3a083e9bcd34c76addd096d7f60ec00/long_term_service_pack_support_flyer.pdf
[4] SUSE package search
    https://scc.suse.com/packages?name=SUSE%20Linux%20Enterprise%20Server&version=12.5&arch=x86_64&query=btrfsprogs&module=

Closes !105 - Update used btrfs file system commands, new minimum is
              btrfs-progs 4.5
This commit is contained in:
Mike Fleetwood 2022-07-22 17:59:24 +01:00 committed by Curtis Gedak
parent 1fbc8988ff
commit be895fb98e
1 changed files with 15 additions and 15 deletions
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20
src/btrfs.cc
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@ -61,7 +61,8 @@ FS btrfs::get_filesystem_support()
// btrfs filesystem label
// btrfs filesystem resize
// btrfs filesystem show
// as they are all available in btrfs-progs >= 3.12.
// btrfs inspect-internal dump-super
// as they are all available in btrfs-progs >= 4.5.
fs.read = FS::EXTERNAL;
fs .read_label = FS::EXTERNAL ;
@ -363,24 +364,23 @@ void btrfs::read_label(Partition& partition)
void btrfs::read_uuid(Partition& partition)
{
Utils::execute_command("btrfs filesystem show " + Glib::shell_quote(partition.get_path()),
Utils::execute_command("btrfs inspect-internal dump-super " + Glib::shell_quote(partition.get_path()),
output, error, true);
//In many cases the exit status doesn't reflect valid output or an error condition
// so rely on parsing the output to determine success.
Glib::ustring uuid_str = Utils::regexp_label( output, "uuid:[[:blank:]]*(" RFC4122_NONE_NIL_UUID_REGEXP ")" ) ;
if ( ! uuid_str .empty() )
partition .uuid = uuid_str ;
else
// btrfs inspect-internal dump-super returns zero exit status for both success and
// failure. Instead use non-empty stderr to identify failure.
if (! error.empty())
{
if (! output.empty())
partition.push_back_message(output);
if (! error.empty())
partition.push_back_message(error);
return;
}
partition.uuid = Utils::regexp_label(output, "^fsid[[:blank:]]*(" RFC4122_NONE_NIL_UUID_REGEXP ")");
}
bool btrfs::write_uuid( const Partition & partition, OperationDetail & operationdetail )
{
return ! execute_command( "btrfstune -f -u " + Glib::shell_quote( partition.get_path() ),