Mount multiple file system with the same UUID

Mount multiple file system with the same UUID

[WangMike]

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Dear all,

We know that one cannot mount multiple btrfs file systems which contain the same UUID (for example, snapshot ).

Is it possible to make use of "mount namespace" achieve that? means, if the btrfs file system in different namespace can contain the same UUID.


Thanks
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Re: Mount multiple file system with the same UUID

[David Goodwin]

On 17/04/15 10:20, WangMike wrote:
> Dear all,
>
> We know that one cannot mount multiple btrfs file systems which contain the same UUID (for example, snapshot ).
>
> Is it possible to make use of "mount namespace" achieve that? means, if the btrfs file system in different namespace can contain the same UUID.
>

I've encountered this problem using EC2 EBS volumes.

(the 'ghost image' (AMI) contains btrfs filesystems. This results in all 
child VMs having EBS volumes sharing the same UUID ... and it's then not 
being possible to move volumes around.)

I'm interested to know if there's a possible solution, aside hoping you 
can run mkfs.btrfs on first boot...

David.

Re: Mount multiple file system with the same UUID

[Chris Murphy]

Looks like XFS v5 and ext4 checksums include fs UUID throughout the
filesystem metadata. For XFS changing the UUID has been disabled in
xfs_admin whereas tune2fs supports changing it (which I'd think could
take quite a while). Btrfs supports it via seed device + device add +
removing seed which also can take quite a while.

Anyway, three file systems are (or are about to be) affected by this
so a general purpose solution seems in order.

http://oss.sgi.com/archives/xfs/2015-04/msg00023.html
http://comments.gmane.org/gmane.comp.file-systems.ext4/44464
https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Checksums

Chris Murphy