[Lustre-discuss] Force read-only ost mount

[Andreas Dilger]

On 2011-06-29, at 10:37 AM, Zachary Beebleson wrote:
> Is there a way to manually mount an ost read-only? I tried 'mount -t 
> lustre -o ro ost_device mountpoint', but got a
> 
> mount.lustre: mount /dev/data1recov/ost1 at /mnt/os1brecov failed: 
> Transport endpoint is not connected
> 
> I know if lustre detects a serious enough problem, ldiskfs error say, it 
> will remount the ost read-only, but I would like to manually force this.

There was a patch in bugzilla related to this, but it likely needs to be
updated.  Some of the mount-time code tries to write to the filesystem,
and that needs to be disabled.

> A raid logical volume on an oss has some problems and I'm trying to 
> transfer one of two osts to another oss (I believe this is possible by 
> umounting lustre from all servers/clients, executing a 'tunefs.lustre 
> --writeconf' on all lustre servers and the related devices, and 
> remounting --- with the copied ost replacing the problematic one).
> 
> In order to minimize downtime, I would like to work with a static ost image 
> -- so I can transfer a faithful copy back, after I repair the raid 
> problem. I did deactivate the ost device on the mds, but I'm worried about 
> changes to files that live on the ost (I wasn't planning on creating 
> another image).


Cheers, Andreas
--
Andreas Dilger 
Principal Engineer
Whamcloud, Inc.