Re: [Xen-devel] starting domain when block device already mounted

[Mark Williamson <Mark.Williamson@xxxxxxxxxxxx>]

> Are you mounting the device within dom0 after creating the domU?  I'm
> not sure there's anything Xend can do about that.

Yes that's correct - if you try and mount domain filesystems read / write 
after the domain is started then it'll probably succeed but the filesystem 
will get hosed.

Even mounting read-only in dom0 will confuse the filesystem driver if the 
domain writes anything.

Cheers,
Mark

> Regards,
>
> James Harper wrote:
> >My disks line is:
> >
> >disk = [ 'phy:vg00/mail,0301,w', 'phy:vg00/mail-swap,0302,w' ]
> >
> >The unpriv domain is up and running again, although I don't know what
> >damage has been done. /etc/passwd was missing though which is not a good
> >sign. I found it in /lost+found, but who knows what else is missing!
> >
> >Thanks
> >
> >James
> >
> >>-----Original Message-----
> >>From: Ian Pratt [mailto:m+Ian.Pratt@xxxxxxxxxxxx]
> >>Sent: Monday, 17 January 2005 09:34
> >>To: James Harper; xen-devel@xxxxxxxxxxxxxxxxxxxxx
> >>Subject: RE: [Xen-devel] starting domain when block device already
> >
> >mounted
> >
> >>>I just had a filesystem hosed in an unpriv domain (ext3
> >>>errors all over
> >>>the place), and then when I went to do a fsck on the block device it
> >>>told me it was already mounted, and sure enough, dom0 already had
> >
> >the
> >
> >>>device mounted. Would that cause a filesystem crash, or at
> >>>least errors?
> >>>Dom0 wasn't doing anything to the filesystem, and the unpriv
> >>>domain had
> >>>been up for a few weeks before this occurred.
> >>
> >>Mounting an ext3 file system writeable in two domains is almost
> >
> >certain
> >
> >>to destroy it.
> >>
> >>The tools try and prevent this. Was it a 'file:' vbd? There's
> >
> >currently
> >
> >>no safety checks for those, but there should be for physical partition
> >>and LVM volumes.
> >>
> >>Ian
> >>
> >>>Anyway, I've done this a few times before by mistake - made a few
> >>>changes to the unpriv domain's filesystem from dom0 and forgot to
> >>>unmount it before starting the domain. Is there any easy way
> >>>to get 'xm
> >>>create' to check before starting that none of the block devices it
> >
> >is
> >
> >>>about to export are in use? Such a thing would probably save me
> >>>countless headaches in the future! (or maybe it's been done
> >>>already? I'm
> >>>running 2.0.1)
> >>>
> >>>Thanks
> >>>
> >>>James
> >>>
> >>>
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