On 30 October 2012 20:49, Eric Blake <[email protected]> wrote: > On 10/30/2012 08:46 AM, Douglas Russell wrote: > > I'm experimenting with how to attach storage to a guest virtual machine > (I > > sent another message to th elist about that as it's slightly different) > > > > Looking in the XML files for my virtual machine, I see this: > > > > <disk type='file' device='disk'> > > <driver name='qemu' type='qcow2'/> > > <source file='/vm/myvm/tmpeuiVc9.qcow2'/> > > <target dev='hda' bus='ide'/> > > <address type='drive' controller='0' bus='0' unit='0'/> > > </disk> > > > > However, /dev/hda is not a device in the guest. It is /dev/sda. It's not > > really a problem in it's own right, but it's one of several connected > > things which don't make sense. Is there some explanation for this? > > The <target dev='...'> designation is a hint, and there for you to track > things in the host, but does not necessarily reflect the name that the > guest will choose for the same device (there is NO way for the host to > force what the guest names things). >
Ok, that's fair enough, I was wondering how it would go about influencing the guest. > However, for SCSI devices in the guest, you probably want to use <disk > type='block' device='lun'> rather than type='file' device='disk'. > You think I should change the above stanza or are you talking about the second ? The above storage really is a file. > > [Caveat: I haven't used SCSI devices in my guests yet] > > > > > I believe this is linked to some weirdness when I attach some extra > storage > > like so: > > > > virsh attach-disk myvm /dev/lvm-group1/mystorage sdb --driver qemu > > --persistent > > > > This adds the following stanza: > > > > <disk type='block' device='disk'> > > <driver name='qemu' type='raw'/> > > <source dev='/dev/lvm-group1/mystorage'/> > > <target dev='sdb' bus='scsi'/> > > <address type='drive' controller='0' bus='0' unit='1'/> > > </disk> > > > > Looks about right. In the guest though, it pushes /dev/sda (root and swap > > are here on sda1 and sda2) upto /dev/sdb (sdb1 and sdb2). Somehow it > still > > boots correctly despite fstab referrencing /dev/sda1 and /dev/sda2 for / > > and swap. The new /dev/sda is this storage I tried to add as sdb. What > > could be causing this? > > Again, names in the XML don't have to reflect names chosen by the guest. > Beyond that, I don't have quite enough experience in this area of the > code to give a definitive answer, but at least wanted to throw out an > answer while you wait to see if anyone else also replies. > Ok, makes sense. I'm still wondering how it's able to start properly though when the fstab is wrong though? It boots up and mounts /dev/sdb1 on /, fstab still says /dev/sda1 is /. I've also started a new thread as hotplug is also not working for some reason. Thanks.
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