[CentOS-virt] Problem with cdrom device on guest

Thu Feb 13 17:15:49 UTC 2014
James B. Byrne <byrnejb at harte-lyne.ca>

I have a kvm guest running MS-WinV7 on a CentOS-6.5 host.  The WinV7 guest was
 installed from a CD.  It installed correctly and was updated and added to an
MS Active Domain without difficulty.  I was able to do work on it through the
virt-manager console and I was able to shut the system down from the console
without problem.

I cannot get it to restart however.

virsh start brws-ms-v7-37v.brockley.harte-lyne.ca
error: Failed to start domain brws-ms-v7-37v.brockley.harte-lyne.ca
error: cannot open file '/dev/sr0': No medium found

I found this bugzilla report.


Which is curiously marked as CLOSED DEFERRED.

The last comment in that bug contains this:
> Summary of findings so far:
> format=raw doesn't work with /dev/sr0.  Omitting format=raw works.
> format=host_device works.
> Apparently, virt-manager specifically asks for "raw".
> Things are different in RHEL-6: format=raw works,
> format=host_device doesn't, format=host_cdrom does
> (doesn't exist in RHEL-5).

Now, in my configuration files there is no 'format' attribute found in any
tag.  I find 'type=raw' inside of many <device/> tags but it seems strange to
me that a RedHat bug report would use such imprecise language so as to confuse
the attribute 'type' with one named 'format' so I wonder if a syntax change
has occurred and if that has introduced a regression?

virsh edit brws-ms-v7-37v.brockley.harte-lyne.ca show this configuration entry
for device sr0:

     30     <disk type='block' device='cdrom'>
     31       <driver name='qemu' type='raw'/>
     32       <source dev='/dev/sr0'/>
     33       <target dev='hdc' bus='ide'/>
     34       <readonly/>
     35       <address type='drive' controller='0' bus='1' target='0' unit='0'/>
     36     </disk>

Despite the inference I draw from the bug report, that format ~= type, one
cannot in fact change the driver attribute 'type' to any value other than raw.
 Any attempt to do so results in this message:

unsupported configuration: unknown driver format value 'host_cdrom'
Failed. Try again? [y,n,f,?]:

Further, the value 'f' is not permitted so one cannot forcibly save the
configuration to determine if in fact it might work.

Has anyone else run into this?  What is the fix?

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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
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