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xen-users
Re: [Xen-users] Using CD drives with Xen 3.0.3 on CentOS 4.4
M.A. Williamson wrote:
I'm afraid you're not going to be able to burn and optical disks from
either paravirt or HVM domains for the time being :-(
Drat. I was looking at using a DomU to run rsnapshot for network
snapshot access, and do DVD burning from those, rather than having to do
it on Dom0.
You *could* add a second IDE controller card to your system, export
that to a guest via the PCI passthrough and then use that to drive a
CD writer, but this would be rather heavyweight and imply trust of the
guest OS.
Hmm. All the drives are SATA, it's only the CD/DVD drive that is IDE.
Adding in another ATA card is begging for pain, especially physically
routing the cables to the CD drive in the 1U servers I'm working with.
That seems unwise.
When USB virtualisation is working (it may already work in HVM) it
should be possible to pass a USB burner through to the guest, and that
would enable this kind of use.
I'm already using an external USB storage device, via the
"file:/dev/sdc1,sdc1,w' syntax, which seems workable for external USB
drives.
Note that the Xen paravirtualised block drive doesn't provide full
CD-ROM emulation: you should be able to mount the filesystem, but
you won't be able to treat it entirely like a CD drive because some
of the special operations will not be supported (eject springs to
mind, but there are other CD-ROM specific operations).
Yeah, that's why I hadn't even considered the file: approach. I may
have to use it after all.
Afraid so, sorry :-( For many uses (e.g. just grabbing some files from
the disk), it should work OK. But you can't just boot off a CD-ROM in
a PV domain, nor can you place CD music, etc.
Yeah. that needs to be made clear. The Xen configuration files simply
accept it and seem to ignore it. Putting in useful error messages would
help.
Thanks. How are you downloading the unstable source?
I get mine using mercurial:
hg clone http://xenbits.xensource.com/xen-unstable.hg
Hmm. I'm not familiar with that source control system. (Ghods know I've
worked with CVS, Perforce, Subversion, and some unspeakable homebrews!)
Is there any reason to prefer it to the others, such as Subvresion which
also supports branching properly?
I'd generally recommend using a release version for production
systems, 3.0.4 being the latest and (hopefull) greatest.
http://xenbits2.xensource.com/xen-3.0.4-testing.hg should contain
3.0.4 + bugfixes that are being tested to be rolled up into the next
3.0.4.x update.
There will be tarballs of 3.0.4 linked off one of the Xen homepages,
once they have been updated. Building your own Xen is reasonably
straightforward once you know your way around the components, and
there should be various HOWTOs hanging around.
Hope that helps. If you still have problems with the CD-ROM we can try
and find a workaround for you.
It did help. I'd be happy to write up such notes and adventures for the
FAQ's or installation notes, but I'm seeing significant divergence
between packages such as RedHat's with the virtmanager tool on top of
it, and the bare Xen tools. Weirdness such as the failure of the RHEL
4.x SRPM published by Xensource to be able to build the documentation
put me off it for a while. Other oddness such as using non-getopt based
command line arguments have also slowed me down. Examples include
arguments using "create" instead of "--create", and alternating the use
of "DomU", and "guest", or of "migrate" and "relocate" in both
configuration files nad actual command line arguments, or the "xm
migrate" command having its flags at the end, just waste my time having
to look up and remember all the different argument structures.
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