[et-mgmt-tools] Virt-disk-path selection patch and other virt. attributes...

Adam Rosenwald thestrider at gmail.com
Tue Jul 17 00:46:45 UTC 2007

Thanks, Michael!  See inline for comments...

Michael DeHaan wrote:
> I've checked in some modifications to the --virt-path code and 
> rearranged it somewhat.
> To use a standard disk image with koan:
>    leave --virt-path off and assume defaults (like /var/lib/xen/images)
While observing this (reasonable -- although should be documented in 
Koan (if not already)) default, I think a free-space check is in order 
for the filesystem that contains /var/lib/xen/images.  If there is not 
enough free space to accommodate --virt-size, then an error message 
should be printed out.  The current (virtinst?) reaction is to let the 
filesystem fill up to 100% and /then* */alert the user about free 
space.  This doesn't make sense, and either cobbler/koan or dependency 
libraries should show awareness of this problem.
>    or specify --virt-path=/path/to/directory
What will the full virtual path be then? /path/to/directory/<name>?  
>    or specify --virt-path=/path/to/directory/filename
> To use an existing partition:
>    specify --virt-path=/dev/sda4, or equivalent
> To carve out of a chunk of a volume group, of the requested 
> --virt-size, using the name cobbler would ordinarily choose:
>    have an existing LVM volume group named something, such as 
> VolGroup00, with some free space on it
>    specify --virt-path=VolGroup00, or equivalent
>    or be more specific:  --virt-path=VolGroup00 --virt-name=asdf   
> (this creates /dev/mapper/VolGroup00/asdf)
The --virt-name can be confusing with --name.  What's wrong with 
--virt-vg=VolGroup00 --virt-lv=asdf?  Or --virt-path=VG:[LV]?  To make 
the second form clearer, '--virt-path=VolGroup00:' (notice the trailing 
colon) or '--virt-path=VolGroup00:asdf'.

If you were concerned about the rare case where VolGroup or LogVol 
included a colon in the name (e.g. "VolGroup\:" or "Log\:Vol00"), the 
colon-checking could check for the existence of colons in the actual 
filename and ignore them.  Honestly, I don't think anyone would ever 
consciously put a colon in their device name, unless (s)he were mad!  
And this is a reasonable assumption!
> Sidenote -- I've tested the above with qemu-kvm and they perform quite 
> well.    When virt-manager's next-release supports installing these
> via kickstart locations (like Xen), I'll move the kvm bits over to use 
> virtinst -- until then, qemu-kvm systems created with koan do not show up
> in virt-manager and you have to use the standard KVM tools for basic 
> management.   That should change very shortly.
> Additionally I've added a --virt-graphics flag to koan which enables 
> VNC in both virt types ("qemu", "xenpv").    virt-graphics is 
> currently not read as a default
Cool!  Should --virt-graphics check for the existence of vnc?  Or are 
you satisfied with xenlibs' awkward stack tracing output?
> value from cobbler, but it probably should be.  --virt-path and 
> --virt-type can be passed to both koan and cobbler (profile add and 
> system add).
Awesome!  Would you like me to follow your example in implementing the 
other koan virt attributes?  Or do you have these covered?

> --Michael
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> et-mgmt-tools at redhat.com
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