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

Michael DeHaan mdehaan at redhat.com
Tue Jul 17 14:37:23 UTC 2007

Adam Rosenwald wrote:
> 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.

Patches accepted -- though this should probably this should go in 
virtinst as it wouldn't apply just to koan.   

>>    or specify --virt-path=/path/to/directory
> What will the full virtual path be then? /path/to/directory/<name>?  
> /path/to/directory/<mac>?

If there is a specified name chosen on the client with --virt-name=bar,
If not...
    For a profile:   /path/to/directory/$macaddress
    For a system:  /path/to/directory/$nameofsystemobject

>>    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'.
Those arguments are, IMHO, slightly confusing.  Partitions start with 
"/dev" (example: /dev/sda4), paths start with "/", so it's clear from 
the path what the user is intending -- and much easier to 
document/understand.   It also helps keep koan/cobbler from getting too 
many new arguments.

> 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!

While I'm not concerned with that, it also would not cause problems with 
the current implementation.

>> 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?

Koan is set to not-require a lot of optional things -- kvm, qemu, xen, 
virtinst -- because the user might just be using --replace-self and we 
do not want to pull in those dependencies.   

>> 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?

They are already implemented -- see upstream source.

> -A.
>> --Michael
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