libvirt users - Dec 2014 - Virtual machine removal through command line.

Hi,

Until today, I hadn't found a way to cleanly remove a KVM virtual machine
through command line on CentOS 6 or 7! I had to run 'systemctl restart
libvirtd' or 'service libvirtd restart'

After several months (!!!), I found this thread:
https://github.com/pradels/vagrant-libvirt/issues/107

Now, I know how to cleanly remove a KVM virtual machine (with default file
location):
virsh destroy vm.example.com
virsh undefine vm.example.com --managed-save
/bin/rm /var/lib/libvirt/images/vm.example.com.img
/bin/rm /var/log/libvirt/qemu/vm.example.com.log
virsh vol-delete /var/lib/libvirt/images/vm.example.com.img --pool default

I don't know if the last command ('virsh vol-delete' avoiding the
libvirtd
restart) is a bug or a feature but it must be documented! Only a libvirt
developer can guess something like this.

Feel free to change my instructions in any way you think it's better but at
least document this in a public place (http://wiki.libvirt.org for example).

Regards.

On 18.12.2014 23:35, Le Bris Gilles wrote:
> Hi,
>
> Until today, I hadn't found a way to cleanly remove a KVM virtual
> machine through command line on CentOS 6 or 7! I had to run 'systemctl
> restart libvirtd' or 'service libvirtd restart'
>
> After several months (!!!), I found this thread:
> https://github.com/pradels/vagrant-libvirt/issues/107
>
> Now, I know how to cleanly remove a KVM virtual machine (with default
> file location):
> virsh destroy vm.example.com <http://vm.example.com>
> virsh undefine vm.example.com <http://vm.example.com> --managed-save
> /bin/rm /var/lib/libvirt/images/vm.example.com.img
> /bin/rm /var/log/libvirt/qemu/vm.example.com.log
> virsh vol-delete /var/lib/libvirt/images/vm.example.com.img --pool default
>
> I don't know if the last command ('virsh vol-delete' avoiding
the
> libvirtd restart) is a bug or a feature but it must be documented! Only
> a libvirt developer can guess something like this.
Well, there are basically two ways how to provide a diskt to a VM. The 
first one is to provide a path to the file directly, the other is to 
provide a volume and pool names. It's documented here:

http://libvirt.org/formatdomain.html#elementsDisks

There are plenty of examples, like:

     <disk type='volume' device='disk'>
       <driver name='qemu' type='raw'/>
       <source pool='blk-pool0' volume='blk-pool0-vol0'/>
       <target dev='hdk' bus='ide'/>
     </disk>

Then, when undefying a domain, you can certainly do 'vol-delete'. It 
comes natural if you have it that way.

What's interesting here though, is that restarting the daemon makes VMs 
go away. Although, since you have to pass '--managed-save' to the 
'undefine' command, I guess the libvirt-guests.service is configure to 
managed save you guests. So they are not really gone, rather than saved 
on your disk:

# virsh list --all
  Id    Name                           State
----------------------------------------------------
  -     dummy                          shut off
  -     fedora                         shut off
  -     fedora21                       shut off
  -     freebsd                        shut off
  -     gentoo                         shut off
  -     migt10                         shut off
  -     rhel7                          shut off
  -     win7                           shut off


Michal