I’ve been tidying up some of my dedicated servers and needed to remove some of the VMs under KVM setup. This post shows you how to use virsh command to do just that.

List virtual machines using virsh

As you can see, there are quite a few VMs not running and possibly pending decommission:

root@s2:/ # virsh list --all

Id Name State
----------------------------------------------------
1 m running
2 dbm1 running
3 v15 running
- centos7 shut off
- elk shut off
- infra shut off
- jira shut off
- v10.ts.im shut off
- v9.ts.im shut off

List VM storage using virsh

centos7 VM was definitely there for some quick test, so should be safe to remove.

Let’s confirm the virtual disk files it has:

root@s2:/ # virsh dumpxml --domain centos7 | grep source
<source file='/var/lib/libvirt/images/rhel7.0-3.qcow2'/>
<source bridge='vbr1'/>
<source bridge='vbr0'/>

This is a large enough file with virtual disk:

root@s2:/var/lib/docker/containers # ls -lad /var/lib/libvirt/images/rhel7.0-3.qcow2
-rw------- 1 root root 17182752768 Apr 11 2018 /var/lib/libvirt/images/rhel7.0-3.qcow2
root@s2:/var/lib/docker/containers # du -sh /var/lib/libvirt/images/rhel7.0-3.qcow2
17G /var/lib/libvirt/images/rhel7.0-3.qcow2

Remove KVM virtual machine with storage files

Time to remove our virtual machine and its virtual storage:

root@s2:/var/lib/docker/containers # virsh undefine centos7 --remove-all-storage
Domain centos7 has been undefined
Volume 'vda'(/var/lib/libvirt/images/rhel7.0-3.qcow2) removed.

That’s it for today!

See Also

• KVM
• Virtual Machine
• Update VM title with virsh
• How To: enable auto-start for virtual machines in KVM
• HW virtualization

I’m updating and migrating the last few of virtual machines on one of my servers, and realised that there’s a virsh list command option that I really like: it shows descriptive titles in addition to just listing virtual machines.

You know, how we usually run virsh list to see the VMs currently running on a server?

root@s2:/ # virsh list
Id Name State
----------------------------------------------------
1 elk running
4 dbm1 running
6 v9.ts.im running
9 infra running

Well, these VM names aren’t terribly informative. So I like using the virsh list –title command to show the list of VMs with their proper titles:

root@s2:/ # virsh list --title
Id Name State Title
----------------------------------------------------------------------------------
1 elk running Elastic + Logstash + Kibana
4 dbm1 running
6 v9.ts.im running wiki [4vCPU 4GB]
9 infra running infra [4 vCPU 4GB]

And if any VMs are not showing descriptive titles yet, it’s very easy to add it (–live means “apply to the running instance of the VM” and –config means “update the VM information on the disk”). Here’s an example forth dbm1 VM:

root@s2:/ # virsh desc dbm1 --title "MariaDB server [4vCPU 4GB]" --live --config
Domain title updated successfully

…and if we check again, dbm1 VM is now sporting a brand new description:

root@s2:/ # virsh list --title
Id Name State Title
----------------------------------------------------------------------------------
1 elk running Elastic + Logstash + Kibana
4 dbm1 running MariaDB server [4vCPU 4GB]
6 v9.ts.im running wiki [4vCPU 4GB]
9 infra running infra [4 vCPU 4GB]

I had one of my dedicated servers crash the other day and when I fixed it and booted it again, some of my virtual machines didn’t boot.

Turns out, it’s because they didn’t have the autostart enabled:

root@s3:~ # virsh dominfo m
Id: -
Name: m
UUID: f2f9b5aa-7086-89ef-a643-fddb55134ef0
OS Type: hvm
State: shut off
CPU(s): 4
Max memory: 4194304 KiB
Used memory: 4194304 KiB
Persistent: yes
Autostart: disable
Managed save: no
Security model: none
Security DOI: 0

That’s how one can turn the autostart on so that next reboot this VM would start (last parameter is the name of the VM):

root@s3:~ # virsh autostart m     
Domain m marked as autostarted

And just to make sure this actually helped:

root@s3:~ # virsh dominfo m
Id: -
Name: m
UUID: f2f9b5aa-7086-89ef-a643-fddb55134ef0
OS Type: hvm
State: shut off
CPU(s): 4
Max memory: 4194304 KiB
Used memory: 4194304 KiB
Persistent: yes
Autostart: enable
Managed save: no
Security model: none
Security DOI: 0