KVM Archives - apt get life

KVM converting virtual disks from raw img files to qcow2

2020/01/21 by sudo Leave a Comment

If you’re running qemu KVM on Ubuntu and want to take advantage of the qcow2 file format’s snapshotting capabilities and sparse disk population you can easily convert using the command line tool qemu-img convert

First, make sure your virtual machine is turned off! Then you can navigate to the directory your virtual disks are stored in (usually /var/lib/libvirt). It’s probably a good idea to be a root user or otherwise sudo the following command

qemu-img convert -f raw -O qcow2 vm_hdd.img vm_hdd.qcow2

The -f flag tells convert what format it’s reading. If you don’t provide it then it’ll guess based on the file extension.

the -O flag tells convert what file format to output to, again if not provided it’ll guess based on the file extension.

Now you’ve got a qcow2 file, you’ll need to edit the VM configuration

virsh edit vm_name

this will open up an editor for your VM configuration. It’s an XML file, so it’s reasonably easy to follow. What you’re looking for is a disk section so you can change the file extension and disk type

<disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<source file='/var/lib/libvirt/images/rhel62-2.img'/>

<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source file='/var/lib/libvirt/images/rhel62-2.qcow2'/>

Note both “raw” and “img” have been changed to “qcow2” for this disk. Make sure you’ve picked the right disk to edit in the XML. It may be a good idea to take a backup first so you can fall back to the img file if needed!

That should be it, your VM should now boot with the new disk file. Once you’re sure it’s working you can delete the original (or keep it safe somewhere).

More information about KVM can be found on the RedHat website: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/virtualization_deployment_and_administration_guide/index or the Ubuntu wiki https://help.ubuntu.com/community/KVM/Installation

Fixing Error Opening Spice Console SpiceClientGtk missing

2019/05/13 by sudo 2 Comments

When trying to connect to a KVM using Virtual Machine Manager on Linux Mint 19, I receive the error

Error connecting to graphical console. Error opening Spice console, SpiceClientGtk missing.

This is because the host machine is missing the spice GTK client. In ubuntu 19 it’s easy enough to install using apt

sudo apt install gir1.2-spiceclientgtk-3.0

On older Linux Mint installations (18) you may need to run this instead:

sudo apt-get install gir1.2-spice-client-gtk-3.0

Setting up a Bond and Bridge in Netplan on Ubuntu 18.04

2018/09/12 by sudo 2 Comments

For some of my Ubuntu 18.04 servers, I need to run KVM virtual machines which require a bridge to the network so the machines get public LAN IP addresses and aren’t hidden behind NAT. With the server configuration for both my co-location and servers at work the network interfaces are all bonded for fail-over. This means I need a bond to have a bridge ontop of it for the virtual machines to get public IP addresses, while still allowing for failover of the network connection in the event of a network failure.

Research

There are some good examples of setting up netplan here: https://netplan.io/examples

They have a bridge example:

network:
  version: 2
  renderer: networkd
  bridges:
    br0:
      dhcp4: yes
      interfaces:
        - enp3s0

And a bond example:

network:
  version: 2
  renderer: networkd
  bonds:
    bond0:
      dhcp4: yes
      interfaces:
        - enp3s0
        - enp4s0
      parameters:
        mode: active-backup
        primary: enp3s0

But there’s not a clear indication of how to amalgamate the two.

A bond and a bridge

Here’s what I’ve ended up with in ‘/etc/netplan/50-cloud-init.yaml’:

network:
    bridges:
        br0:
            addresses:
            - 192.168.10.30
            dhcp4: false
            gateway4: 192.168.10.1
            nameservers:
                addresses:
                - 192.168.10.1
                - 192.168.10.2
                search: []
            interfaces:
                - bond0
    bonds:
        bond0:
            interfaces:
            - eno1
            - eno2
            parameters:
                mode: active-backup
    ethernets:
        eno1:
            addresses: []
            dhcp4: false
            dhcp6: false
        eno2:
            addresses: []
            dhcp4: false
            dhcp6: false

Note that I’ve obviously defined static IP addresses, but this isn’t a requirement. Just set ‘dhcp4: true’ and remove the ‘address’, ‘gateway’ and ‘nameserver’ sections if you’re using DHCP.

Once the file’s got that setup in it, it’s possible to run:
sudo netplan apply
and you should be able to run ‘networkctl list’ to check the bridge and bond are setup.