How to manage VM hosts (snap/3.1/UI)
In order to deploy a VM host in your MAAS network, you first need to set up a bridge to connect between your VM host and MAAS itself. Once that’s done, you can add and manage VM hosts – and subsequently, create VMs to act as MAAS machines. This article explains:
- How to set up a VM host bridge with the web UI
- How to set up a VM host bridge with netplan
- How to set up a VM host bridge with libvirt
- How to set up SSH for use by libvirt
- How to add a VM host
- How to configure a VM host
To enable VM host networking features, MAAS must match the VM host IP address of a potential VM host with a known device (a machine or controller). For example, if a machine not known to MAAS is set up as a VM host, enhanced interface selection features will not be available.
It’s essential to enforce usage of IP addresses to avoid domain name conflicts, should different controllers resolve the same domain name with different IP addresses. You should also avoid using 127.0.0.1 when running multiple controllers, as it would confuse MAAS.
You can use the MAAS UI to configure a bridge to connect a VM host to MAAS:
Select the machine you want to use as a VM host, switch to the “Network” tab. Select the network where you want to create the bridge and click “Create bridge:”
Configure the bridge on a subnet MAAS controls. You may use any IP mode for the bridge:
When you’re done, it should look something like this:
Then you can deploy Ubuntu.
You can also use netplan to configure a VM host bridge:
Open your netplan configuration file. This should be in
/etc/netplan. It could be called
netplan.yaml, or something else. Modify the file to add a bridge, using the example below to guide you:
network: bridges: br0: addresses: - 10.0.0.101/24 gateway4: 10.0.0.1 interfaces: - enp1s0 macaddress: 52:54:00:39:9d:f9 mtu: 1500 nameservers: addresses: - 10.0.0.2 search: - maas parameters: forward-delay: 15 stp: false ethernets: enp1s0: match: macaddress: 52:54:00:39:9d:f9 mtu: 1500 set-name: enp1s0 enp2s0: match: macaddress: 52:54:00:df:87:ac mtu: 1500 set-name: enp2s0 enp3s0: match: macaddress: 52:54:00:a7:ac:46 mtu: 1500 set-name: enp3s0 version: 2
Apply the new configuration with
It is also possible to use libvirt to configure a virtual bridge. This method will also work for LXD VM hosts running on Ubuntu. Be aware that other methods may be required if you are configuring LXD on an OS other than Ubuntu.
By default, libvirt creates a virtual bridge,
virbr0, through which VMs communicate with each other and the Internet. DHCP, supplied by libvirt, automatically assigns an IP address to each VM. However, to enable network booting in MAAS, you’ll need to provide DHCP in MAAS and either:
- Disable DHCP on libvirt’s
- Create a new libvirt network
maaswith DHCP disabled.
You can set up such a
maas network like this:
cat << EOF > maas.xml <network> <name>maas</name> <forward mode='nat'> <nat> <port start='1024' end='65535'/> </nat> </forward> <dns enable="no" /> <bridge name='virbr1' stp='off' delay='0'/> <domain name='testnet'/> <ip address='172.16.99.1' netmask='255.255.255.0'> </ip> </network> EOF virsh net-define maas.xml
Note that this network also has NAT port forwarding enabled to allow VMs to communicate with the Internet at large. Port forwarding is very useful in test environments.
For MAAS to successfully communicate with libvirt on your VM host machine – whether you’re running from snap or package, or running rack controllers in LXD containers or on localhost – this example command must succeed from every rack controller:
virsh -c qemu+ssh://$USER@$VM_HOST_IP/system list --all
$USER is a user on your VM host who is a member of the
libvirtd Unix group on the VM host, and
$VM_HOST_IP is the IP of your VM host. Note that insufficient permissions for
$USER may cause the
virsh command to fail with an error such as
failed to connect to the hypervisor. Check the
$USER group membership to make sure
$USER is a member of the
If you installed MAAS via snap, then create the needed SSH keys this way:
sudo mkdir -p /var/snap/maas/current/root/.ssh cd /var/snap/maas/current/root/.ssh sudo ssh-keygen -f id_rsa
Finally, on the VM host, you’ll need to add
id_rsa.pub to the
authorized_keys file in
<vm-host-user-homedir-name> is the name of your VM host user.
After installing MAAS, the ‘KVM’ page is typically empty:
If you want to add a LXD (or libvirt) KVM host to a machine which is already installed, you can do so with the ‘Add KVM’ button:
Upon selecting “Authenticate” (assuming successful authentication), you will receive a project selection screen similar to this:
You must either enter a new project name (which cannot contain spaces or special characters), or you must select an existing project. If you’re not really planning on using projects, selecting the “default” project will allow you to continue working as you have in the past.
MAAS will automatically discover and store the resources your VM host contains. Any existing machines will also appear on the ‘Machines’ page, and MAAS will automatically attempt to commission them.
VM hosts have several configuration options. Modify these by selecting the ‘Configuration’ tab and editing options directly. These options include a VM host’s location, password, network zone, resource pool, and memory and CPU overcommit sliders.