VM host networking (deb/2.7/CLI)

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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. This section explains several ways of accomplishing this.

Five questions you may have:

  1. How do I set up a VM host bridge with the MAAS CLI/API?
  2. How do I set up a VM host bridge with netplan?
  3. How do I set up a VM host bridge with libvirt?
  4. How do I set up SSH for use by libvirt?
  5. What else must I do to use LXD VM hosts?

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.

Use the MAAS API to configure a bridge

You can also use the MAAS CLI/API to configure a VM host bridge, with the following procedure:

  1. Select the interface you wish to configure the bridge on. This example uses the boot interface, since the boot interface must be connected to a MAAS controlled network – but any interface is allowed:

     INTERFACE_ID=$(maas $PROFILE machine read $SYSTEM_ID | jq .boot_interface.id)
    
  2. Create the bridge:

      BRIDGE_ID=$(maas $PROFILE interfaces create-bridge $SYSTEM_ID name=br0 parent=$INTERFACE_ID | jq .id)
    
  3. Select the subnet where you want the bridge (this should be a MAAS controlled subnet):

     SUBNET_ID=$(maas $PROFILE subnets read | jq -r '.[] | select(.cidr == "10.0.0.0/24" and .managed == true).id')
    
  4. Connect the bridge to the subnet:

       maas $PROFILE interface link-subnet $SYSTEM_ID $BRIDGE_ID subnet=$SUBNET_ID mode="STATIC" ip_address="10.0.0.101"
    

Use netplan to configure a bridge

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 50-cloud-init.yaml, 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 netplan apply.

Use libvirt to configure a bridge

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:

  1. Disable DHCP on libvirt’s default network, or
  2. Create a new libvirt network maas with 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.

Make LXD available for VM hosting (Beta)

Assuming that you want to use LXD VM hosts --currently a Beta feature – then once a bridge is set up, you need to install the correct version of LXD. Prior to the release of Ubuntu 20.04 LXD was installed using Debian packages. The Debian packaged version of LXD is too old to use with MAAS. If this is the case, you’ll need to remove the LXD Debian packages and install the Snap version. Note that you cannot install both Debian and snap versions, as this creates a conflict.

Removing older versions of LXD

If you’re on a version of Ubuntu older than 20.04, or you have the Debian version of LXD, start the uninstall process with the following command:

sudo apt-get purge -y *lxd* *lxc*

This command should result in output that looks something like this:

Reading package lists... Done
Building dependency tree      
Reading state information... Done
Note, selecting 'lxde-core' for glob '*lxd*'
Note, selecting 'python-pylxd-doc' for glob '*lxd*'
Note, selecting 'python3-pylxd' for glob '*lxd*'
Note, selecting 'python-nova-lxd' for glob '*lxd*'
Note, selecting 'lxde-common' for glob '*lxd*'
Note, selecting 'lxde-icon-theme' for glob '*lxd*'
Note, selecting 'lxde-settings-daemon' for glob '*lxd*'
Note, selecting 'lxde' for glob '*lxd*'
Note, selecting 'lxdm' for glob '*lxd*'
Note, selecting 'lxd' for glob '*lxd*'
Note, selecting 'lxd-tools' for glob '*lxd*'
Note, selecting 'python-pylxd' for glob '*lxd*'
Note, selecting 'lxdm-dbg' for glob '*lxd*'
Note, selecting 'lxde-session' for glob '*lxd*'
Note, selecting 'nova-compute-lxd' for glob '*lxd*'
Note, selecting 'openbox-lxde-session' for glob '*lxd*'
Note, selecting 'python-nova.lxd' for glob '*lxd*'
Note, selecting 'lxd-client' for glob '*lxd*'
Note, selecting 'openbox-lxde-session' instead of 'lxde-session'
Note, selecting 'lxctl' for glob '*lxc*'
Note, selecting 'lxc-common' for glob '*lxc*'
Note, selecting 'python3-lxc' for glob '*lxc*'
Note, selecting 'libclxclient-dev' for glob '*lxc*'
Note, selecting 'lxc-templates' for glob '*lxc*'
Note, selecting 'lxc1' for glob '*lxc*'
Note, selecting 'lxc-dev' for glob '*lxc*'
Note, selecting 'lxc' for glob '*lxc*'
Note, selecting 'liblxc1' for glob '*lxc*'
Note, selecting 'lxc-utils' for glob '*lxc*'
Note, selecting 'vagrant-lxc' for glob '*lxc*'
Note, selecting 'libclxclient3' for glob '*lxc*'
Note, selecting 'liblxc-dev' for glob '*lxc*'
Note, selecting 'nova-compute-lxc' for glob '*lxc*'
Note, selecting 'python-lxc' for glob '*lxc*'
Note, selecting 'liblxc-common' for glob '*lxc*'
Note, selecting 'golang-gopkg-lxc-go-lxc.v2-dev' for glob '*lxc*'
Note, selecting 'lxcfs' for glob '*lxc*'
Note, selecting 'liblxc-common' instead of 'lxc-common'
Package 'golang-gopkg-lxc-go-lxc.v2-dev' is not installed, so not removed
Package 'libclxclient-dev' is not installed, so not removed
Package 'libclxclient3' is not installed, so not removed
Package 'lxc-templates' is not installed, so not removed
Package 'lxctl' is not installed, so not removed
Package 'lxde' is not installed, so not removed
Package 'lxde-common' is not installed, so not removed
Package 'lxde-core' is not installed, so not removed
Package 'lxde-icon-theme' is not installed, so not removed
Package 'lxde-settings-daemon' is not installed, so not removed
Package 'lxdm' is not installed, so not removed
Package 'lxdm-dbg' is not installed, so not removed
Package 'openbox-lxde-session' is not installed, so not removed
Package 'python-lxc' is not installed, so not removed
Package 'python3-lxc' is not installed, so not removed
Package 'vagrant-lxc' is not installed, so not removed
Package 'liblxc-dev' is not installed, so not removed
Package 'lxc-dev' is not installed, so not removed
Package 'nova-compute-lxc' is not installed, so not removed
Package 'nova-compute-lxd' is not installed, so not removed
Package 'python-nova-lxd' is not installed, so not removed
Package 'python-pylxd' is not installed, so not removed
Package 'python-pylxd-doc' is not installed, so not removed
Package 'lxc' is not installed, so not removed
Package 'lxc-utils' is not installed, so not removed
Package 'lxc1' is not installed, so not removed
Package 'lxd-tools' is not installed, so not removed
Package 'python-nova.lxd' is not installed, so not removed
Package 'python3-pylxd' is not installed, so not removed
The following packages were automatically installed and are no longer required:
  dns-root-data dnsmasq-base ebtables libuv1 uidmap xdelta3
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  liblxc-common* liblxc1* lxcfs* lxd* lxd-client*
0 upgraded, 0 newly installed, 5 to remove and 21 not upgraded.
pAfter this operation, 34.1 MB disk space will be freed.
(Reading database ... 67032 files and directories currently installed.)
Removing lxd (3.0.3-0ubuntu1~18.04.1) ...
Removing lxd dnsmasq configuration
Removing lxcfs (3.0.3-0ubuntu1~18.04.2) ...
Removing lxd-client (3.0.3-0ubuntu1~18.04.1) ...
Removing liblxc-common (3.0.3-0ubuntu1~18.04.1) ...
Removing liblxc1 (3.0.3-0ubuntu1~18.04.1) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...
(Reading database ... 66786 files and directories currently installed.)
Purging configuration files for liblxc-common (3.0.3-0ubuntu1~18.04.1) ...
Purging configuration files for lxd (3.0.3-0ubuntu1~18.04.1) ...
Purging configuration files for lxcfs (3.0.3-0ubuntu1~18.04.2) ...
Processing triggers for systemd (237-3ubuntu10.40) ...
Processing triggers for ureadahead (0.100.0-21) ...

You should also autoremove packages no longer needed by LXD:

$ sudo apt-get autoremove -y

Output from this command should be similar to:

Reading package lists... Done
Building dependency tree      
Reading state information... Done
The following packages will be REMOVED:
  dns-root-data dnsmasq-base ebtables libuv1 uidmap xdelta3
0 upgraded, 0 newly installed, 6 to remove and 21 not upgraded.
After this operation, 1860 kB disk space will be freed.
(Reading database ... 66769 files and directories currently installed.)
Removing dns-root-data (2018013001) ...
Removing dnsmasq-base (2.79-1) ...
Removing ebtables (2.0.10.4-3.5ubuntu2.18.04.3) ...
Removing libuv1:amd64 (1.18.0-3) ...
Removing uidmap (1:4.5-1ubuntu2) ...
Removing xdelta3 (3.0.11-dfsg-1ubuntu1) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...

Now install LXD from the Snap:

$ sudo snap install lxd
2020-05-20T22:02:57Z INFO Waiting for restart...
lxd 4.1 from Canonical✓ installed

Refreshing LXD on 20.04

If you are on 20.04 or above LXD should be installed by default, but it’s a good idea to make sure it’s up to date:

$ sudo snap refresh
All snaps up to date.

Initialise LXD prior to use

Once LXD is installed it needs to be configured with lxd init before first use:

$ sudo lxd init

Your interactive output should look something like the following. Note a few points important points about these questions:

  1. Would you like to use LXD clustering? (yes/no) [default=no]: no - MAAS does not support LXD clusters in this Beta version.

  2. Name of the storage back-end to use (btrfs, dir, lvm, zfs, ceph) [default=zfs]: dir - Beta testing has primarily been with dir; other options should work, but less testing has been done, so use at your own risk.

  3. Would you like to connect to a MAAS server? (yes/no) [default=no]: no - When LXD is connected to MAAS containers or virtual machines created by LXD will be automatically added to MAAS as devices. This feature should work, but has limited testing in this Beta version.

  4. Would you like to configure LXD to use an existing bridge or host interface? (yes/no) [default=no]: yes - The bridge LXD creates is isolated and not managed by MAAS. If this bridge is used, you would be able to add the LXD VM host and compose virtual machines, but commissioning, deploying, and any other MAAS action which uses the network will fail – so yes is the correct answer here.

  5. Name of the existing bridge or host interface: br0 - br0 is the name of the bridge the user configured (see sections above) which is connected to a MAAS-managed network.

  6. Trust password for new clients: - This is the password the user will enter when connecting with MAAS.

Would you like to use LXD clustering? (yes/no) [default=no]: no
Do you want to configure a new storage pool? (yes/no) [default=yes]: yes
Name of the new storage pool [default=default]:  
Name of the storage back-end to use (btrfs, dir, lvm, zfs, ceph) [default=zfs]: dir
Would you like to connect to a MAAS server? (yes/no) [default=no]: no
Would you like to create a new local network bridge? (yes/no) [default=yes]: no
Would you like to configure LXD to use an existing bridge or host interface? (yes/no) [default=no]: yes
Name of the existing bridge or host interface: br0
Would you like LXD to be available over the network? (yes/no) [default=no]: yes
pAddress to bind LXD to (not including port) [default=all]:
Port to bind LXD to [default=8443]:
Trust password for new clients:
Again:
Would you like stale cached images to be updated automatically? (yes/no) [default=yes]
Would you like a YAML "lxd init" preseed to be printed? (yes/no) [default=no]:

The host is now ready to be added to MAAS as an LXD VM host. Upon adding the VM host, its own commissioning information will be refreshed.

When composing a virtual machine with LXD, MAAS uses either the ‘maas’ LXD profile, or (if that doesn’t exist) the ‘default’ LXD profile. The profile is used to determine which bridge to use. Users may also add additional LXD options to the profile which are not yet supported in MAAS.

Set up SSH

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

Here, $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 libvirtd group.

Set up SSH (libvirt only)

The maas user on your rack controllers will issue all libvirt commands. Therefore, you’ll need to set up SSH public keys on every rack controller for user maas. First create SSH keys on all rack controllers:

$ sudo -i
root@maas:~$ mkdir -p /var/snap/maas/current/root/.ssh
root@maas:~$ cd /var/snap/maas/current/root/.ssh
root@maas:~$ ssh-keygen -f id_rsa

Next, add the contents of ~maas/.ssh/id_rsa.pub to the VM host user’s ~$USER/.ssh/authorized_keys. To accomplish this, log into your VM host node, via SSH, from a host for which MAAS has a matching public SSH key.