Compose a VM

While on KVM host's details view, select 'Compose' from the 'Take action' drop-down menu to compose a machine.

pod compose machine

You can choose which storage pool to use from a drop-down list:


Click the 'Compose machine' button when you're finished. MAAS will present the pod detail view. In a few moments, your new machine will be auto-commissioned. The 'Machines' page will reflect this as well.

The new machine's resources will be deducted from the pod's resources:

pod compose machine commissioning



To compose a basic pod VM:

maas $PROFILE pod compose $POD_ID

Example output for default composing:

    "system_id": "73yxmc",
    "resource_uri": "/MAAS/api/2.0/machines/73yxmc/"

Set resources

Compose with resources specified:

maas $PROFILE pod compose $POD_ID $RESOURCES

Where RESOURCES is a space-separated list from:

cores=requested cores
cpu_speed=requested minimum cpu speed in MHz
memory=requested memory in MB
architecture= See Architecture below
storage= See Storage below
interfaces= See Interfaces below


To list available architectures:

maas $PROFILE boot-resources read

Then, for example:

maas $PROFILE pod compose $POD_ID \
    cores=40 cpu_speed=2000 memory=7812 architecture="amd64/generic"


Storage parameters look like this:

storage="<label>:<size in GB>(<storage pool name>),<label>:<size in GB>(<storage pool name>)"

For example, to compose a machine with the following disks:

  • 32 GB disk from storage pool pool1
  • 64 GB disk from storage pool pool2

Where we want the first to be used as a bootable root partition / and the second to be used as a home directory.

First, create the VM:

maas $PROFILE pod compose $POD_ID "storage=mylabel:32(pool1),mylabel:64(pool2)"

Note that the labels, here mylabel, are an ephemeral convenience that you might find useful in scripting MAAS actions.

MAAS will create a pod VM with 2 disks, /dev/vda (32 GB) and /dev/vdb (64 GB). After MAAS enlists, commissions and acquires the machine, you can edit the disks before deploying to suit your needs. For example, we'll set a boot, root and home partition.

We'll start by deleting the / partition MAAS created because we want a separate /boot partition to demonstrate how this might be done.

maas admin partition delete $POD_ID $DISK1_ID $PARTITION_ID

Note: To find $DISK1_ID and $PARTITION_ID, use maas admin machine read $POD_ID.

Now, create a boot partition (~512MB):

maas admin partitions create $POD_ID $DISK1_ID size=512000000 bootable=True

We'll use the remaining space for the root partition, so create another without specifying size:

maas admin partitions create $POD_ID $DISK1_ID

Finally, create a partition to use as the home directory. Here we'll use the entire space:

maas admin partitions create $POD_ID $DISK2_ID

Note: To find $DISK2_ID, use maas admin machine read $POD_ID.

Now, format the partitions. This requires three commands:

maas admin partition format $POD_ID $DISK1_ID $BOOT_PARTITION_ID fstype=ext2
maas admin partition format $POD_ID $DISK1_ID $ROOT_PARTITION_ID fstype=ext4
maas admin partition format $POD_ID $DISK2_ID $HOME_PARTITION_ID fstype=ext4

Note: To find the partition IDs, use maas admin partitions read $POD_ID $DISK1_ID and maas admin partitions read $POD_ID $DISK2_ID

Before you can deploy the machine with our partition layout, you need to mount the new partitions. Here, we'll do that in three commands:

maas admin partition mount $SYSTEM_ID $DISK1_ID $BOOT_PARTITION_ID "mount_point=/boot"
maas admin partition mount $SYSTEM_ID $DISK1_ID $ROOT_PARTITION_ID "mount_point=/"
maas admin partition mount $SYSTEM_ID $DISK2_ID $HOME_PARTITION_ID "mount_point=/home"

Finally, we deploy the machine. MAAS will use the partitions as we have defined them, similar to a normal Ubuntu desktop install:

maas admin machine deploy $SYSTEM_ID


Using the interfaces constraint, you can compose virtual machines with interfaces, allowing the selection of pod NICs.

If you don't specify an interfaces constraint, MAAS maintains backward compatibility by checking for a maas network, then a default network to which to connect the virtual machine.

If you specify an interfaces constraint, MAAS creates a bridge or macvlan attachment to the networks that match the given constraint. MAAS prefers bridge interface attachments when possible, since this typically results in successful communication.

Consider the following interfaces constraint:


Assuming the pod is deployed on a machine or controller with access to the maas and storage spaces, MAAS will create an eth0 interface bound to the maas space and an eth1 interface bound to the storage space.

Another example tells MAAS to assign unallocated IP addresses:


MAAS automatically converts the ip constraint to a VLAN constraint (for the VLAN where its subnet can be found -- e.g. and assigns the IP address to the newly-composed machine upon allocation.

See the Machines MAAS API documentation (op=allocate) for a list of all constraint keys.

Find pod IDs

Here's a simple way to find a pod's ID by name using jq:

maas $PROFILE pods read | jq '.[] | select (.name=="MyPod") | .name, .id'

Note: jq is a command-line JSON processor.

Example output:


Delete a machine

To delete a machine, simply delete it as you would any other MAAS node. Select the desired machine from the list of machines and select 'Delete' from the 'Take Action' menu.

pod decompose machine


Delete a VM

maas $PROFILE machine delete $SYSTEM_ID

After a machine is deleted, the machine's resources will be available for other VMs.