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Creating and deleting VMs

If you have created a VM host, you will want to create and delete virtual machines (VMs). You can use either the CLI or the UI for these operations; this article explains how.

Quick questions you may have:

Adding a VM from the Web UI

While on VM host’s details view, select ‘Compose’ from the ‘Take action’ drop-down menu to compose a 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 VM host detail view. In a few moments, your new machine will be auto-commissioned. The ‘Machines’ page will reflect this as well.

MAAS will deduct the new machine’s resources from the VM host’s resources:


Adding a VM from the CLI

To compose a basic VM:

maas $PROFILE vm-host compose $VM_HOST_ID

Example output for default composing:

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

Set resources while adding a VM

Compose with resources specified:

maas $PROFILE vm-host compose $VM_HOST_ID $RESOURCES

Where $RESOURCES is a space-separated list of constraints:

Setting the architecture while adding a VM

To list available architectures:

maas $PROFILE boot-resources read

Then, for example:

maas $PROFILE vm-host compose $VM_HOST_ID \
    cores=40 cpu_speed=2000 memory=7812 architecture="amd64/generic"

Setting storage parameters while adding a VM

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:

where we want the first disk to be a bootable root partition / and the second to be a home directory.

First, create the VM:

maas $PROFILE vm-host compose $VM_HOST_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 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 yo.

maas admin partition delete $VM_HOST_ID $DISK1_ID $PARTITION_ID

[note] To find $DISK1_ID and $PARTITION_ID, use maas admin machine read $VM_HOST_ID. [/note]

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

maas admin partitions create $VM_HOST_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 $VM_HOST_ID $DISK1_ID

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

maas admin partitions create $VM_HOST_ID $DISK2_ID

[note] To find $DISK2_ID, use maas admin machine read $VM_HOST_ID. [/note]

Now, format the partitions. This requires three commands:

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

[note] To find the partition IDs, use maas admin partitions read $VM_HOST_ID $DISK1_ID and maas admin partitions read $VM_HOST_ID $DISK2_ID [/note]

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

Specifying interfaces while adding a VM

Using the interfaces constraint, you can compose virtual machines with interfaces, allowing the selection of VM host 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 you deploy the VM host 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 (matching the VLAN which corresponds to the subnet can be found – e.g. and assigns the IP address to the newly-composed machine upon allocation.

See the Machines MAAS API documentation for a list of all constraint keys.

Find VM host IDs

Here’s a simple way to find a VM host’s ID by name using jq:

maas $PROFILE vm-hosts read | jq '.[] | select (.name=="MyVMHost") | .name, .id'

Example output:


Deleting a VM from the Web UI

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


Deleting a VM with the CLI

maas $PROFILE machine delete $SYSTEM_ID

After you delete a machine, its resources will be available for other VMs.