How to manage VMs (deb/3.0/CLI)

2.9 3.0 3.1

If you have already created a VM host, you will want to create and delete virtual machines (VMs); this article will explain:

How to add a VM

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/"

How to 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 six constraints:

  1. cores= requested cores
  2. cpu_speed= requested minimum cpu speed in MHz
  3. memory= requested memory in MB
  4. architecture= See Architecture below
  5. storage= See Storage below
  6. interfaces= See Interfaces below

How to set 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"

How to set 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, let’s examine how to compose a machine with the following two disks:

  1. 32 GB disk from storage pool pool1
  2. 64 GB disk from storage pool pool2

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

To find $DISK1_ID and $PARTITION_ID, use maas admin machine read $VM_HOST_ID.

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

To find $DISK2_ID, use maas admin machine read $VM_HOST_ID.

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

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

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

How to specify 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.

How to find a VM host ID

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:


How to delete a VM

maas $PROFILE machine delete $SYSTEM_ID

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

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