CLI composable hardware

This article provides a list of examples of VM host management tasks you can perform with the MAAS CLI.

Fourteen questions you may have:

  1. How do I get started with the MAAS CLI?
  2. What should I know about VM hosts?
  3. How can I add a VM host?
  4. How can I find VM host IDs?
  5. How can I list resources of all VM hosts?
  6. How can I list resources of a VM host?
  7. How can I update a VM host’s configuration?
  8. How can I list a VM host’s connection parameters?
  9. How can I compose VMs?
  10. How can I compose and allocate a VM?
  11. How can I list machine parameters?
  12. How can I use libvirt storage pools?
  13. How can I delete a VM?
  14. How can I delete a VM host?

Add a VM host

To add a VM host:

maas $PROFILE vm-hosts create type=$VM_HOST_TYPE power_address=$POWER_ADDRESS \
    [power_user=$USERNAME] [power_pass=$PASSWORD] [zone=$ZONE] \

Both USERNAME and PASSWORD are optional for the virsh power type. ZONE and TAGS are optional for all VM hosts.

See the API reference for a listing of available power types.

For example, to create an RSD VM host:

maas $PROFILE vm-hosts create type=rsd power_address= \
    power_user=admin power_pass=admin

And to create a KVM host:

maas $PROFILE vm-hosts create type=virsh power_address=qemu+ssh://ubuntu@

Create a KVM host with overcommitted resources:

maas $PROFILE vm-hosts create type=virsh power_address=qemu+ssh://ubuntu@ \
        power_pass=example cpu_over_commit_ratio=0.3 memory_over_commit_ratio=4.6

Create a KVM host that uses a default storage pool:

maas $PROFILE vm-hosts create type=virsh power_address=qemu+ssh://ubuntu@ \
        power_pass=example default_storage_pool=pool1

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'

jq is a command-line JSON processor. More details at

Example output:


List resources of all VM hosts

maas $PROFILE vm-hosts read

A portion of the sample output:

        "id": 93,
        "capabilities": [
        "name": "civil-hermit",

List resources of a VM host

To list an individual VM host’s resources:

maas $PROFILE vm-host read $VM_HOST_ID

Update VM host configuration

Update overcommit ratios for a KVM host:

maas $PROFILE vm-host update $VM_HOST_ID power_address=qemu+ssh://ubuntu@ \
        power_pass=example cpu_over_commit_ratio=2.5 memory_over_commit_ratio=10.0

Update the default storage pool used by a KVM host:

maas $PROFILE vm-host update $VM_HOST_ID power_address=qemu+ssh://ubuntu@ \
        power_pass=example default_storage_pool=pool2

List VM host connection parameters

To list a VM host’s connection parameters:

maas $PROFILE vm-host parameters $VM_HOST_ID

Example output:

    "power_address": "",
    "power_pass": "admin",
    "power_user": "admin"

Compose VMs


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

Compose with resources specified:

maas $PROFILE vm-host compose $VM_HOST_ID $RESOURCES

Where RESOURCES is a space-separated list containing any combination of the following six items:

  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


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"


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 you want to use the first as a bootable root partition / and the second to be used as 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 this might be done.

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


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 (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 MAAS API documentation for a list of all constraint keys.

Compose and allocate a VM

In the absence of any nodes in the ‘New’ or ‘Ready’ state, if a VM host of sufficient resources is available, MAAS can automatically compose (add), commission, and acquire a VM. You can accomplish this with the allocate sub-command:

maas $PROFILE machines allocate

Note that all VM host resource parameters are available to the allocate command, so based on the example above, the following works:

maas $PROFILE machines allocate "storage=mylabel1:32(pool1),mylabel2:64(pool2)"

Once commissioned and acquired, the new machine will be ready to deploy.

The labels (i.e. mylabel1, mylabel2) in this case can be used to associate device IDs in the information MAAS dumps about the newly created VM. Try piping the output to: jq '.constraints_by_type'.

List machine parameters

MAAS VM parameters, including their resources, are listed just like any other machine:

maas $PROFILE machine read $SYSTEM_ID

Libvirt storage pools

Composing VMs with storage pool constraints

See Compose virtual machines.


Retrieve VM host storage pool information with the following command:

maas $PROFILE vm-host read $VM_HOST_ID


Machine-readable output follows:
    "used": {
        "cores": 50,
        "memory": 31744,
        "local_storage": 63110426112
    "name": "more-toad",
    "id": 5,
    "available": {
        "cores": 5,
        "memory": 4096,
        "local_storage": 153199988295
    "architectures": [],
    "cpu_over_commit_ratio": 1.0,
    "storage_pools": [
            "id": "pool_id-zvPk9C",
            "name": "name-m0M4ZR",
            "type": "lvm",
            "path": "/var/lib/name-m0M4ZR",
            "total": 47222731890,
            "used": 17226931712,
            "available": 29995800178,
            "default": true
            "id": "pool_id-qF87Ps",
            "name": "name-ZMaIta",
            "type": "lvm",
            "path": "/var/lib/name-ZMaIta",
            "total": 98566956569,
            "used": 15466229760,
            "available": 83100726809,
            "default": false
            "id": "pool_id-a6lyw5",
            "name": "name-RmDPfs",
            "type": "lvm",
            "path": "/var/lib/name-RmDPfs",
            "total": 70520725948,
            "used": 30417264640,
            "available": 40103461308,
            "default": false
    "total": {
        "cores": 55,
        "memory": 35840,
        "local_storage": 216310414407
    "tags": [],
    "type": "virsh",
    "memory_over_commit_ratio": 1.0,
    "pool": {
        "name": "default",
        "description": "Default pool",
        "id": 0,
        "resource_uri": "/MAAS/api/2.0/resourcepool/0/"
    "zone": {
        "name": "default",
        "description": "",
        "id": 1,
        "resource_uri": "/MAAS/api/2.0/zones/default/"
    "capabilities": [
    "host": {
        "system_id": null,
        "__incomplete__": true
    "default_macvlan_mode": null,
    "resource_uri": "/MAAS/api/2.0/pods/5/"

Delete a VM

maas $PROFILE machine delete $SYSTEM_ID

After you delete a machine, the machine’s resources will be available for other VMs.

Delete a VM host

maas $PROFILE vm-host delete $VM_HOST_ID

Deleting a VM host will automatically delete all machines belonging to that VM host.

It might be worth making it clear that “MyPod” needs to be changed, or excluding that and listing all pods and IDs