Create a VM with Incus

Creating a basic Virtual Machine with Incus is a simple command via the terminal.

Create VM using the terminal

Using a user that is part of the incus-admin group execute the following command to get a basic Ubuntu 22.04 VM:

incus launch images:ubuntu/22.04 vm-name --vm --type c1-m4

WTF do the flags means?!

• --vm Tells Incus we want a Virtual Machine and not a container
• --type Specifies the core count (cX) and amount of memory (mX). You can also use AWS image sizes e.g. t1.mirco

Disk Size

By default the VM will have a very small disk, because of this I tend to customise the size by modifying the above command with the --device command like so:

incus launch images:ubuntu/22.04 vm-name --vm --type c1-m4 --device root,size=30GiB

This will give me a 30 GiB root partition.

Cloud Init

One of the benefits of LXD/Incus is the ability to use cloud-init.

This allows VMs to be configured on boot to add things like:

• Add Users
• Packages
• Files

With Incus I tend to always use a base cloud-init profile to add a user, setup sudo and ensure OpenSSH server is installed.

Create a cloud-init profile

Creating a cloud-init profile is simple, at it's core cloud-init uses a YAML file.

My cloud-config.yml looks similar to this, obviously changed in places for security purposes:

cloud-config.yml

#cloud-config
package-update: true # Run a package update
packages: # The packages you want to install
  - sudo
  - openssh-server
users:
  - default # Default user, worth keeping unless you know what you are doing
  - name: andy # Username
    shell: /bin/bash # Default shell
    lock_passwd: false # Setting this to true means you can only SSH using public, private key
    passwd: $6$rounds=4096$dtOF9U0rJEXp5sog$Z2So4IjqhC2qOoJQ1VCTeZh6QL5pkogbtHN/DMHJ5jsTgSigIdY5ivJzvi77VdFZotXTVma28jgOq2OSncBkh0 # password01 - Yes totally my real password ;)
    ssh_authorized_keys:
      - ssh-ed25519 SomeRandomNumbersAndLetters # Public SSH key
    groups:
      - sudo # Add the user to the sudo group
    sudo: ALL=(ALL:ALL) ALL # Sudo config for the user, this means password is required to elevate

Once you have created your version it is worth validating it by using the cloud-init schema command:

sudo cloud-init schema --config-file cloud-config.yml

How do I create a password hash?

On a Linux machine use the tool mkpasswd¹ like so:

mkpasswd --method=SHA-512 --rounds=4096

OK so how do I create a VM using this cloud-init file?

By doing two modifications to the command above you can launch a VM that is configured using cloud-int.

Firstly we need to use a different image as the one above doesn't have cloud-init support. This isn't too difficult as most of the linuxcontainer images have a cloud variant that can be used by appending /cloud to the image, for example:

images:ubuntu/22.04 has no cloud-init images:ubuntu/22.04/cloud has cloud-init

We also need to specify the cloud-init file by passing the --config flag:

incus launch images:ubuntu/22.04 vm-name --vm --type c1-m4 --config=user.user-data="$(cat cloud-config.yml)"

Connecting to VM

There are three options to connect to this VM:

• Incus exec
• SSH
• Console

Incus Exec

If you haven't enabled SSH you can connect to the VM using the Incus command:

incus exec vm-name bash

This will drop you into the machine as the root user.

SSH

If you have installed OpenSSH server and added a user you can connect to the VM using SSH.

First find the IP Address of the Virtual Machine. The easiest way to do this is using the command:

incus list

You'll get an output similar to this:

+---------------+---------+-------------------------+------------------------------------------------+-----------------+-----------+
|     NAME      |  STATE  |          IPV4           |                      IPV6                      |      TYPE       | SNAPSHOTS |
+---------------+---------+-------------------------+------------------------------------------------+-----------------+-----------+
| test-instance | RUNNING | 192.168.40.217 (enp5s0) | fd42:4a06:cc15:9d0:216:3eff:feab:77db (enp5s0) | VIRTUAL-MACHINE | 0         |
+---------------+---------+-------------------------+------------------------------------------------+-----------------+-----------+

Then you can connect over SSH using the IPV4 address.

Console Access

It's also possible to connect over console if you have a user setup on the VM. This can be accessed with the command:

incus console vm-name

You'll then be dropped into a console, to exit the console use the key combination Ctrl+a q.

Footnotes

1. You may need to install this tool, on Ubuntu it wasn't installed by default and required the install of whois (apt install whois) ↩