How to build custom images

Using packer, you can build custom, MAAS-deployable images for an ever growing list of operating systems, including:

  • RHEL 7/8/9/10
  • Rocky
  • SLES
  • Oracle Linux 8/9
  • VMware ESXi 8/9
  • Windows 2025

You can find the current list of templates here

Build Linux images

Verify requirements

You need a machine running Ubuntu 22.04+ with the ability to run KVM virtual machines. Additional packages might be necessary, and you can check your environment by running the following command in the template directory:

make check-deps

Gather components

Collect packer, its dependencies and templates, and a suitable ISO file before starting.

For most templates, Packer is not capable of automatically downloading the ISO due to licensing. In these cases the user is responsible for obtaining the required files manually and point the template to the local file.

Install Packer

Packer is the tool of choice for building custom MAAS images.

For Ubuntu 22.04+
curl -fsSL https://apt.releases.hashicorp.com/gpg | sudo apt-key add -
sudo apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main"
sudo apt-get update && sudo apt-get install packer

Install dependencies

Install dependencies required for image building:

sudo apt install qemu-utils

For Oracle Linux 8/9 and VMware ESXi, install additional dependencies:

sudo apt install libnbd-bin nbdkit fuse2fs qemu-utils

For VMware ESXi, install Python pip:

sudo apt install pip

Get Packer templates

Clone the Packer templates repository:

git clone https://github.com/canonical/packer-maas.git

Download ISO files

Download the appropriate ISO for your desired OS version and place it in the corresponding subdirectory. Please check the template’s README for the exact type of media that is required.

Customize the image

Most images can be customized by updating the auto-installer configuration file, for example a Kickstart file (RHEL based distros) or YAML file.

Refer to the template’s README for detailed customization options.

Configure a build proxy (optional)

To use a proxy during the build process:

  1. Set the HTTP proxy:

    export HTTP_PROXY=http://your-proxy-server:port

  2. Modify Kickstart Files:

    Add --proxy=$HTTP_PROXY to lines starting with url or repo.

For Oracle Linux 8/9, set the KS_PROXY variable:

export KS_PROXY=$HTTP_PROXY

Build the image

Run the following command in the appropriate subdirectory (rhel7, rhel8, centos7, ol8, ol9, vmware-esxi, etc):

make ISO=/PATH/TO/your-iso-file.iso

Upload the image to MAAS

Please refer to the template’s README file for upload instructions

Verify and log in

Deploy the image and log in to verify customizations:

OS Default Username
RHEL 7/8 cloud-user
CentOS 7 centos
Oracle Linux 8/9 cloud-user
VMware ESXi root

Build Windows images

Since Windows is a proprietary operating system, MAAS can’t download these images. You need to manually generate images to use with MAAS by using Windows ISO images. On the upside, the end result will be much simpler, since there are CLI and WebUI tools to upload a Windows image – which helps automate the process.

Verify prerequisites

To build the image:

  • A machine running Ubuntu 18.04+ with the ability to run KVM virtual machines.
  • qemu-utils, libnbd-bin, nbdkit and fuse2fs
  • qemu-system
  • ovmf
  • cloud-image-utils
  • Packer, v1.7.0 or newer
  • A copy of the packer-maas git repository:
git clone https://github.com/canonical/packer-maas.git

Note that Ubuntu 22.04+ is required to build Windows 11 images due to swtpm (Software TPM) package requirements.

Supported Microsoft Windows versions

This process has been build and deployment tested with the following versions of Microsoft Windows:

  • Windows Server 2025
  • Windows Server 2022
  • Windows Server 2019
  • Windows Server 2016
  • Windows 10 PRO+
  • Windows 11 PRO+

To deploy the image:

Gather components

Collect an ISO image and a template before trying to build a Windows image.

Get the windows.pkr.hcl Template

This template builds a dd.tgz MAAS image from an official Microsoft Windows ISO/VHDX.
This process also installs the latest VirtIO drivers as well as Cloudbase-init.

Obtain Microsoft Windows ISO images

You can obtains Microsoft Windows Evaluation ISO/VHDX images from the following links:

Build the image

The build the image you give the template a script which has all the customization:

sudo make windows ISO=<path-to-iso> VERSION=<windows-version>

Example:

sudo make ISO=/mnt/iso/Windows_Server_2025_SERVER_EVAL_x64FRE_en-us.iso VERSION=2025

Adjust makefile parameters

EDIT

The edition of a targeted ISO image. It defaults to PRO for Microsoft Windows 10/11 and SERVERSTANDARD for Microsoft Windows Servers. Many Microsoft Windows Server ISO images do contain multiple editions and this parameter is useful to build a particular edition such as Standard or Datacenter etc.

HEADLESS

Whether VNC viewer should not be launched. Default is set to false. This is useful when building images on machines that do not have graphical libraries such as SDL/GTK installed. Headless mode does include an open VNC port to monitor the build process if needed.

ISO

Path to Microsoft Windows ISO image used to build the MAAS image.

PACKER_LOG

Enable (1) or Disable (0) verbose packer logs. The default value is set to 0.

PKEY

User supplied Microsoft Windows Product Key. When using KMS, you can obtain the activation keys from the link below:

Please note that PKEY is an optional parameter but it might be required during the build time depending on the type of ISO being used. Evaluation series ISO images usually do not require a product key to proceed, however this is not true with Enterprise and Retail ISO images.

TIMEOUT

Defaults to 1h. Supports variables in h (hour) and m (Minutes).

VHDX

Path to Microsoft Windows VHDX image used to build the image.

VERSION

Specify the Microsoft Windows Version. Example inputs include: 2025, 2022, 2019, 2016, 10 and 11. Currently defaults to 2022.

Upload Windows images to MAAS

Use MAAS CLI to upload the image:

maas admin boot-resources create \
    name='windows/windows-server' \
    title='Windows Server' \
    architecture='amd64/generic' \
    filetype='ddtgz' \
    content@=windows-server-amd64-root-dd.gz

Last updated a month ago.

Help improve this document in the forum.