Step-by-Step Guide: Creating an Ubuntu Autoinstall ISO with Cloud-init

Automating the installation process is essential for streamlining system deployment, especially in environments that require consistent setups across multiple machines.

Ubuntu’s Autoinstall feature, combined with Cloud-init, provides a powerful way to preconfigure installations with minimal effort. Whether you’re setting up servers for a data center or configuring multiple workstations, a custom Autoinstall ISO can save hours of repetitive work. 

This guide will help you create a bootable ISO tailored to your specific needs, ensuring a smooth and efficient installation process every time.

Overview

Creating a custom Ubuntu autoinstall ISO simplifies and automates OS deployment, saving time and ensuring consistency. This guide walks you through building an Ubuntu autoinstall ISO using Cloud-init for automatic configuration. The result is a bootable ISO that requires minimal manual intervention during installation.

Steps to Create an Autoinstall ISO

Creating a custom Ubuntu Autoinstall ISO involves several steps. 

Follow this structured process to ensure a smooth setup:

Step 0 - Requirements and Preparing the “user-data” YAML File(s)

Before starting, ensure you have:

• A system running Ubuntu or any Linux distribution.
• A clean Ubuntu ISO image (20.04 or later).
• Packages like xorriso, mkisofs, and cloud-init.

Create a user-data YAML file, which contains the automation script for your installation. This file will define users, partitions, packages, and other configurations.

Step 1 - Set Up a Working Directory and Obtain a Clean Base ISO Image

Start by setting up a working directory:

   mkdir ~/autoinstall-iso && cd ~/autoinstall-iso 

Download the official Ubuntu ISO:

   wget https://releases.ubuntu.com/22.04/ubuntu-22.04-live-server-amd64.iso 

Step 2 - Extract the Contents of the Install ISO

Extract the ISO contents to your working directory:

7z x ubuntu-22.04-live-server-amd64.iso -oiso_extracted/ 

Ensure the contents are correctly extracted by navigating into the iso_extracted directory.

Step 3 - Modify the GRUB and ISOLINUX Configuration Files

Edit the bootloader to enable automated installation.

• Modify GRUB: Open iso_extracted/boot/grub/grub.cfg and append the following to the linux line under the default menu entry:

autoinstall ds=nocloud\;s=/cdrom/ 

• Modify ISOLINUX: Edit iso_extracted/isolinux/txt.cfg similary way by adding:

autoinstall ds=nocloud\;s=/cdrom/

Step 4 - Integrate Your Custom “user-data” YAML File(s) into the ISO

Create a nocloud directory inside iso_extracted:

   mkdir -p iso_extracted/nocloud/ 

Place your user-data and meta-data files into this directory. For basic usage, meta-data can be an empty file:

   touch iso_extracted/nocloud/meta-data 

   mv user-data iso_extracted/nocloud/ 

Step 5 - Rebuild the Autoinstall ISO

Repack the modified ISO using the following command:

xorriso -as mkisofs -r -V "Autoinstall Ubuntu" \ 

   -o ~/autoinstall-ubuntu-22.04.iso \ 

   -J -l -cache-inodes -b isolinux/isolinux.bin \ 

   -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 \ 

   -boot-info-table iso_extracted/ 

This command generates a bootable ISO with all your custom configurations.

Example of a “user-data” YAML File

Here’s a simple example of a user-data file:

#cloud-config 

autoinstall: 

version: 1 

identity: 

hostname: ubuntu-server 

username: admin 

password: $6$hashed_password 

ssh: 

install-server: true 

storage: 

layout: 

name: lvm 

packages: 

- vim 

- curl 

Closing Remarks

With this guide, you’ve created a custom Ubuntu autoinstall ISO using Cloud-init. This approach simplifies repetitive installations and ensures consistency across deployments. Test your ISO in a virtual machine to verify its behavior before large-scale use.