Cloud Init ISO

Many premade cloud images (e.g. Fedora Cloud, Ubuntu Cloud) use some form of cloud-init to set instance/user metadata, such as hostnames and SSH keys. This works well when used in a cloud infrastructure such as EC2 or OpenStack that can seed this data, but not so well when used for local VMs, or an out-of-the-box XenServer installation.

However, cloud-init supports an CD/ISO datasource, which can be loaded whether running the machine locally in KVM, VirtualBox, or on a XenServer host.

This repository and guide aims to make this task a lot easier by pre-seeding a template and script. It draws heavily on existing resources (2, 3).

Dependencies

You need one of xorriso (xorrisofs), mkisofs, or genisoimage installed. The build script is plain POSIX sh, so bash is not required.

• Fedora, RHEL 8+ and rebuilds (AlmaLinux, Rocky, Oracle Linux): sudo dnf install xorriso. On RHEL it comes from the AppStream repository (it is not in the UBI container repos). genisoimage is no longer shipped in RHEL 10.
• Ubuntu, Debian, and derivatives: sudo apt install xorriso.
• Alpine: apk add xorriso (or apk add cdrkit for mkisofs).
• macOS: brew install xorriso.

Usage

1. Clone this repository. (optional: maybe create and checkout your own branch?)
2. Modify the meta-data YAML file to specify your instance-id and local-hostname.
3. Modify the user-data YAML file -- according to cloud-config syntax -- to specify a password and/or SSH keys. The cloud image determines the default user's login name, but you can override that according to the cloud-config documentation.
4. (optional) Commit your changes in git. This helps the build script name your ISO.
5. Build the ISO using ./build.sh. You can either specify an output filename as the first parameter (e.g. ./build.sh output-file.iso), or you can let the script decide on the filename. If you are working inside a git repository, the build script should name your file after the branch and short commit hash, such as frost-init-20141228.dd648b2e.iso. If the output file already exists, the script stops without touching it; pass --overwrite (or -f/--force) to replace it, e.g. ./build.sh --overwrite output-file.iso.
6. If everything went well, attach the ISO file to your VM by methods conventional to your virtualization hypervisor.
7. Boot the VM!

Guest compatibility notes

• Fedora Cloud, RHEL/AlmaLinux/Rocky, Ubuntu, and Debian generic/genericcloud images all run cloud-init, which picks up the cidata ISO automatically. (Debian's nocloud images do not include cloud-init, despite the name.)
• Alpine's official cloud images default to tiny-cloud rather than cloud-init. It reads this ISO and applies local-hostname and ssh_authorized_keys, but ignores password, chpasswd, and ssh_pwauth. Use SSH keys, or the cloudinit variant of the Alpine image, if you need password login.

License

Some parts of this project are clearly not original. However, the bash script and any exemplary portions of the config files are hereby licensed under the MIT License; see LICENSE.