Ubuntu Autoinstall Scripts

By Andy Sayler
July 2026

• Ubuntu Server Version: 26.04 (previously tested with 20.04, 22.04)
• Default Username: setup
• Default Password: setup
• Default Encryption Key: setup

Contents

• user-data-base: Basic autoinstall file that configures a server for SSH and used the default partition scheme.
• user-data-storage-btrfs: Builds on user-data-basic to define a custom partition scheme for the first NVMe device on the system using the btrfa filesystem.
• user-data-encrypted-btrfs: Builds on user-data-storage to add LUKS full disk encryption to the partition scheme. NOTE: Please change the LUKS password after first boot. Default LUKS password is above.
• user-data-encrypted-ext4: Same as the previous version, but using ext4 instead of btrfs. NOTE: Please change the LUKS password after first boot. Default LUKS password is above.
• user-data-encrypted-zfs-auto: Alternate to user-data-encrypted-btrfs using the guided ZFS layout with native ZFS encryption instead of manual LUKS partitioning. NOTE: Please change the encryption passphrase after first boot. Default passphrase is above. (UNTESTED)
• user-data-encrypted-zfs-manual: Same encrypted-ZFS scheme as the previous version, but built from low-level zpool/zfs storage actions on a fixed partition layout instead of the guided layout. NOTE: Please change the encryption passphrase after first boot. Default passphrase is above. (UNTESTED)

Build

1. Customize appropriate user-data-XXXX file as needed
2. Build cloudinit iso: cloud-localds ./autoinstall.iso ./user-data-XXXX ./meta-data
3. Mount both autoinstall.iso and Ubuntu 26.04 server.iso (I tend to use the IPMI console to do this on headless servers, but doing it via VM commands or actual media on a physical server should all work as well.)
4. Boot system to Ubuntu server installer and select yes when prompted to start autoinstall
5. Profit

Notes

• Generate Crypted Password: openssl passwd -6

Validation

Every user-data-* file is checked on push/PR by a GitHub Actions workflow that runs Subiquity's own validate-autoinstall-user-data.py against it (see the autoinstall validation howto). This is not a local pre-commit check since the validator needs a full Subiquity checkout and sudo apt-get install-ed dependencies.

References

• https://ubuntu.com/server/docs/install/autoinstall
• https://ubuntu.com/server/docs/install/autoinstall-reference
• https://curtin.readthedocs.io/en/latest/topics/storage.html
• https://canonical-subiquity.readthedocs-hosted.com/en/latest/howto/autoinstall-validation.html