ubuntu-zfs-mirror-install - SKILL.md Agent Skill

name: ubuntu-zfs-mirror-install description: Install Ubuntu Server onto a 2-disk ZFS mirror root (rpool→/) plus a striped data pool (dpool→/data) via debootstrap + ZFSBootMenu, or fall back to a plain single-disk ext4 install (GRUB-EFI) when there aren't two equal-size disks. Use when asked to install Ubuntu on ZFS, build a ZFS mirror root / rpool+dpool layout, set up root-on-ZFS with ZFSBootMenu, or do a scripted Ubuntu Server install on a UEFI x86 server with one or two SSDs/NVMes.

Ubuntu ZFS-mirror (or ext4) Server Install

Validated end-to-end (proven on an 8-GPU ASUS ESC8000-E12P). Every fix that makes the ZFS path boot hands-free and reboot-safe is baked into the scripts — see REFERENCE.md for what they are and how to recover if something's off.

Decision rule (choose the path from the disks)

Exactly two fixed disks of the SAME size → ZFS mirror (scripts/install.sh): per disk ESP | rpool-member | dpool-member; rpool mirror → /, dpool stripe → /data (no redundancy).
One disk, or two disks of different sizes → plain ext4 single-disk (scripts/install-ext4.sh): ESP | ext4 root, GRUB-EFI. (install.sh refuses unequal/single disks and points here.)

Prerequisites

Target booted into an Ubuntu Server LIVE environment (24.04+/26.04), UEFI mode (CSM off).
A root shell on it (local console, or SSH — enable ssh + set a password in the live env).
Internet reachable from the live env (debootstrap + ZFSBootMenu download).
Copy scripts/ to the target (e.g. scp -r scripts root@<live-ip>:).

Workflow

List disks: sudo bash scripts/install.sh --list — shows fixed disks with by-id paths + sizes; the live/USB medium is marked [LIVE MEDIUM, do NOT pick].

Gather settings from the user (ask; defaults in parens):

Setting	Notes
disk(s)	by-id path(s); count+size decides ZFS vs ext4
rpool size (ZFS only)	128 / 256 / 512 / 1024 GB → `RPOOL_SIZE=+128G/+256G/+512G/+1T` (default `+1T`)
admin username	default `developer`
admin password	default `passw0rd` (root gets the same)
SSH public key	optional; if set, admin is key-only (password auth off)
hostname	default `ubuntu`
timezone	optional (default `Etc/UTC`)

Run the matching installer (type ERASE when prompted, or pass --yes once the user has confirmed):

# ZFS mirror (two equal disks):
DISK1=<by-id> DISK2=<by-id> RPOOL_SIZE=+1T ADMIN_USER=developer INSTALL_PASSWORD='...' \
  SSH_AUTHORIZED_KEY='ssh-ed25519 ...' HOSTNAME=ubuntu sudo -E bash scripts/install.sh
# ext4 single disk:
DISK1=<by-id> ADMIN_USER=developer INSTALL_PASSWORD='...' HOSTNAME=ubuntu sudo -E bash scripts/install-ext4.sh

Takes ~10–20 min (debootstrap dominates). Over a flaky SSH link, run detached and tail the log: … nohup bash scripts/install.sh --yes >/root/install.log 2>&1 & then tail -f /root/install.log.

Reboot — remove the install media (or set the target disk first in UEFI boot order). It should boot ZFSBootMenu → Ubuntu (or GRUB → Ubuntu) hands-free, with / and /data (ZFS) mounted.
Validate: sudo bash scripts/validate.sh — expect pools//data ONLINE (ZFS) or / ext4, and systemctl is-system-running = running, 0 failed units.

Safety

Destructive. The installers refuse a disk that has mounted partitions (the live medium) and require typing ERASE (skip only with --yes after the user explicitly confirms the disks).
Single-NVMe failure on the ZFS layout: rpool stays bootable (degraded), dpool//data is lost (no redundancy by design).
ZFS path has no GRUB — the kernel cmdline lives in the org.zfsbootmenu:commandline ZFS property (it's set to quiet zfs_force=1; keep zfs_force=1 if you append e.g. intel_iommu=on iommu=pt).

See REFERENCE.md for the baked-in fixes, recovery steps, and hardware notes (incl. ASUS ESC8000 BMC quirks).