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nixos/scripts/prepare-host-key.sh
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beatzaplentyandClaude Sonnet 5 2858891c20
Check NixOS configurations / eval-hosts (push) Failing after 10m48s
Add sync-host-keys.sh and create-proxmox-resource.sh
sync-host-keys.sh: generates/registers SSH host keys and their
.sops.yaml/secrets/*.yaml recipients for flake targets, idempotently.
--all, <target>, --remove, --regenerate-all-keys, all with --dry-run
(verified zero-side-effect via a sandboxed git-status check across every
mode). Only ever touches anchors with a corresponding host-keys/ file --
&admin and any hand-registered real-host anchor are never listed,
removed, or regenerated. Supersedes running prepare-host-key.sh one host
at a time for any target that already has a flake entry.

create-proxmox-resource.sh: builds a lxc-*/proxmox-* target's
tarball/disk image and creates it on a real Proxmox node, or reconfigures
an existing resource's cores/memory/disk (--modify, always requires
typing the VMID back to confirm). Refuses to create a new resource for a
VMID that already exists, and refuses to duplicate a host identity that
already has a real deployment elsewhere (variables.nix's new
deployedTargets, checked by hostName so it also catches cross-platform
duplicates) unless --allow-duplicate-host is passed. --dry-run throughout.

scripts/env.sh centralizes the Proxmox connection config both scripts
(and future ones) share. Also fixes an unrelated gap found along the way:
proxmox-* Disko image builds write their .raw file straight into the
repo root, and .gitignore never covered it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01La55Nsss8jZ7ZuzUV9mfot
2026-07-20 10:31:06 +10:00

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#!/usr/bin/env bash
# Generates a new machine's SSH host key by an arbitrary name, before it
# necessarily has a flake target yet -- prints the .sops.yaml snippet to
# add by hand. For any host that already has a flake target,
# scripts/sync-host-keys.sh <target> does this same job plus the
# .sops.yaml/key_groups registration and re-encryption automatically; use
# this script only to pre-generate a key ahead of adding the flake target
# itself.
#
# Why a host key is needed at all: sops-nix derives each host's decryption key from
# its own /etc/ssh/ssh_host_ed25519_key at *activation* time, but that
# activation runs before systemd would otherwise generate this key on
# first boot (sshd-keygen is a normal systemd service gated behind
# multi-user.target; activation scripts run earlier than that). Without
# pre-seeding, secrets — including the root/nixos login password — fail
# to decrypt on the machine's very first boot.
#
# This script only touches your admin workstation and this repo's
# .sops.yaml (it never contacts the target machine). Run it, follow the
# printed next steps, then use the resulting key with the auto-install.sh
# prompt (see modules/installer/common.nix) when you actually install the
# new machine.
set -euo pipefail
repo_root="$(cd "$(dirname "$0")/.." && pwd)"
hostname="${1:?usage: scripts/prepare-host-key.sh <hostname>}"
sops_yaml="${repo_root}/.sops.yaml"
if [[ ! -f "$sops_yaml" ]]; then
echo "ERROR: $sops_yaml not found — is this script still under nixos/scripts/?" >&2
exit 1
fi
keydir="${repo_root}/host-keys"
mkdir -p "$keydir"
keyfile="${keydir}/${hostname}_ssh_host_ed25519_key"
if [[ -f "$keyfile" ]]; then
echo "ERROR: $keyfile already exists. Remove it first if you want to regenerate." >&2
exit 1
fi
nix-shell -p openssh --run "ssh-keygen -t ed25519 -N '' -C '${hostname}' -f '${keyfile}'" >/dev/null
age_pub="$(nix-shell -p ssh-to-age --run "ssh-to-age -i '${keyfile}.pub'")"
cat <<EOF
Generated: ${keyfile}(.pub)
=== 1. Add this line under keys: in ${sops_yaml} ===
- &${hostname} ${age_pub}
=== 2. Add *${hostname} to whichever creation_rules key_groups this host needs ===
(e.g. secrets/common.yaml always; add a per-host secrets/${hostname}.yaml
block too if this host will get its own secrets, same pattern as
nix-cache/server.)
=== 3. Re-encrypt every secrets file you just added it to ===
nix-shell -p sops --run 'sops updatekeys ${repo_root}/secrets/common.yaml'
=== 4. Commit + push this repo so the flake build picks up the new recipient ===
=== 5. Get the key onto the installer, one of two ways ===
a) Rebuild the installer image with all host-keys/ baked in (see
docs/auto-installer.md):
NIXOS_HOST_KEYS_DIR="${keydir}" nix build .#iso --impure
(or .#pxe — --impure is required since host-keys/ is gitignored and
flakes can't see it otherwise)
b) Or, for an image already built without keys, scp it in after boot:
scp ${keyfile}{,.pub} root@<target-ip>:/root/host-keys/
Then continue with /etc/auto-install.sh as normal — it checks
/etc/host-keys (baked in) before /root/host-keys (scp'd) and installs
whichever it finds before running nixos-install.
EOF