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Give linode-* hosts a real Disko config, simplify auto-install.sh

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Linode provisions and sizes /dev/sda (root) and /dev/sdb (swap) itself
as whole, unpartitioned block devices before the OS ever boots.
modules/disko/linode.nix declares them with destroy = false (skips
Disko's wipe stage for these disks entirely) and a bare filesystem/swap
content type matching that existing layout, so re-running it against an
already-provisioned disk only mkfs/mkswaps if blkid shows it isn't
formatted yet -- never repartitions or destroys data.

With every host reachable through the installer menu now carrying a
Disko config, auto-install.sh no longer needs to probe the flake and
branch between `disko --mode destroy,format,mount` and a bind-mount
fallback -- it just always runs Disko.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01La55Nsss8jZ7ZuzUV9mfot
This commit is contained in:
beatzaplenty
2026-07-20 08:04:34 +10:00
co-authored by Claude Sonnet 5
parent 2aa625d566
commit a351cbcf80
6 changed files with 70 additions and 29 deletions
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README.md
+4 -1
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@@ -93,7 +93,10 @@ Three different paths depending on target, none of them involving a manual
`nixos-rebuild switch` from this repo:
- Most hosts: boot the auto-installer, pick the target from its menu — see
`docs/auto-installer.md`.
`docs/auto-installer.md`. Every menu target has a Disko config the
installer formats unconditionally (`docs/auto-installer.md`'s "Storage"
section covers how this stays non-destructive for `linode-*`, whose disks
Linode itself provisions ahead of time).
- `lxc-*` targets: not installed at all — build a ready-to-run container
tarball and `pct restore` it directly. `docs/auto-installer.md` covers why
(and the installer's menu excludes them for the same reason).
docs/auto-installer.md
+19 -5
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@@ -126,10 +126,24 @@ next, where you can `scp` a key in after boot, same as before this migration.
## Storage
Disk partitioning is handled by Disko — the installer has no hardcoded
`parted`/`mkfs`/`mkswap`/`mount` commands. Each host defines its own layout
via `disko.devices`; a host without one is installed in place via bind-mount
(this is how every LXC container target works, since they have no raw block
device to partition).
`parted`/`mkfs`/`mkswap`/`mount` commands, and `auto-install.sh` runs
`disko --mode destroy,format,mount` unconditionally, no branching on whether
the target has a Disko config. Every host reachable through this menu has
one:
- `proxmox-*` (`modules/disko/proxmox.nix`): a real GPT partition table
(ESP + swap + root) on `/dev/sda`.
- `linode-*` (`modules/disko/linode.nix`): Linode provisions and sizes
`/dev/sda`/`/dev/sdb` itself as whole, unpartitioned block devices before
the OS ever boots, so this declares them with `destroy = false` (skips
disko's wipe stage for these disks entirely — see the option's own docs)
and a bare `filesystem`/`swap` content type with no partition table, and
the format step it does run only calls `mkfs`/`mkswap` if `blkid` shows
the device isn't already formatted — a re-run against an
already-provisioned Linode disk is a no-op, not a wipe.
`lxc-*` is the only category without one — it's excluded from this menu
entirely (see "LXC hosts" above), so it never reaches this code path.
## Installer process
@@ -138,7 +152,7 @@ device to partition).
1. Queries `nixosConfigurations` from this flake over the network (`git+https://<lanDomain>/beatzaplenty/nixos.git`) — this happens at *install* time, not build time, so a generic installer image always sees whatever hosts are currently committed, without needing a rebuild.
2. Presents them as a menu; confirms the choice.
3. Skips the `nix-cache` substituter when installing a `nix-cache` host itself (consistent with that host's own runtime config).
4. Runs `disko --mode destroy,format,mount` if the target has a Disko config, otherwise bind-mounts `/` onto `/mnt`.
4. Runs `disko --mode destroy,format,mount` (see "Storage" above — every host reachable through this menu has a Disko config, so this is unconditional).
5. Installs the target's SSH host key from `/etc/host-keys` or `/root/host-keys` (see "Host keys" above).
6. Runs `nixos-install --flake <url>#<choice> --no-root-password`.
7. Cleans up and reboots.
modules/disko/linode.nix
+35
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@@ -0,0 +1,35 @@
_:
{
# Linode provisions and sizes these disks itself (via the Linode
# dashboard/API) before the OS ever boots, and presents them as whole,
# unpartitioned block devices — /dev/sda is the root filesystem directly,
# /dev/sdb is swap directly, no partition table on either. Nothing here
# should ever repartition or resize them:
# - `destroy = false` skips each disk entirely during disko's destroy
# stage (see disko's disk.destroy option) — no wipefs, ever.
# - the filesystem content type's own create step only runs mkfs if the
# device isn't already formatted (checked via `blkid`), so re-running
# this against an already-provisioned Linode disk is a no-op.
disko.devices.disk = {
main = {
device = "/dev/sda";
destroy = false;
content = {
type = "filesystem";
format = "ext4";
mountpoint = "/";
};
};
swap = {
device = "/dev/sdb";
destroy = false;
content = {
type = "swap";
};
};
};
}
modules/hardware-configuration/vm/linode.nix
+5 -8
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@@ -33,14 +33,11 @@
};
};
fileSystems."/" =
{
device = "/dev/sda";
fsType = "ext4";
};
swapDevices =
[{ device = "/dev/sdb"; }];
# fileSystems."/" and swapDevices are now owned by disko
# (../disko/linode.nix, imported from ../platforms/linode.nix) — same
# /dev/sda root + /dev/sdb swap layout, declared there instead so disko's
# (idempotent, non-destructive — see that file) format/mount scripts stay
# in sync with what NixOS actually mounts.
nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
}
modules/installer/common.nix
+6 -15
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@@ -119,21 +119,12 @@
nix_extra_opts+=(--option substituters "https://cache.nixos.org/")
fi
if nix eval --refresh --json --extra-experimental-features "flakes nix-command" "''${nix_extra_opts[@]}" "''${FLAKE_BASE_URL}#nixosConfigurations.''${choice}.config.disko.devices.disk.main.device" >/dev/null 2>&1; then
disko --mode destroy,format,mount \
--flake "''${FLAKE_BASE_URL}#''${choice}" "''${nix_extra_opts[@]}" --yes-wipe-all-disks
else
# No raw disk to partition — true for every LXC container, which has
# no block device visible from inside it, only its already-mounted
# root filesystem. nixos-install defaults to installing into /mnt; if
# nothing points /mnt at the real root, the new system gets built and
# written to a disconnected empty directory, never actually becomes
# bootable, and the container silently keeps running this installer
# environment forever. Bind-mount / onto /mnt so the install actually
# lands on the filesystem this container boots from.
echo "Selected host has no Disko configuration — installing in place via bind mount."
mount --bind / /mnt
fi
# Every host reachable through this menu has a Disko config (lxc-*
# is filtered out above, and is the only category that doesn't —
# see docs/auto-installer.md), so this can run unconditionally: no
# need to probe the flake first and branch on whether Disko applies.
disko --mode destroy,format,mount \
--flake "''${FLAKE_BASE_URL}#''${choice}" "''${nix_extra_opts[@]}" --yes-wipe-all-disks
# sops-nix derives this host's decryption key from its own SSH host key
# at *activation* time, which runs before systemd would otherwise
modules/platforms/linode.nix
+1
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@@ -3,6 +3,7 @@
{
imports = [
../hardware-configuration/vm/linode.nix
../disko/linode.nix
];
networking = {