terra: kexec-local hangs hard on real hardware, switch docs to USB installer
Confirmed on real hardware: kexec's device_shutdown() pass runs (SCSI disks sync fine in the log) then the machine goes dark for good — journalctl --list-boots showed a ~15min gap before the next boot, a genuine hang needing a manual power cycle, not a slow jump. Near-certainly amdgpu (RX 6800 XT): discrete AMD GPUs are known to hang during kexec's device-shutdown pass with no clean handoff before the jump, same class of issue as jupiter's reboot=pci warm-reboot workaround, just fatal here instead of slow. README's terra install section now leads with the USB installer path instead (build ISO, dd to USB, rsync the repo over, disko + nixos-install locally). CLAUDE.md's gotchas list gets the same warning. installer-iso is renamed from jupiter-installer to homelab-installer since it's genuinely host-agnostic, and now ships git. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
Claude Sonnet 5
@@ -107,6 +107,14 @@ kept its ssh host key. Run it after ANY change to the kexec paths.
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- **jupiter**: `boot.kernelParams = [ "reboot=pci" ]` (warm reboot hangs on that board);
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eMMC initrd modules pinned in `configuration.nix` (generate-config misses them); the
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16TB×2 **RAID0** data lives on `/mnt/data` with `nofail`, kept OUT of disko (never wiped).
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- **terra: `./scripts/deploy kexec-local` hangs hard — do not use it there.** Confirmed
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on real hardware: kexec's `device_shutdown()` pass runs (SCSI disks sync fine in the
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log), then the machine goes dark and never comes back — `journalctl --list-boots`
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showed a ~15min gap before the next boot, i.e. a genuine hang needing a manual power
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cycle, not a slow jump. Near-certainly amdgpu (RX 6800 XT): discrete AMD GPUs are known
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to hang during kexec's device-shutdown pass with no clean handoff before the jump —
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same class of issue as jupiter's `reboot=pci` workaround, just fatal here instead of
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slow. Use the USB installer path instead (README's "First install on terra" section).
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- **disko wipes only the OS disk** named in `hosts/<h>/disk-config.nix`; data disks are
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plain `fileSystems` in `configuration.nix`.
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- `nixos-anywhere`/kexec needs a writable root; **ZimaOS root is read-only**, hence the
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@@ -84,39 +84,57 @@ an installer, partitions via disko, installs.
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Manual alternative (USB ISO): boot installer, `disko` the disk, then
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`nixos-install --flake .#jupiter`.
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## First install on terra — in-place kexec (replacing CachyOS)
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## First install on terra — USB installer (replacing CachyOS)
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terra is the desktop you're typing on, currently running CachyOS with a
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writable root — no ZimaOS-style read-only-root problem, no second machine
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needed. Everything is already prepped in this repo: real OS-disk id in
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terra is a Ryzen 9 5900X / Radeon RX 6800 XT desktop, currently running
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CachyOS. Everything is already prepped in this repo: real OS-disk id in
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`disk-config.nix`, real login pubkey in `common.nix`, terra's age recipient in
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`.sops.yaml`, its host key pre-generated at `~/.config/homelab/terra/`, and
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`secrets/terra.yaml` already holds real `darman_password` / `tailscale_authkey`
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values. Nothing to fill in — just run it.
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> ⚠️ **`./scripts/deploy kexec-local` does NOT work on terra — do not use it.**
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> Confirmed on real hardware: the jump hangs completely (kexec's own
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> `device_shutdown()` pass runs — SCSI disks sync fine — then the machine goes
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> dark and never comes back; `journalctl --list-boots` showed a **~15 minute**
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> gap before the next boot, i.e. a hard hang needing a manual power cycle, not
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> a slow jump). Near-certainly amdgpu: discrete AMD GPUs are known to hang
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> during kexec's device-shutdown pass with no clean way to hand control back
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> before the jump — same class of issue as jupiter's `reboot=pci` warm-reboot
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> workaround, just fatal here instead of merely slow. Untried mitigations
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> (unbind/`rmmod amdgpu` from a bare VT first, kernel params) might work but
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> aren't worth the risk of repeating a hard hang on a daily-driver box for a
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> one-time install — use the USB path below instead.
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> ⚠️ The OS disk (`ata-KINGSTON_SA400S37480G_50026B738072F6C6`) is WIPED. The
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> dev-data disks (`/mnt/hdd_01` ext4, `/mnt/ssd_01` LVM) and the leftover ntfs
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> disks are not in disko and are untouched — but double check with
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> `lsblk -o NAME,SERIAL,SIZE,MODEL` before proceeding if the box's disks have
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> changed since `disk-config.nix` was written.
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1. From a root shell on terra itself:
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1. Build the installer ISO and write it to a USB stick (from your laptop):
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```
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sudo ./scripts/deploy kexec-local --yes
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nix build .#nixosConfigurations.installer-iso.config.system.build.isoImage
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sudo dd if=result/iso/*.iso of=/dev/sdX bs=4M status=progress conv=fsync
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```
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Stages a RAM installer and kexecs into it. The console drops for ~1-2 min
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then comes back logged in as `nixos-installer` — same ssh host key, so
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`known_hosts` still matches if you're watching over ssh instead of the
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physical console.
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2. Still targeting terra (now `localhost`/`127.0.0.1` from the installer's own
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shell):
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2. Boot terra from the USB stick. It comes up with sshd + DHCP + your laptop
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pubkey authorized for root, hostname `homelab-installer`.
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3. From your laptop, copy the repo onto the booted installer (it doesn't have
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its own credentials for the private gitea repo, so push it over instead of
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cloning from there):
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```
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rsync -av /mnt/hdd_01/data/Dev/homelab/ root@<terra-installer-ip>:/root/homelab/
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```
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4. On terra (ssh'd in as root, or at the physical console):
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```
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cd /root/homelab
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./scripts/deploy install terra localhost
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```
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`localhost`/`127.0.0.1` skips nixos-anywhere/ssh and runs disko + `nixos-install`
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directly against `/mnt`. Ships terra's pre-generated host key so
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`/run/secrets/*` decrypts on boot #1.
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3. Reboot into NixOS. Then, same as any other host:
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`localhost`/`127.0.0.1` skips nixos-anywhere/ssh and runs disko +
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`nixos-install` directly against `/mnt`. Ships terra's pre-generated host
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key so `/run/secrets/*` decrypts on boot #1.
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5. Reboot into NixOS (remove the USB stick first). Then, same as any other
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host:
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```
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ssh darman@terra sudo -v # DO NOT SKIP — see below
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```
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@@ -163,20 +163,22 @@
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};
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# Bootable USB recovery installer with our SSH key + sshd + DHCP.
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# Reusable for any host's manual-USB install path (jupiter, terra, ...).
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# Build the ISO:
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# nix build .#nixosConfigurations.installer-iso.config.system.build.isoImage
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# dd it to a USB stick, boot the ZimaBlade from it, SSH in, ./deploy install.
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# dd it to a USB stick, boot the target from it, SSH in, ./deploy install.
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installer-iso = nixpkgs.lib.nixosSystem {
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inherit system;
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modules = [
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(nixpkgs + "/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix")
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({ ... }: {
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({ pkgs, ... }: {
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services.openssh.enable = true;
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services.openssh.settings.PermitRootLogin = "prohibit-password";
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users.users.root.openssh.authorizedKeys.keys = [
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"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGZpkPVhzi1zG5JI9hWyUgdyvNIQbp4ts4jw3idpMhhN erik@laptop"
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];
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networking.hostName = "jupiter-installer";
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networking.hostName = "homelab-installer";
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environment.systemPackages = [ pkgs.git ];
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})
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];
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};
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