feat(pfi-gx10): register the ASUS Ascent GX10 and convert it to headless

NVIDIA GB10, aarch64, 121 GB unified, sm_121. Ships booting to graphical.target
with GDM and GNOME Remote Desktop running.

playbooks/gx10-headless.yaml sets multi-user.target, stops gnome-remote-desktop,
masks the sleep/suspend/hibernate targets, makes logind ignore lid and idle, and
adds sshd keepalives so a stalled link does not kill a long-running job.

Two things learned the hard way and recorded in the playbook:

- gdm is a STATIC unit on Ubuntu, pulled in by display-manager.service and never
  'enabled'. A guard of  always skips, and a verify
  written the same way passes while the desktop is still running. Both now test
  is-active. The first run reported six green verifies having not stopped gdm.
- elway's --sudo applies only to ad-hoc --shell/--upload. Playbook steps run as
  the connecting user and must carry their own sudo; connect as infra-ops.

The playbook refuses to stop the display manager while a seat session is held,
overridable with --var force_dm_stop=true. Networking is deliberately out of
scope: the box is on a desk on Wi-Fi with a temporary DHCP lease and no ethernet
carrier, and belongs to the rack-install change.

playbooks/gx10-headless.yaml

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+# pfi-gx10 — convert an ASUS Ascent GX10 (NVIDIA GB10, aarch64) from its
+# out-of-box desktop configuration to headless server operation.
+#
+#   scripts/elway infra-ops@10.100.10.226 --playbook playbooks/gx10-headless.yaml
+#
+# CONNECT AS infra-ops. `--sudo` only applies to ad-hoc --shell/--upload, so
+# playbook steps run as the connecting user and carry their own sudo. lkraven
+# needs a password for sudo on this box; infra-ops is NOPASSWD.
+#
+# The box ships booting to graphical.target with GDM and GNOME Remote Desktop
+# running. That is correct for a desk appliance and wrong for a rack node: a
+# display manager holds a GPU context, and a laptop-derived power profile will
+# suspend a machine that is meant to answer at 3am.
+#
+# OUT OF SCOPE — DELIBERATELY:
+#   Networking. As of 2026-09-01 this box sits on a desk on Wi-Fi with a
+#   temporary DHCP lease (10.100.10.226) and NO ethernet carrier (enP7s7
+#   carrier=0). Static addressing, VLAN placement and DNS all belong to the
+#   rack-install change, not to this one. Configuring an address that is about
+#   to be wrong is worse than leaving it on DHCP.
+#
+# REVERSIBLE. Every step here undoes with:
+#   systemctl set-default graphical.target
+#   systemctl unmask sleep.target suspend.target hibernate.target
+#   systemctl enable --now gdm
+#
+# Idempotent: a second run should report ok/skipped throughout.
+
+vars:
+  fqdn_hostname: pfi-gx10
+  # Stop the display manager even if someone is logged in at the console.
+  #   scripts/elway infra-ops@<host> -p ... --var force_dm_stop=true
+  force_dm_stop: "false"
+
+steps:
+  # ---------------------------------------------------------------------------
+  # Identity
+  # ---------------------------------------------------------------------------
+  - name: Set the static hostname to match the transient one
+    # Ships with static=gx10-a745 but transient=pfi-gx10, so `hostname` and
+    # `hostnamectl` disagree. Anything keying on one of them picks the wrong
+    # name half the time. pfi-gx10 is the fleet-convention name.
+    shell: sudo hostnamectl set-hostname {{ fqdn_hostname }}
+    when: "test \"$(hostnamectl --static)\" != '{{ fqdn_hostname }}'"
+
+  # ---------------------------------------------------------------------------
+  # Stop booting into a desktop
+  # ---------------------------------------------------------------------------
+  - name: Default boot target -> multi-user
+    shell: sudo systemctl set-default multi-user.target
+    when: "test \"$(systemctl get-default)\" != 'multi-user.target'"
+
+  - name: Stop GDM
+    # ⚠ GUARD ON is-active, NOT is-enabled. Ubuntu ships gdm as a STATIC unit —
+    # it is pulled in by display-manager.service and is never "enabled". A
+    # `is-enabled | grep enabled` guard therefore always skips, and a verify
+    # written the same way passes while gdm is still running. Cost one green
+    # run that had not done the thing. (2026-09-01)
+    #
+    # GNOME stays INSTALLED, only stopped: removing it frees little on a 916G
+    # disk and makes this hard to walk back from a serial console.
+    #
+    # Will NOT run while someone holds a seat session, unless force_dm_stop=true.
+    # Yanking the display out from under a person at the machine is not a thing
+    # automation should decide to do.
+    shell: sudo systemctl stop gdm
+    when: "systemctl is-active --quiet gdm && { [ '{{ force_dm_stop }}' = 'true' ] || ! loginctl list-sessions --no-legend 2>/dev/null | grep -qE ' seat[0-9]+ '; }"
+
+  - name: Stop and disable GNOME Remote Desktop
+    # Needs a graphical session to be useful; with GDM gone it is a listener
+    # with nothing behind it.
+    shell: sudo systemctl disable --now gnome-remote-desktop
+    when: "systemctl is-enabled gnome-remote-desktop 2>/dev/null | grep -q enabled"
+
+  # ---------------------------------------------------------------------------
+  # A server must never sleep
+  # ---------------------------------------------------------------------------
+  - name: Mask sleep / suspend / hibernate / hybrid-sleep
+    # Masking, not disabling. These are `static` units pulled in by logind and
+    # by desktop power policy; disable does not stick, mask does.
+    shell: sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target
+    when: "! systemctl is-enabled sleep.target 2>/dev/null | grep -q masked"
+
+  - name: logind must ignore lid and idle
+    shell: |
+      sudo install -d /etc/systemd/logind.conf.d
+      sudo tee /etc/systemd/logind.conf.d/10-headless.conf >/dev/null <<'EOF'
+      [Login]
+      HandleLidSwitch=ignore
+      HandleLidSwitchExternalPower=ignore
+      HandleLidSwitchDocked=ignore
+      IdleAction=ignore
+      EOF
+    creates: /etc/systemd/logind.conf.d/10-headless.conf
+
+  # ---------------------------------------------------------------------------
+  # Keep long jobs alive across a dropped SSH session
+  # ---------------------------------------------------------------------------
+  - name: sshd keepalives so a NAT/Wi-Fi stall does not kill a running job
+    shell: |
+      sudo install -d /etc/ssh/sshd_config.d
+      sudo tee /etc/ssh/sshd_config.d/10-fleet.conf >/dev/null <<'EOF'
+      ClientAliveInterval 60
+      ClientAliveCountMax 10
+      TCPKeepAlive yes
+      EOF
+      sudo sshd -t
+      sudo systemctl reload ssh 2>/dev/null || sudo systemctl reload sshd
+    creates: /etc/ssh/sshd_config.d/10-fleet.conf
+
+verify:
+  - name: Boots to multi-user, not graphical
+    shell: test "$(systemctl get-default)" = "multi-user.target"
+    changed_when: "false"
+
+  - name: Will boot headless — default target is multi-user
+    # The DURABLE requirement, true across reboots regardless of what is
+    # running right now.
+    shell: test "$(systemctl get-default)" = "multi-user.target"
+    changed_when: "false"
+
+  - name: GDM is not running
+    # is-ACTIVE. Expected to FAIL while someone holds a console session and
+    # force_dm_stop is false — that is an honest red, not a broken playbook.
+    # A reboot (or the rack install) resolves it.
+    shell: "! systemctl is-active --quiet gdm"
+    changed_when: "false"
+
+  - name: Sleep targets are masked
+    shell: systemctl is-enabled sleep.target 2>/dev/null | grep -q masked
+    changed_when: "false"
+
+  - name: Static hostname is correct
+    shell: test "$(hostnamectl --static)" = "{{ fqdn_hostname }}"
+    changed_when: "false"
+
+  - name: GPU still enumerates after the desktop stack stopped
+    # The point of the exercise. If disabling GDM cost us the GPU, this catches
+    # it here rather than the next time someone tries to load a model.
+    shell: nvidia-smi --query-gpu=name,compute_cap --format=csv,noheader | grep -q GB10
+    changed_when: "false"
+
+  - name: sshd config still parses
+    shell: sudo sshd -t
+    changed_when: "false"

servers/pfi-gx10/README.md

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+# pfi-gx10 — ASUS Ascent GX10 (NVIDIA GB10)
+
+Grace-Blackwell desktop supercomputer. Registered 2026-09-01.
+
+| | |
+|---|---|
+| GPU | **NVIDIA GB10**, driver 580.173.02, **compute capability 12.1 (`sm_121`)** |
+| CPU | 20 cores, **aarch64** |
+| Memory | **121 GB unified** (CPU and GPU share it — not 121 GB *plus* VRAM) |
+| Storage | 916 GB NVMe, 6% used |
+| Kernel | 6.17.0-1031-nvidia |
+| Hostname | `pfi-gx10` (shipped with static `gx10-a745`, corrected) |
+
+## ⚠ The address in `ssh-target` is TEMPORARY
+
+As of 2026-09-01 this box is **on a desk, on Wi-Fi**, holding a DHCP lease at
+`10.100.10.226` on `nh3-userland` (VLAN 10). Ethernet `enP7s7` has no carrier.
+
+It is going into the rack later. At that point it needs a wired link, a static
+address, a decision about VLAN placement (a compute node arguably belongs on
+`nh3-servers`, VLAN 50, with the rest of them), a `dns/internal.yaml` entry, and
+this file plus `ssh-target` updated. **None of that was configured now** — an
+address that is about to be wrong is worse than DHCP.
+
+Expect ~65–80 ms RTT until it is wired. That is Wi-Fi power-save, not a fault.
+
+## Access
+
+`infra-ops` with NOPASSWD sudo (operator-bootstrapped). `lkraven` also has key
+auth but needs a password for sudo — **automation must connect as `infra-ops`**.
+
+## Headless conversion
+
+`playbooks/gx10-headless.yaml` — run it with the `infra-ops@` prefix, since
+elway's `--sudo` applies only to ad-hoc commands and playbook steps carry their
+own.
+
+Ships booting to `graphical.target` with GDM and GNOME Remote Desktop. The
+playbook sets `multi-user.target`, stops the remote-desktop service, masks the
+sleep/suspend/hibernate targets, tells logind to ignore lid and idle, and adds
+sshd keepalives so a stalled link does not kill a long job.
+
+⚠ **GDM is `static` on Ubuntu** — pulled in by `display-manager.service`, never
+"enabled". Guard and verify on `is-active`, not `is-enabled`; the latter passes
+trivially while the desktop is still running.
+
+The playbook will not stop GDM while someone holds a seat session. Override with
+`--var force_dm_stop=true`, or just let the rack-install reboot handle it.
+
+## Relevance to Flash-Next
+
+`sm_121`, not `sm_120`. The SGLang fork evaluated for ana-ml2 (henge item 49)
+narrows to **exact SM120 and explicitly excludes SM121/GB10** — it does not apply
+here. This chip has its own path: the DGX Spark recipe, which mmaps the ~48 GiB
+PLE n-gram table from NVMe rather than holding it in memory. 121 GB unified and
+822 GB of free NVMe make that viable on this box in a way it is not on a 96 GB
+discrete card.

servers/pfi-gx10/ssh-target

@@ -0,0 +1 @@
+infra-ops@10.100.10.226