---
type: reference
title: Dankclaw Swap Configuration
description: "The host swapfile: why it is sized as it is, the resize ordering that avoids an OOM, and the swappiness caveat."
tags:
  - dankclaw
  - host
  - memory
  - swap
timestamp: 2026-09-12
---

# Dankclaw Swap Configuration

**Host:** Dankclaw (192.168.0.143) — **Filesystem:** ext4 on `/dev/nvme0n1p2`

| Item | Value |
| --- | --- |
| Swapfile | `/swap.img` (68,719,476,736 B = 64 GiB, owner root 0600, mtime 2026-09-12 21:56 — `ls -la /swap.img`) |
| Size | **64 GiB** (raised from 8 GiB on 2026-09-12); `/proc/swaps` reports 67,108,860 KiB |
| Type / priority | `file`, priority **-1** — the only swap device on the host (`swapon --noheadings` 2026-10-18: `/swap.img file 64G 187.6M -1`) |
| Filesystem | ext4 on `/dev/nvme0n1p2` (`df -T /` 2026-10-18) — swapfiles fully supported, no btrfs `nocow` handling needed |
| Allocation | `fallocate` (preallocated, hole-free; **530 extents** — `sudo filefrag -v /swap.img` → "530 extents found", 2026-10-18) |
| Persistence | `/etc/fstab` line 12: `/swap.img none swap sw 0 0` (`grep -n -i swap /etc/fstab` 2026-10-18) |
| systemd unit | `swap.img.swap` — `LoadState=loaded`, `FragmentPath=/run/systemd/generator/swap.img.swap`, `UnitFileState=generated`, `is-active` → `active` (2026-10-18) |
| `vm.swappiness` | `60` (distro default, unchanged — `sysctl vm.swappiness` 2026-10-18) |
| zswap | disabled (`/sys/module/zswap/parameters/enabled` = `N`, 2026-10-18) |
| Swap in use | 187 MiB of 63 GiB (`free -h` 2026-10-18) |
| Free on `/` | **424 GiB of 1.9 TiB, 77 % used** (`df -T /` 2026-10-18). The 748 GiB that stood right after the 2026-09-12 resize is gone — ordinary fleet writes since then |

The unit is **generated from fstab**, not a hand-written unit file. fstab is the
only control point; `systemctl daemon-reload` re-reads it. Nothing in this
repository references the swapfile — it is host-level state, documented here so
it is not invisible.

## Why 64 GiB

Dankclaw is shared. The 2026-09-12 decision measured `frank-dragoon` alone holding
**103.5 GiB of the 121.2 GiB** host, leaving roughly **7.1 GiB** for the then-28
co-tenant containers whose working set was ~4.3 GiB. How that total is split
between weights, KV pool and working memory is the engine's own ledger — it lives
on [[frank-dragoon]]. That is a decision-time reading, not today's: on
2026-10-18 the host reports **91 GiB used / 29 GiB available of 121 GiB**
(`free -h`), 30 containers are up (`podman ps -q | wc -l`), and the
`frank-dragoon-halogen` container accounts for **70.33 GiB**
(`podman stats --no-stream`, same day).
The engine itself warned at the time that when the headroom runs out,
frank-dragoon and its neighbours "can stall for minutes at a time at full CPU with
no disk activity and no output". Swap is the valve that turns an OOM kill into slow
paging.

Swap does **not** relieve the pinned-weights problem — see the caveat below.
It protects the *co-tenants* and buys headroom for burst allocation.

## The safe resize ordering

You cannot grow an active swapfile; it must be swapped off first. On a host
like this, **never `swapoff` before the replacement is online.** The old 8 GiB
held 4 GiB of live pages, and `MemAvailable` read 73 GiB while only ~5 GiB was
genuinely free — the pinned model weights are counted as reclaimable page
cache, so the headline number is a lie by roughly the size of the model
(see [[frank-dragoon]]). Swapping off into that apparent space, with
nothing else to receive the pages, is how you invite the OOM killer.

The ordering that avoids it — create and enable the new swap **first**, so the
pages have somewhere to go:

```bash
# 1. Preallocate + format + enable the replacement, old swap still live
sudo fallocate -l 64G /swap2.img
sudo chmod 600 /swap2.img
sudo mkswap /swap2.img          # also rejects files with holes
sudo swapon /swap2.img          # total swap now 72 GiB

# 2. Only now drain the old one — pages migrate into /swap2.img, not into RAM
sudo swapoff /swap.img          # took 65 s for 4 GiB

# 3. Consolidate onto the conventional path so fstab needs no edit
sudo swapoff /swap2.img         # 725 MiB left, trivial
sudo mkdir -p ~/.AGENTTRASH/20260912-swapfile-8g
sudo mv /swap.img ~/.AGENTTRASH/20260912-swapfile-8g/swap.img
sudo mv /swap2.img /swap.img
sudo swapon /swap.img
```

Step 3 is chained tightly because it leaves the host with **zero swap** for a
few seconds. Do not leave that window open.

`mkswap` succeeding is itself a check: it refuses swapfiles containing holes,
so a `fallocate` that produced a sparse file fails here rather than at 3 a.m.
under memory pressure.

## Verification

```bash
swapon --show=NAME,TYPE,SIZE,USED,PRIO   # /swap.img file 64G 187.6M -1 (2026-10-18)
systemctl is-active swap.img.swap        # active; FragmentPath=/run/systemd/generator/swap.img.swap
grep -n swap /etc/fstab                  # line 12 intact -> boot persistence
free -h | tail -2                        # Swap: 63Gi total, 187Mi used (2026-10-18)
```

Then confirm the inference service is unaffected — a completion, not just
`/health`:

```bash
curl -s http://127.0.0.1:7770/v1/chat/completions \
  -H 'Content-Type: application/json' \
  -d '{"model":"frank-dragoon","messages":[{"role":"user","content":"Reply with exactly: SWAP64-OK"}],"max_tokens":48,"reasoning_effort":"low"}'
```

As run 2026-09-12: `finish_reason: stop`, `SWAP64-OK`, 28 containers up,
frank-dragoon `health=200` throughout.

## Caveats

- **Swap cannot help the pinned weights.** frank-dragoon's weights are pinned
  deliberately; paging them is a stall, not a relief. More swap does not make a
  larger KV pool affordable — see the reserve/pool ceiling in
  [[frank-dragoon]].
- **`vm.swappiness=60` is untested against this workload.** Under real
  pressure the kernel will happily page anonymous memory, and frank-dragoon's KV
  pool and working set *are* anonymous. Swapping the KV pool would be far worse
  than the OOM kill it prevents. If the box ever starts thrashing, lowering
  swappiness (or capping the engine's cgroup) is the knob, not more swap.
- **`free` still lies after the change.** On 2026-09-12 `MemAvailable` read ~70 GiB
  while the model was loaded; on 2026-10-18 it reads **29 GiB** with 90 GiB sitting in
  `buff/cache` (`free -h`). The headline number moves with the payload; trust the
  engine's `host memory left for everything else` line, not `free`.

- **Filesystem prerequisite (other hosts).** ext4 and xfs take swapfiles
  directly. btrfs needs `chattr +C` (NOCOW), no compression, and no
  snapshots in the swapfile path — check `df -T` before planning, or
  `mkswap` will reject the file.
- **Renaming an *active* swapfile works (inode-based) but leaves a stale
  path in `/proc/swaps`** — swap it off first, then rename, then `swapon`
  (which is exactly what the step-3 consolidation does). Migration is
  observable while it runs: in the 2026-09-12 run `swapoff` of 4 GiB took
  65 s and used-RAM rose only ~3 GiB (pages touched during migration), the
  rest relocating on disk. If used-RAM climbs toward the whole swapped
  amount, let it finish rather than aborting.

## Trash

The previous 8 GiB `/swap.img` (dated 2026-07-21) was staged, not deleted, at
`dankclaw:~/.AGENTTRASH/20260912-swapfile-8g/swap.img` (8.1 GiB). **That staging
directory no longer exists** — `ls /home/dank/.AGENTTRASH` on 2026-10-18 lists only
`20261005-frank-small-ubatch-ab`, `20261006-frank-large-tuning`
`20261007-openwebui-modelpicker`, `20261010-fleet-rename`, `20261017-bonsai-scratch`
`20261017-prism-build`, `20261017-v2abl-trial`, and there is no `/root/.AGENTTRASH`.
The old swapfile has therefore been purged; nothing on the host still holds it.

## See Also

- [[frank-dragoon]] — the memory model that motivated this
- [[Dankclaw System Specs]] — the Strix Halo box
- [[Dankclaw Improvements]] — other host-level changes