# Valhalla on the Jetson: arm64 viability and the driving-side trap

**Date:** 2026-09-04  
**Host:** `mikkeli-orin-nano-2` (192.168.2.209), aarch64, Ubuntu 22.04.5, L4T R36.4.7 / JetPack 6  
**Outcome:** arm64 works. A separate, silent correctness bug was found and fixed.

## Why this was investigated

Valhalla's arm64 container support was recorded as the one real integration risk
in the navigation workstream, on the strength of a long-running upstream issue
(valhalla/valhalla#3424) about building arm64 images. Everything else in the
workstream was blocked behind the answer.

## arm64: not a risk

The issue is stale. Checked before pulling anything:

```
docker manifest inspect ghcr.io/valhalla/valhalla:latest
  → linux/amd64, linux/arm64
```

Both `ghcr.io/gis-ops/docker-valhalla` and `ghcr.io/nilsnolde/docker-valhalla`
also publish arm64. The official image runs natively; `valhalla_build_config`,
`valhalla_build_admins` and `valhalla_build_tiles` all execute. Version 3.8.3.

Full pipeline verified: config → timezones → admins → tiles → served route.

| Measurement | Value |
|---|---|
| Shikoku PBF | 49 MB |
| Routing tiles from it | 149 MB |
| Whole-Japan PBF | 2.4 GB |
| Admin DB from whole Japan | 17 MB |
| Timezone DB | 116 MB |
| Route Takamatsu → Matsuyama | 157 km, 112 min |

Japanese street names survive intact in the route narrative
(`高松南バイパス`, `高松停車場栗林公園線/173`), so CJK is fine on the routing
path as well as the rendering path.

A benign warning appears at startup:

```
[ERROR] (stat): /data/valhalla/tiles.tar No such file or directory
[WARN] Tile extract could not be loaded
```

The server falls back to the tile *directory*, which is the form we want anyway.
Not an error condition. Do not "fix" it by switching to the tar.

## The actual finding: a sub-region extract silently mirrors the map

The plan said to start from a regional extract to keep artifacts small. That is
correct for routing tiles and **wrong for the admin database.**

Built from `shikoku-latest.osm.pbf`:

```
by admin_level: [(4, 4)]
  (4, '36', '徳島県', drive_on_right=1)
  (4, '39', '高知県', drive_on_right=1)
  (4, '38', '愛媛県', drive_on_right=1)
  (4, '37', '香川県', drive_on_right=1)
```

No `admin_level=2` row at all, and right-hand traffic on every prefecture.

Built from `japan-latest.osm.pbf`:

```
by admin_level: [(2, 1), (4, 47)]
  (2, 'JP', '日本', 'Japan', drive_on_right=0)
```

Driving side is a **country-level** property. A Shikoku-clipped extract does not
contain Japan's country boundary, so no country record exists and the value
defaults to 1.

### Why this is dangerous

`valhalla_build_admins` **exits successfully.** Nothing warns. Nothing fails. The
tiles build fine and the server serves routes. The first symptom is a turn
instruction that is subtly wrong, on a road the driver may not know well.

### The fix

The admin build and the tile build are separate invocations reading the same
config, so they can take different inputs:

- admins ← `japan-latest.osm.pbf` (always the full country)
- tiles ← whatever regional extract is wanted

Cost is one 2.4 GB download, which is not repeated per region.

### The rule that follows

Never assume this worked. Every build asserts that a country-level row exists and
reports `drive_on_right=0` before its tiles are treated as usable. A check is
cheap; the failure is silent and the consequence is on a road.

## Left on the host

`~/valhalla-test/` — 2.8 GB, kept deliberately. It is a working Valhalla install
with the Japan PBF already fetched, which is the expensive part to reproduce.