* Actually, it was mariadb that didn't have an arm v7 component. When I switched to a different mariadb image (`jsurf/rpi-mariadb:latest`), docker-compose worked. What's weird is that it seems like there already is an arm v7 image for farmOS:
```
Pulling www (farmos/farmos:dev)...
dev: Pulling from farmos/farmos
```