If you regularly build or pull images on a Docker host, disk usage can creep up quickly.
Most people know that Docker (and Podman) keeps old images around unless you prune them. What’s less obvious is the build cache. When you build images, like the Domino container, Docker stores intermediate layers, so future builds can be faster.
Even if you build with --no-cache (as the Domino build script does), Docker still writes layers to the build cache. They’re just not reused. Over time, that cache can grow significantly.
In my case, it explained why my root disk was filling up: 25+ GB of build cache.
This is a companion discussion topic for the original entry at https://blog.martdj.nl/2026/05/22/building-your-own-domino-containers-dont-forget-to-prune-docker/