Modern Docker image (docker/modern/) — reference

An alternative server image based on Alpine/musl. Contributor-facing musl gotchas live at .claude/rules/modern-docker.md.

Status: WIP / experimental. Not finished, not fully tested, and not in production use — the production image remains docker/Dockerfile (Debian/glibc). It is not built by the Makefile or CI; it builds manually via docker/modern/docker-compose.yml.

Stack

• Base: Alpine:edge
• Display: Xvfb + Openbox
• Audio: PipeWire
• Streaming: WebRTC (go2rtc)
• Init: s6-overlay

Image size

• ~821 MB total (vs ~960 MB for the existing Debian image).
• 465 MB of that is Mesa/LLVM for software OpenGL.

Architecture choices

• Game files are not baked in — runtime download via the steam-auth shared volume.
• Wayland/Cage abandoned: no OpenGL in headless Docker without a GPU. Use Xvfb + Openbox instead.
• Openbox required: without a window manager, window resize during startup crashes (null Farmer).