docker/server.Dockerfile installed Debian's `docker.io` to get a client for the
socket mounted by Compose. That package is the full ENGINE: even with
--no-install-recommends it pulls 15 packages including containerd, runc, dmsetup
and iptables, none of which a container that only talks to a mounted socket can
use, and it ships Docker 20.10.24 (2023).
Copy the CLI and the buildx plugin from the official docker:29-cli image
instead. Measured on the same node:22-bookworm-slim base: 266 MB -> 108 MB, so
158 MB smaller with a current CLI (29.7.2) in place of a two-year-old one.
Three things verified rather than assumed, by building the real image and
running it:
- docker:cli is an ALPINE image, so copying a binary into this Debian one is
only safe because the binaries are static Go builds (ldd: "Not a valid dynamic
program"). In the built image, `docker --version`, `docker ps` and
`docker build` all work against a mounted host socket as the unprivileged
runtime user.
- buildx is copied on purpose. scripts/build-agent-image.mjs shells out to
`docker build` and Codeman auto-builds the agent image on the first Docker
case. Without the plugin that still works today — CLI 29 falls back to the
classic builder, tested — but that builder is deprecated and will be dropped,
so the plugin keeps the path supported.
- docker-compose is NOT copied: Codeman never shells out to it.
Pinned to the 29 major, matching how the base images here are pinned.
Codeman maintainer