`docker image ls` on Docker 29 leaves out images with no tag, which is every
image a swarm task pulled by digest: the check run on VDNT-Docker03 saw 4 of
its 58. Missing them only kept them, but superseded digests there would
never have gone. The list now comes from GET /images/json on the socket.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The nightly prune ran `docker system prune -a`, which deletes every image no
local container uses, so each swarm node kept only its own tasks' images.
When the other node failed or was drained, its services had to pull first:
on 2026-10-25 Traefik took 11.5 min to start on Docker03.
maintenance/swarm_prune.yml (built in) prunes stopped containers, unused
networks, dangling images and build cache, then removes only the images that
no container uses and no swarm service is pinned to, wherever that service
runs. Old digests left by redeploys still go.
- A container's image is kept by its id and by the reference it was made
from, since on the containerd store the id alone hasn't held a tag.
- A node that can't list the swarm's services removes no images and fails
rather than pruning blind.
- Check mode lists what would go.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>