| name | docker |
| description | How to run, manage, and troubleshoot Docker containers, images, and networks safely via the command line. |
| license | MIT |
Skill: docker
Execute, inspect, and manage Docker containers, images, and network components directly via the CLI, adhering to safe operational boundaries.
Core Principles
- Non-Interactive Execution: Never use
-it or interactive pseudo-TTY modes when executing container commands autonomously. Always run in detached (-d) or batch execution modes.
- Resource Cleanup: Always use
--rm for ephemeral run commands to prevent container accumulation. Clean up unused images regularly using docker system prune, and prune unused volumes with docker volume prune or docker system prune --volumes.
- Absolute Paths for Mounts: When binding volumes via
-v, strictly use absolute paths ($PWD or full paths) rather than relative paths.
- JSON Formatting: When querying for container state or image details, prefer structured output (
--format '{{json .}}') for robust parsing.
Commands / Usage Patterns
- Run Ephemeral Containers:
docker run --rm -v "$PWD":/work -w /work <image> <command>
- Run Detached Services with Port Binding:
docker run -d --name <container_name> -p <host_port>:<container_port> <image>
- Execute Commands in Running Container (Non-Interactive):
docker exec <container_name> <command>
(Avoid -it for automated agent workflows)
- Stream Logs with Timestamps:
docker logs --timestamps --tail 50 <container_name>
- Inspect Container Details via JSON:
docker inspect --format='{{json .State.Health}}' <container_name>
- List Running Containers (Structured Output):
docker ps --format '{"ID":"{{.ID}}", "Image": "{{.Image}}", "Names":"{{.Names}}", "Status":"{{.Status}}"}'
- Build Image with Tags:
docker build -t <image_name>:<tag> -f <Dockerfile_path> .
Diagnostics and Troubleshooting
- Debugging Failed Starts: If a container exits immediately, run
docker logs <container_name> to trace startup errors.
- Inspecting Mount Permissions: For
permission denied errors inside the container, verify host directory permissions or apply SELinux volume labels (:z or :Z).
- Network Resolution Issues: If containers cannot reach each other, verify they share a user-defined network using
docker network inspect <network_name>.
What to Avoid
- Do not run interactive sessions (
docker run -it or docker exec -it). These will hang automated agents.
- Do not parse tabular
docker ps or docker images output using grep or awk when --format json templating is available.
- Do not leak credentials via CLI arguments or environment variables (
-e PASSWORD=xyz). Use docker secret (Swarm) or mount credential files securely.
Limitations
- The agent cannot solve authentication steps interactively (e.g.,
docker login without a password feed).
- Building massive images may exceed time-to-live execution limits; prefer optimized caching.
Related Skills
- shell:
You MUST load this skill when handling shell commands with performance monitoring or timeouts.
- dockerfile:
You MUST load this skill when writing, reviewing, or optimizing Dockerfiles.
