Docker

Interact with Docker containers and images using the Docker CLI. This skill provides best practices for managing containers, inspecting logs, cleaning up unused resources, and using Docker Compose.

For detailed usage and commands, refer to the official Docker documentation.

Usage

Run docker commands directly.

docker [subcommand] [flags]

Common Operations

List Containers

Use formatting to get a clean table view of running containers.

docker ps --format "table {{.ID}}\t{{.Image}}\t{{.Status}}\t{{.Names}}"

To list all containers (including stopped ones):

docker ps -a --format "table {{.ID}}\t{{.Image}}\t{{.Status}}\t{{.Names}}"

View Logs

Follow logs for a specific container, limiting the output to the last 100 lines to avoid flooding the console.

docker logs --tail 100 -f <container_name_or_id>

Inspect a Container

Get detailed information about a container in JSON format.

docker inspect <container_name_or_id>

Clean Up Resources

Remove unused data (stopped containers, unused networks, and dangling images). Be careful with this command.

docker system prune -f

To remove all unused images, not just dangling ones:

docker system prune -a -f

Execute Command in Container

Run an interactive shell inside a running container.

docker exec -it <container_name_or_id> /bin/bash
# or if bash is not available:
docker exec -it <container_name_or_id> /bin/sh

Docker Compose

Manage multi-container applications defined in docker-compose.yml or compose.yml.

Start Services

Start services in the background.

docker compose up -d

View Compose Logs

View logs for all services in the compose stack.

docker compose logs --tail 100 -f

Stop Services

Stop and remove containers, networks, and volumes defined in the compose file.

docker compose down

Troubleshooting

• Permission Denied: If you encounter permission errors, ensure the user is in the docker group or try using sudo (though sudo usage depends on environment configuration).
• Daemon Not Running: If docker commands fail with "Cannot connect to the Docker daemon", ensure the Docker service is running (sudo service docker start or equivalent).