Docker Docker Images and Containers Container Lifecycle Created Running Paused Stopped Deleted

1. Core Command / Concept

Create, manage, and delete containers. docker run.

2. Step-by-Step

1. Check if Docker is running: docker ps -a
   Output: List of all containers, including stopped ones.
2. Create a new container from an image: docker run -it --name mycontainer ubuntu
   Output: Container ID and a new shell prompt.
3. List all running containers: docker ps
   Output: List of running containers.
4. Pause a running container: docker pause mycontainer
   Output: Container is paused.
5. ⚠️ Stop a running container: docker stop mycontainer
   Output: Container is stopped.
6. Delete a stopped container: docker rm mycontainer
   Output: Container is deleted.
7. Clean up all stopped containers: docker container prune
   Output: List of deleted containers.

3. Real Commands with Examples

1. Purpose: Run a new container with a web server.
   Command: docker run -d --name webserver -p 8080:80 nginx
   Flags: -d runs container in detached mode, -p maps port 8080 on host to port 80 in container, --name sets container name.
2. Purpose: Run a new container with a shell and attach to it.
   Command: docker run -it --name myshell ubuntu
   Flags: -it allocates a pseudo-TTY and keeps the container running even after you detach.
3. Purpose: Run a new container from a specific image and set environment variables.
   Command: docker run -e MY_VAR=hello -it --name mycontainer ubuntu
   Flags: -e sets environment variable MY_VAR to hello.

4. Common Errors

1. Error: docker: Error response from daemon: Container cannot be paused: container is not running.
   Why: Container is not running.
   Fix: docker start mycontainer then docker pause mycontainer.
2. Error: docker: Error response from daemon: Container cannot be stopped: container is not running.
   Why: Container is not running.
   Fix: docker start mycontainer then docker stop mycontainer.
3. Error: docker: Error response from daemon: Container mycontainer is not running.
   Why: Container does not exist.
   Fix: docker container ls -a to check if container exists.

5. Quick Checks

1. Situation: Container is running but not responding.
   Command: docker logs -f mycontainer
   Correct response: Container logs are displayed.
2. Situation: Container is paused but not stopped.
   Command: docker ps -a
   Correct response: Container is listed as paused.
3. Situation: Container is deleted but still running.
   Command: docker container ls -a
   Correct response: Container is not listed.

6. Last-Minute Reference

• docker run command: docker run [options] image [command] [args...]
• Default port mapping: docker run -p 8080:80
• Environment variables: docker run -e MY_VAR=hello
• Container names: docker run --name mycontainer
• Container IDs: docker ps -q
• Container logs: docker logs -f mycontainer
• ⚠️ docker container prune deletes all stopped containers.
• ⚠️ docker system prune deletes all stopped containers, networks, and images.
• ⚠️ docker volume prune deletes all unused volumes.
• docker version command: docker version
• docker info command: docker info