Explain basic management commands containers (pull, run, stop, delete, kill, inspect containers, remove images & see the logs etc ..)? #

Pulling an Image:

  • Downloads an image from a Docker registry
docker pull <IMAGE_NAME>

Pulling an Image with specific version:

  • Downloads a specific version of an image from a Docker registry
docker pull <IMAGE_NAME>:<SPECIFIC_VERSION>

# Example:
docker pull node:20.18

Pulling an Image from Private registry:

  • To pull a private Docker image from a registry, you need to follow these steps:
    • Docker Login: Authenticate with the registry using the docker login command:
      docker login <registry-url>
    • Pull the Image: Use the docker pull command with the full image name (including the registry URL)
      docker pull <registry-url>/<image-name>:<tag>
    • Example:
        docker login myregistry.example.com
  docker pull myregistry.example.com/my-private-image:latest

Running an Image:

  • Runs a container in detached mode and maps a host port to a container port
docker run -d -p <HOST_PORT>:<CONTAINER_PORT> <IMAGE_NAME>
  • Runs a container interactively with a terminal session
docker run -it <IMAGE_NAME> /bin/bash

Listing:

  • Lists currently running containers
docker ps
  • Lists all containers, including stopped ones
docker ps -a
  • Same as docker ps, lists currently running containers
docker container ls
  • Same as docker ps -a, lists all containers, including stopped ones
docker container ls -a

Start:

  • Starts a stopped container, typically one that has been stopped
docker container start <CONTAINER_ID or NAME>

Executing Commands Inside Container:

  • Starts a new interactive shell session in a running container
docker exec -it <CONTAINER_ID or NAME> /bin/bash

Copy from Host to Running Container:

  • Copies a file or directory from your host machine into a running container
docker cp /path/on/host <CONTAINER_ID_or_NAME>:/path/in/container

# Example:
docker cp ./app/config.json my_container:/usr/src/app/config.json

Stop:

  • Stops a running container by sending a SIGTERM signal, followed by a SIGKILL signal after a grace period, terminating all processes in the container
docker container stop <CONTAINER_ID or NAME>

Restart:

  • Restarts a running container
docker container restart <CONTAINER_ID or NAME>

Kill:

  • Immediately stops a container by sending a SIGKILL signal
docker container kill <CONTAINER_ID or NAME>

Pause:

  • Pauses all processes within the container, freezing them in their current state
docker container pause <CONTAINER_ID or NAME>

Unpause:

  • Unpauses all processes, allowing the container to continue from where it was paused
docker container unpause <CONTAINER_ID or NAME>

Remove:

  • Removes one or more stopped containers
docker container rm <CONTAINER_ID or NAME>
  • Removes all stopped containers
docker container prune

Inspection:

  • Returns detailed information about a container or image in JSON format
docker inspect <CONTAINER_ID or NAME>

View logs

  • Fetches the logs of a container
docker logs <CONTAINER_ID or NAME>
  • Fetches the logs of a container and follows the log output
docker logs -f <CONTAINER_ID or NAME>

Managing Images:

  • Lists all images on the local machine
docker images
  • Displays the history of an image, showing each layer that was created during the build process
docker history <IMAGE_ID>

Remove:

  • delete one or more Docker images from the local system
docker rmi <IMAGE_ID or NAME>

Build:

  • Builds an image from a Dockerfile in the current directory and tags it with the specified name
docker build -t <IMAGE_NAME> .

Cleanup:

  • Removes unused data such as containers, images, networks, and build cache
docker system prune

How do you set memory & CPU usage for containers & get Memory, and CPU usage info about specific containers? #

  • To limit the memory usage:
    • use the --memory (or -m) flag
  • To limit the CPU usage:
    • use the --cpus flag
docker run -d --memory="512m" --cpus="0.5" nginx:latest
  • Additionally, you can use --cpu-shares, --cpu-period, and --cpu-quota for more fine-grained control
  • Get Usage for a Specific Container:
docker stats CONTAINER_ID_or_NAME

Is there a way to see each layer & history of the image? #

  • Shows the history of an image, including the layers
docker history <IMAGE_ID>

Explain the Docker lifecycle #

Create:

  • Define a container from an image without starting it
 docker create --name mycontainer myimage

Start:

  • Run a container that has been created or restart a stopped container
 docker start mycontainer

Run:

  • Create and start a container in one step
 docker run --name mycontainer myimage

Stop:

  • Gracefully halt the processes in a running container
 docker stop mycontainer

Kill:

  • Forcibly stop a running container immediately
 docker kill mycontainer

Pause:

  • Suspend all processes in a running container
 docker pause mycontainer

Unpause:

  • Resume all processes in a paused container
 docker unpause mycontainer

Restart:

  • Stop and then start a container again
 docker restart mycontainer

Remove:

  • Delete a stopped container from the Docker host
 docker rm mycontainer

Example: Running Docker image