===== Workflow =====
<code>
# First time setup:
docker-compose build    # Builds your custom image from Dockerfile
docker-compose up -d    # Starts containers using your custom image

# If you change the Dockerfile later:
docker-compose build    # Rebuild the image
docker-compose up -d    # Recreate containers with new image

# Or do both at once:
docker-compose up -d --build
</code>

===== File Operations =====
  * copy files to docker container: ''docker cp foo.txt container_id:/foo.txt''
  * copy files from docker container: ''docker cp container_id:/foot.txt foo.txt''
  * prune unneeded files (save disk space): ''sudo docker system prune -a -f''

===== Docker Maintenance =====
  * ''docker system df'': show overall space usage by category
  * ''docker inspect $(docker ps -q) | grep -A 10 Mounts'': see what volume goes with what container
  * ''docker inspect CONTAINER_NAME --format '{{range .Mounts}}{{.Name}} -> {{.Destination}}{{println}}{{end}}' '': list what volume is associated with the container
  * ''docker ps'': list docker containers
  * 

===== Housekeeping =====
  * When removing a service use ''docker compose down -v'' instead of ''docker compose down.''
    *  The ''-v'' removes the associated volumes at the same time.
  * When updating images, after pulling and restarting, run ''docker image prune'' to remove the dangling images
  * ''docker ps -a'': see all containers, even the ones that are stopped
  * 
==== Watchtower ====
  * Watchtower is a container which auto updates Docker containers
  * It will only update containers with updates that have the same tag
    * to always get the latest version use the tag ''latest''
    * you can check which images have which tags with ''docker images''
      * some images might have ''latest'' but not be base images so they won't be updated
  * check the logs: ''docker logs watchtower''
  * if you want Watchtower to skip trying to update an image add to ''docker-compose.yml''
<code>
 services:
  db:
    # label the image as each image gets its own label
    image: mariadb:latest # an example
    labels:
      - "com.centurylinklabs.watchtower.enable=false" # ADD THIS LINE
</code>
  * run watchtower immediately: ''docker run --rm -v /var/run/docker.sock:/var/run/docker.sock containrrr/watchtower --run-once''

===== Basic Operations =====
  * ''docker run'': run container
    * use the ''-d'' flag for "detach" i.e. run in background
    * use the ''-p'' flag to forward the port i.e. ''-p 9000:80'' maps port 80 in the container to 9000 on the host
    * user the ''--name'' flag to name the container (otherwise it's auto generated)
  * ''docker stop <ID>''
  * ''docker logs <ID>''
  * ''docker start <ID>'': restart a container
  * ''docker build <DIR_WHERE_Dockerfile_IS_LOCATED>'': build the image
    * ''-t'': add name and tag. Ex: ''docker build -t node-app:1.0 .''

===== Docker Registry =====
  * Docker Hub is the default registry and it is the biggest public registry
  * you can store a private or public registry on Docker Hub
  * Each application gets its on repo in the registry

===== creating a Dockerfile =====
  * All dockerfiles start with a parent image or "base image"
  * define the base image with ''FROM''
  * copy files into the container: ''COPY''
    * example: ''COPY package.json /app/''
  * set the working directory: ''WORKDIR''
    * example: ''WORKDIR /app''
  * next come the dependencies: ''RUN <dependencies here>''
    * example: ''RUN npm install''
  * for the last command in the docker file i.e. start the process: ''CMD''
    * example: ''CMD ["node", "server.js"]''