frequent docker operations

docker_notes.md

## docker run
# [-d] run the container in detached mode, aka in the background
# [-p 80:80] map port 80 of the host to port 80 in the container
docker run -d -p 80:80 docker/getting-started

## docker build
# [-t] tag the image, a human-readable name for the final image
# [.] path to look for Dockerfile
docker build -t getting-started .

## remove a container
# get the ID of the container
docker ps
# stop the container
docker stop <the-container-id>
# remove the container
docker rm <the-container-id>
# stop and remove the container
docker rm -f <the-container-id>

## share via docker hub
# login into docker hub
docker login -u YOUR-USER-NAME
# tag the image with a proper name
docker tag getting-started YOUR-USER-NAME/getting-started
# push to docker hub with the default latest tag
docker push YOUR-USER-NAME/getting-started

## data persistance
# run ubuntu container
# start bash and run two commands
docker run -d ubuntu bash -c "shuf -i 1-10000 -n 1 -o /data.txt && tail -f /dev/null"
# get into the running container
docker exec <container-id> cat /data.txt
# run another ubuntu container
# run ls command
docker run -it ubuntu ls /
## create a named volume - just to store data
docker volume create todo-db
# start app with an attached named volume
# [-v] map host volume to container path
docker run -dp 3000:3000 -v todo-db:/etc/todos getting-started
# inspect details of a named volume
# [Mountpoint] the actual place where data is stored
# [driver] many 3rd party drivers available to support various storage options
docker volume inspect todo-db
## bind mount - we control the exact mountpoint on the host
# [-w /app] set the working dir that the command will run from
# [-v "$(pwd):/app"] bind mount current dir from host in the container into the /app dir
docker run -dp 3000:3000 -w /app -v "$(pwd):/app" node:12-alpine sh -c "yarn install && yarn run dev"
## inspect logs
docker logs -f <container-id>

## container networking
# If two containers are on the same network, they can talk to each other. If they aren't, they can't.
# 1) Assign it at start or 2) connect an existing container
# create a network
docker network create todo-app
# start a MySQL container and attach it the network
# [--network todo-app] create a network
# [--network-alias mysql] set network alias/hostname for connection from other containers
# [-v todo-mysql-data:/var/lib/mysql] create a volume automatically
# [-e MYSQL_ROOT_PASSWORD=secret] set env var for container
docker run -d --network todo-app --network-alias mysql -v todo-mysql-data:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=secret -e MYSQL_DATABASE=todos mysql:5.7
# connect to container
docker exec -it <mysql-container-id> mysql -p
# start new container - nicolaka/netshoot, for network debugging
docker run -it --network todo-app nicolaka/netshoot
# look up the IP address for hostname mysql
dig mysql
# connect to mysql container for dev work
docker run -dp 3000:3000 -w /app -v "$(pwd):/app" --network todo-app -e MYSQL_HOST=mysql -e MYSQL_USER=root -e MYSQL_PASSWORD=secret -e MYSQL_DB=todos node:12-alpine sh -c "yarn install && yarn run dev"
# verify status of the container
docker logs <container-id>
# confirm data is written into the database
docker exec -ti <mysql-container-id> mysql -p todos

## docker compose
# start multi container app
docker-compose up -d
# shut down
docker-compose down
# inspect logs
docker-compose logs -f <service_name>

## image layers
# inspect layers that made up an image
# base layer shows at bottom
docker image history --no-trunc getting-started
# layer caching
# once a layer changes, all downstream layers have to be recreated as well
# place common image close to base image
# .dockerignore file can be used to skip copy of folders/files

## multi-stage build - in Dockerfile
# FROM maven AS build
# ...
# FROM tomcat
# COPY --from=build /app/target/file.war /usr/local/tomcat/webapps