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What is a Container

  • Docker containers are often compared to virtual machines but they are actually just processes running on your host OS.
    • A container is an isolated (namespaces) and restricted (cgroups, capabilities, seccomp) process.
  • On Linux you can run ==ps aux== and see the process
  • Detailed explanation on containers

Run Containers​

Run Containers in the Foreground​

docker container run -it -p 80:80 Nginx
# -it = interactive
# -p = port mapping public_port:container_exposed_port

What Happens in the Above Command?​

  • Look for an image called Nginx in the image cache
  • If not found in the cache, it looks to the default image repo on Dockerhub
  • Pulls it down (latest version), store it in the image cache
  • Started it in a new container
  • We specified to take port 80 on the host and forward to port 80 on the container
    • We would do ==$ docker container run -d -p 8000:80 nginx== to use port 8000
  • We can specify versions like "nginx:1.09"

Run Container in the Background​

docker container run -d -p 80:80 nginx  
#-d = run in detached mode => no showing log**

Naming Containers​

docker container run -d -p 27017:27017 --name my_awsome_mongo mongo

docker container run -d -p --name my_awsome_mongo 27017:27017 mongo

Run Containers with Environment​

docker container run -d -p 3306:3306 --name mysql --env MYSQL_ROOT_PASSWORD=123456 mysql

#then we would be able to access process.env.MYSQL_ROOT_PASSWORD inside the code
docker run --name postgresql -e POSTGRES_USER=myusername -e POSTGRES_PASSWORD=mypassword -p 5432:5432 -v /data:/var/lib/postgresql/data -d postgres

List Containers​

List Only Running Container​

docker ps

List All Containers Either Running or Not Running​

docker ps -a
# -a = all

Stop Container​

docker stop [container_id]

Stop All Running Containers​

docker stop $(docker ps -aq)

Remove Container​

First stop the container as you can not remove a running container

docker rm [container_id]

Remove Multiple Containers​

docker rm [container_id1] [container_id2]

Force Remove a Running Container​

docker rm -f [container_id]

Remove All Containers​

docker rm $(docker ps -aq)

Journey Inside Containers​

#docker container exec -it [container_name] bash
docker container exec -it MySQL bash

Logs​

  • Print the last 100 lines of a container’s logs
docker container logs --tail 100 [container_name]