DevOps Classroom Series – 21/Aug/2021

Containers Continued

• Lets create a new nginx container
• Inspecting containers
  • Command: docker container inspect <container-name/id>
  • Containers have lot of associated data that characterizes its behavior, To get the information we can use inspect command
  • The response from inspect is a json object with full of details
• We have started the container in detached mode, now lets try to attach to the container

docker container attach <container-name/id

• Once we attach to the container and use Ctrl+c then the container will be stopped.
• To quit from the attached mode without stopping container (Ctrl+ pq)
• When the application in a container writes the logs to stdout and stderr, we can view those logs from logs command

docker container logs <container-name>

• If you want to get only last few entries

docker container logs --tail 5 <container-name>

• If you want to follow the logs

docker container logs --tail 5 --follow <container-name>

• When we create containers, container run on the internal network which is not accesible from outside world, but we would still want to access the applications running inside containers.
• So while creating containers we can do port forwarding. This port-forwarding forwards the request recieved on the host (machine where docker is installed) on some specific port to the port in the container
• If we want to specify the manual ports to be mapped then

docker container run -p <port on host>:<container port> <image>
docker container run -d -p 32660:80 --name webserver nginx

• There is also an option to dynamically create port forwarding

docker container run -P <image>

• Executing commands in the docker container

docker container exec <container-name> <command>

• Now if you want to login in into docker container terminal for already created container

docker container exec -it <container> <terminal>

• Note: When we try to work in containers in many cases you might not find all the linux utilities inside the container & this is for greater good. The container should not have any additional tools/utilities apart from what are required to run your application.
• If you want to run the contianer (create a new container) in the interactive mode

docker container run -it <image-name> <terminal>

Installing docker

• Lets try to install docker on a Linux Machine
  • Create a ubuntu VM in AWS:
  • Create a ubuntu VM in Azure
• note:
  • AWS EC2 instance: Refer Here
  • Azure VM: Refer Here
• To install docker on a linux machine

curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh

• Now to give the access of docker to non root users, we need to add them to docker group

whoami
sudo usermod -aG docker $(whoami)
# Now logout and login into the terminal 
docker version

• Docker can also be installed on Desktops

  • Windows 10 Refer Here
  • Mac Refer Here

• Note: Docker Commands

  • Docker commands in the earlier versions were docker <command> but docker now recommends using docker <context> <command>