DevOps Classroom notes 03/Jan/2024

Docker installation Details

• Docker when installed on a linux machine creates a group called as docker group.
• docker client communicates with docker server (docker daemon) on the unix socket which is accessible only to the users of docker group.
• So after installation add your user to docker group

sudo usermod -aG docker <user-name>
# exit
# relogin

* Now get the docker information docker info to see both client and server details

Running our first container

• To run the docker container we need docker image (which has all the necessary stuff packaged to run the application)
• Steps
  1. docker contianer run is issued from client
  2. docker daemon checks in the local image store
  3. if not present downloads from registry (docker hub)
  4. runs the container
     
• To view the images in docker local store docker image ls

Getting used to docker commands

• Two ways
  • help. use --help
  • cheatsheet
    

Figure out docker commands

• create a docker network docker network create
• list docker volumes docker volume ls
• stop the docker container
• remove the docker image
• build the docker image
• start all the containers using docker compose
• stop all the containers docker compose

What is present in docker image and how containers are created

• To understand this we need to understand
  • cgroups: These put restrictions (256 MB of RAM 1 vcpu)
  • namespaces: This creates virtual isolated
    • process trees
    • mounts
    • users
    • network interfaces