DevOps Classroomnotes 04/Nov/2022

Installing Docker in Azure Linux VM

• Refer Here
• Create a Linux vm (Standard_B1s). Login into instance

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

• Install the docker and add current user to docker group

docker info

Image and Tag

• Any docker image represents some application. Every application will have multiple versions.
• In Docker to represent application we use name of image and to represent version we use tag. The convention <image-name>:<tag>

hello-world => hello-world:latest

• If the tag is not passed docker assumes the tag to be latest
  
• Along with Repository (image name) and tag we also have image-id
  

Container Options

• We can perform the following operations
  • Create container
  • Delete container
  • start container
  • stop container
  • pause container
  • unpause container
• Every container when created gets a unique
  • container id
  • container name
• We can set the container name

docker container run --help
docker container run --name <cont-name> <image>:<tag>

• To see the container running in the docker host docker container ls, to see the status of all the containers created by docker host which are not deleted docker container ls --all
• When the container is created, each container gets its own
  • network ip address
  • RAM
  • filesystem
  • CPU share
• Execute docker stats to know the cpu/RAM utilization

Exploring container

• On the docker host execute the folowing commands
  • list all the process ps or ps aux
  • get the ip address ip addr or ifconfig (10.2.0.4)
  • username => qtdevops
  • hostname => qtdocker
  • Explore storage df -h & lsblk
• Lets create a container and login into that docker container run -it alpine /bin/sh
• Execute the following commands
  • find username and hostname whoami and hostname (root & 03558710c5d9)
  • ip address ip addr (172.17.0.4)
  • examine the running process ps
    
  • examine disk mounts df -h
    
• Based on all of the observations a container looks like a linux machine inside a linux machine i.e virtual machine
• Docker image contains all the necessary files to run whatever application we want inside container.

Next Steps

• Lets install a java application on a linux machine
• Lets try to also run the same java application inside some container and understand the docker image concept
• Lets create a docker image and also understand its read-only nature.