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
    Preview
  • Along with Repository (image name) and tag we also have image-id
    Preview

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
      Preview
    • examine disk mounts df -h
      Preview
  • 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.

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