DevOps Classroom Series – 18/Aug/2021

Docker Continued

• Inside the container, applications get

  • cpu cycles
  • RAM
  • Disk space
  • process tree
  • network

• So applications have all of the things necessary to be executed, so they work in containers as they work in vm’s or physical system

• Container can be defined as an isolate area created on the system with

  • cpu
  • RAM
  • Disk /filesystem
  • process tree
  • network (ip address)
  • thin layer of os

• To create a container docker needs an Image.

• Initial Responsibilities of DevOps Engineer

  • Creating Docker Images for the applications developed
  • Sharing Docker Images with the servers where the application has to be deployed

Docker Simplified Architecture

• When we install Docker on any system, we get two major components
  • Docker client
  • Docker daemon (Docker Engine)
• When we want to run an application, we need to create a contianer, lets see the process in the following steps
• Steps when we try to create docker container:
  1. request made from docker client to create httpd container reaches the docker engine
  2. docker engine searches the httpd image locally
  3. Since the image is not present docker engine tries to download the image (pull) from docker registry. Default docker registry is dockerhub
  4. Once the image is pulled, docker engine creates the container from the local image pulled/downloaded
  5. The container will get a
     1. container id
     2. container name
     3. some cpu/memory
     4. an ip address
     5. filesytem from docker image