How to run Docker inside Docker Container?

Step 1 : Docker pull centos

Step 2 : 1. mkdir storage

          2. cd storage/

Step 3 : docker run -it --privileged -v /root/storage:/var/lib/docker --name os1 centos

1.   We used privileged mode because to run docker engine inside docker container it will be failed due to some security reason. A privileged container means it have all root capabilities of host machine

2.   Docker store all data like containers, images, networks, plugins and many mores inside in one place that is /var/lib/docker, so this folder is most important folder. We know if we terminate any container than all the content inside the container will be removed. So, for that reason we create a folder that is mystorage inside in host machine and linked this folder with that folder /var/lib/docker means we create a persistent storage of that folder /var/lib/docker

Now we install docker on centos environment for that first we create a repo file inside in /etc/yum.repos.d

Step 3 : vi /etc/yum.repos.d/docker.repo

Step 4 : Write this command

Write this content to this repo file

[docker]

baseurl=https://download.docker.com/linux/centos/7/x86_64/stable/

gpgcheck=0

Step 5 : yum install -y docker-ce --nobest

Step 6 : dockerd &

This will start the docker in background and now u can execute the docker commands

Step 7 : 1. docker pull alpine

          2. docker images

          3. docker run -it --name os2 alpine
         
          4. docker ps