DevOps Classroom notes 05/Oct/2024

How Docker Works ?

• Container is an isolated space which will have its own Refer Here
  • process tree with the help of pid namespace
  • disk mounts with the help of mnt namespace
  • users with the help of usr namespace
  • network with the help of net namespace
  • CPU and RAM : with the help of cGroups
    
• Earlier Generation of Container creation incuded
  • docker engine directly interacting wiht linux kernel to create containers
    
• Docker has implemented runc to create containers
  
• OCI (Open container initiative was formed ) and the architecture of Docker has changed from monolith to layered

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Port forwarding

• Overview
  
• Let me create three applications in two containers each
  • nginx (it runs on port 80 )
  • jenkins (it runs on port 8080)
  • mysql container (it runs on port 3306)

docker container run -d --name nginx1 nginx
docker container run -d --name nginx2 nginx
docker container run -d --name jenkins1 jenkins/jenkins
docker container run -d --name jenkins2 jenkins/jenkins
docker container run -d --name mysql1 -e MYSQL_ROOT_PASSWORD=password mysql:8.0
docker container run -d --name mysql2 -e MYSQL_ROOT_PASSWORD=password mysql:8.0

* The above containers are not userful for me as i cannot access them from outside the vm.
* Delete all the containers docker container rm -f $(docker container ls -q -a)
* Delete all the image docker image rm $(docker image ls -q)
* For port forwarding we have two modes
* static -p <hostport>:<containerPort>


* Dynamic -P

* Lets apply dynamic Port forwarding

docker container run -d -P --name nginx1 nginx
docker container run -d -P --name nginx2 nginx
docker container run -d -P --name jenkins1 jenkins/jenkins
docker container run -d -P --name jenkins2 jenkins/jenkins
docker container run -d -P --name mysql1 -e MYSQL_ROOT_PASSWORD=password mysql:8.0
docker container run -d -P --name mysql2 -e MYSQL_ROOT_PASSWORD=password mysql:8.0

• Lets connect to jenkins
  
• Lets connect to nginx
  
• Lets connect to mysql