Docker Commands

Docker Commands

• Run or start a container docker run nginx will pull locally installed or remote container and run it.
• ps - list containers docker ps
• list the all containers - docker ps -a It will list exited all previously containers running
• Stop Container docker stop silly_sammet will stop running container named silly_samet (use name or ids)
• Rm - Remove a container docker rm silly_sammer will delete stopped container named silly_sammer
• Images - List Images docker images Lists local available images on the host
• Rmi - Remove images docker rmi ngnix will delete the local images
• pull - download remote images docker pull nginx it will only pull images and not run em
• append a command docker run ubuntu docker run ubuntu sleep 5 It will run second command as a process in empty container
• exec - execute a command docker exec <name/ID> cat /etc/hosts exectute a command in running container
• run - attach mode docker run kodekloud/simple-webapp command like webserver will run in foreground aka attach mode to exit from them press ctrl + c or ctrl + z to suspend em in bg
• run - dettach mode docker run -d kodekloud/simple-webapp this will run the command in dettach mode aka background mode
• it - interactive mode docker run -it centos bash This will log you into console of containerized os
• tags - run specific version `docker run ubuntu:12.04 this will run or pull image name ubuntu of version of 12.04 tag
• port mapping docker run –p 80:5000 kodekloud/simple-webapp This will map port 80 of the host machine to forward traffic onto port 5000 inside container.
• volume mapping docker run –v /opt/datadir:/var/lib/mysql mysql This will map default /opt/datadir directory on the host machine to /var/lib/mysql inside docker container. By using this volume mount, you ensure that the data stored in the MySQL container is persisted on the host machine, even if the container is stopped or removed.
• inspect container docker inspect <name/id> _This will give all configuration details of the specific container _
• seeing logs docker logs <name/id> Useful for debuging issues
• setting up enviromental variables docker run -e APP_COLOR=green simple-webapp-color Useful for changing programmable variable inside a program or container

Container Orchestration

when one container is becoming out of load and capacity to hold more users and data processing new instances of the container need to be spawn. Container Orchestration contains tools that make this process easy and automated. example: docker service create --replicas=100 nodejs

There are various docker orchestration solutions available some common are:

1. Docker Swarm from docker
2. Kubernetes from Google
3. MESOS from Apache

Kubernetes

In docker you might run one instance of container like this: docker run my-web-server

but in kubernets you run multiple instance of them like this: kubectl run --replicas=1000 my-web-server

you can scale them if 1000 arent enough kubectl scale --replicas=2000 my-web-server

you can even roll update into them kubectl rolling-update my-web-server --image-web-server:2

or rollback updates if it made them unstable kubectl rolling-update my-web-server --rollback

1. Node - Is a machine physical or virtual on which kubernetes and its set of tools installed. In nodes there are worker machines where containers will be launched by kubernetes. 2. Cluster - Is a set of nodes grouped together so even if one node fails your application will be still accessible by other active nodes. 3. Master - Is a node where kubernetes control plane component installed. Master manages the nodes and it responsible for actual orchestration of containers on the worker nodes.

Some commands of kubernetes

Run a cluster kubectl run hello-mincube

Get Cluster info kubectl cluster-info

get nodes kubectl get nodes

run 100 instances of my-web-app container images kubectl run my-web-app --image=my-web-app --replicas=100