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