docker and kubernetes notes

docker-and-kubernetes-notes.md

Docker

• To create docker image from Dockerfile, run docker build . -t <your-image-name>
• to run the created docker image, run docker run -d --publish <localhost-port>:<container-port> <your-image-name>
• To view the created image in the images list, run docker image list. this should list the created image
• Once completed, to verify the contents of the image, run docker run -ti <your-image-name> bash
• To verify the contents of the container, run docker exec -it <your-container-name> bash
• To delete a docker image, run docker image rm <space-seperated-image-names> -f
• To create images from a yml file, run docker compose build. This will by default pick docker-compose.yml and Dockerfile files. To build image through a different config file then run docker compose -f <custom-config-yml> build.
• To run containers through docker-compose.yaml file, run docker compose up. For a different yaml file, run docker compose -f <your-config-yaml-file> up

Kubernetes

• To give an alias name for your kubectl: alias k="microk8s kubectl" and use it as k get pods/svc (in windows powershell, run Set-Alias k then enter microk8s kubectl as value)

• To create objects (service/deployment) from (multiple)config file: kubectl create -f config1.yaml -f config2.yaml

• To delete objects defined in (multiple)config file: kubectl delete -f config1.yaml -f config2.yaml

• To update objects by overriding (multiple)live configuration: kubectl replace -f config1.yaml -f config2.yaml

• To delete pod/deploy/svc by name: kubectl delete deploy/pod/svc <name>

• To check logs for a given pod: kubectl logs <pod-name>

• To list out all pods, services, deployments: kubectl get pods,deploy,svc

• To list out all pods, services, deployments for a given metadata label with key app:

  • run kubectl get pods,deploy,svc -l app=<your-app-name> or
  • run kubectl get pods,deploy,svc -l 'app in (<your-app-name>)'
  • more info: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/

• To scale any deployment by name: kubectl scale deployment/<deployment-name> --replicas=5

• To check if a deployment is working successfully or not:

  • run kubectl get pods
  • run kubectl exec -it <pod-name> sh
  • run nc -zv localhost:<container-port-number-of-the-pod> => this should be success confirming that the pod is running as expected.

• To start/pause/stop microk8s, run microk8s start/pause/stop.

• To start minikube with proper resources: minikube start --cpus 4 --memory 4096. This will start minikube with 4cpus and 4gb of ram.

• To manage multiple namespaces, install kubectx that provides a kubens tool to manage namespaces.

  • To list namespaces, run kubens.
  • To change namespace run kubens <your-namespace>.
  • To view all the components in the given namespace: kubectl get all -n <your-namespace>

• This will avoid headache of passing -n property to all kubectl commands for the selected namespace.