Kubernetes

Minions = physical or virtual nodes Pods = A cluster of one or more containers. each pod has it's own IP but pods can share ports Labels = key/value pairs attached to any object in the system. Selectors = Queries that are made against labels. Controllers = Used in the management of the cluster. Controllers manage a set of Pods. Controllers use a YAML configuration file to maintain the desired state of the cluster. If a pod goes down the controller brings it up Services = Allows pods to work together

Service definitions are written in YAML.

Kubernetes Common Commands

man kubectl-get kubectl get nodes = show all nodes connected to master kubectl describe nodes kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="ExternalIP")].address}' kubectl get pods

Docker Common Commands

-i = interactive
-t = terminal
-d = daemonize (run in background)
-p = port local:remote (80:80)
- this allows us to map a random local port to an application specific port on the container. For example, if you want multiple containers running Apache or Nginx, you can assign arbitrary ports on the localhost to port 80 on the container. If we have 4 containers, we can have: - port 55000:80 on container1 - port 55001:80 on container2
- port 55002:80 on container3
- and so on. - u = user ID to connect to container as

docker pull ubuntu docker pull ubuntu:xenial docker run -i -t ubuntu /bin/bash docker run -itd ubuntu /bin/bash docker inspect ubuntu docker images docker attach docker ps = show all docker processes docker logs = show logs for container

Getting Started

Install and Enable NTP

$ yum -y install chronyd
$ systemctl enable chronyd

Set up the Docker Repo

Create the docker repo in /etc/yum.repos.d/

$ vim /etc/yum.repos.d/docker.repo

[virt7-docker-common-release]
name=virt7-docker-common-release
baseurl=http://cbs.centos.org/repos/virt7-docker-common-release/x86_64/os/
gpgcheck=0

Download a docker Ruby container:
$ docker pull training/sinatra

Launch that container interactively with a bash shell:
$ docker run -it training/sinatra /bin/bash

Exit the container and look at all docker containers on the system:
$ docker ps -a

Removing a docker image:
$ docker rmi <image id>

The Dockerfile

A Dockerfile is the main configuration file for creating a custom Docker image. Example:

$ vim dockerfile

# Dockerfile based on the latest CentOS 7 image - non privileged
FROM centos:latest
MAINTAINER tizitomm@gmail.com
RUN useradd -ms thn16
USER thn16

Build a Docker image using the Dockerfile we created:
$ docker build -t centos7/nonroot:v1 dockerfile

Connect to your Docker container as the container's root user:
$ docker exec -u 0 -it <container_name> /bin/bash

Kubernetes

https://linuxacademy.com/cp/socialize/index/type/community_post/id/15747

Configuring a Pod

Our configuration is a .YAML or .json file that will define the desired state of the Pod. This is how Kubernetes manages the Pods - when a Pod is no longer in the desired state Kubernetes will automatically make adjustments to the cluster to bring it to the desired state.

Various configuration settings: - apiVersion: the Kubernetes API version our file is using. - kind: The type of configuration this is (Pod) - metadata: Data about the Pod

Create a configuration file for nginx:
$ vim nginx.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.7.9
    ports:
    - containerPort: 80  

Launch a Pod

Using our "nginx.yaml" Pod configuration, use kubectl to launch a pod:
$ kubectl create -f ./nginx.yaml