Docker & Kubernetes

A walkthrough Docker&Kubernetes crash course with a summary of basic commands

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Resources

• Docker&Kubernetes-AraBigData
• AraBigData-Github

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Demo Project

A simple demo project to containerize a front-end application using dockerfile

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Getting Started

 docker image pull <image name>:<version>

by default if version not specified it would pull the latest version.

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 docker container create <argument> <image name> <command>
 docker container start <argument> <container id or name>

 docker container run <argument> <image>

'run' command can make up for three commands (image pull , create and start) as it pulls image(if not found locally) , create a new container and start container.

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To run executable(command) inside a running container

 docker exec -it <container> <command>
 docker exec -it nginx bash

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To stop container

 docker container stop <container id or container name>

To exit container without stopping

 Ctrl+p then ctrl+q  

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Listing commands

 docker image ls 
 docker container ls       #list running containers
 docker container ls --all #list all containers

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Remove & Delete

 docker container rm <container id>
 docker image rm <image name>
 docker container rm $(docker container ls -aq) -f    #remove all containers
 docker image rm $(docker image ls -q) -f             #remove all images

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Images-Deep dive

To pull unofficial image

  docker image pull <publisher>/<unofficial image name>:<version>

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To rename container and container hostname

  docker container run <argument> --name <new container name> -h <new container hostname> <image:version>
  docker container run -it --name alpine -h alp alpine 

So alpine linux container shell for example would look like [root@alp] on running instead of [root@2325f9e04787] and container name would be alpine instead of bla-bla names those made up by default.

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Images and Container metadata

 docker image inspect <image name or id>
 docker container inspect <container name or id>

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Docker Networking

Containers port mapping

 docker container run<argument> -p <host port>:<container port>
 docker container run -d --name webserver -p 80:80 nginx 

This would create a new container named webserver from nginx image with port mapping that container port 80 would redirect to port 80 on host.

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Copy files to containers

 docker container cp <file path> <container id or name>:<target path>
 docker container cp ./files/file.txt 87e:/tmp/file.txt

This would copy file.txt from host to /tmp/file.txt path on container with id 87e.

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Identifying other containers

 docker container run --add-host <container name or id>:<container ip> <image>
 docker container run --add-host web:172.17.0.2 ubuntu

-This would give container ubuntu ability to communicate another container named web which has ip 172.17.0.2 OR -from container ubuntu itself you can add web container to known hosts from /etc/hosts

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List docker networks

 docker network ls

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Network Types

• Bridge: creates a new adapter to bridge-connect created container
• Host: exposes the whole container to inherit container's host (simulates the host)
• None: creates an isolated container

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create container on network

 docker container run <argument> --network <network> image
 docker container run -it --network bridge alpine

by default network type is of type bridge in not given.

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Create new network

 docker network create <network name> -d <network type>
 docker network create mynet -d host

Create new network with specified subnet mask

 docker network create --subnet <netmask> <network name>
 docker network create --subnet 10.0.0.0/16 newnet

To create a new internal network (isolated)

 docker network create --internal  <network name>

To connect&disconnect container on specified network

 docker network connect <network> <container>
 docker network disconnect <network> <container>

Additional helpful commands

ip link show
ip addr show
ifconfig
curl

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Docker drivers

docker volumes info can be found on /var/lib/docker/overlay2 and volumes data in /var/lib/docker/volumes

Bind mount volume

 docker container run -it -v <path on host>:<path on container> <image>
 docker container run -it -v /files/pythonfiles:/app/code python

Create docker volume

 docker volume create <volume name>
 docker container run -it -v <volume name>:<path on container> <image>

 docker volume create myvol
 docker container run -it -v myvol:/app/code python 

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Build image

 docker commit <container name or id> <new image name>

Then you can build a new container with created image

New image name better be conventional to be able to push it docker hub or any cloud storage Like username/image name : version

Demo

 docker container run -it --name pyflask python bash
 docker commit pyflask DockerUser/pyflask:v1.0
 docker container run -d -p 5000:5000 --name pyf DockerUser/pyflask:v1.0 python /app/hello.py

Now a new container is built with name pyf you can find result from web browser on localhost:5000

create changes in file /app/hello.py after the first command in Demo to track changes and inheritance of layers for new image from old created container

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Dockerfile

Dockerfile cheat sheet

After Dockerfile creation build new image based on Dockerfile instructions

docker build -t <new image tag> <Dockerfile path>

Then you can casually create a container with newly made image.

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Image Registries

Login to dockerhub

docker login

rename (tag) image

docker tag <image> <new image tag>

New image tag better be conventional to be able to push it docker hub or any cloud storage Like username/image name : version

upload image to cloud storage

docker image push <image>

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Docker-compose

after Docker-compose installation

chmod +x /usr/local/bin/docker-compose

Build with docker-compose yaml file (docker-compose.yml)

• within context directory of docker-compose.yml file

docker-compose up &    #to run in background
#or in detatched mode
docker-compose up -d   #to run in detatched mode

it's better to run in background or with detatched mode to avoid that much of logs in your terminal

• if not in context directory of docker-compose yaml file

docker-compose -f <file_path>

List containers for a Compose project

docker-compose ps
docker-compose ps --all #list all containers, running and stopped

remove a compose project

docker-compose down

this would remove containers and networks of compose project but won't delete images and volumes

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Docker Swarm

initalize swarm

get your host ip address with "ifconfig" or whatever based on your os

docker swarm init --advertise-addr 'host ip address':2377 --listen-addr 'host ip address':2377

Show join token

docker swarm join-token worker   # worker node token
docker swarm join-token manager  # manager node token

Add nodes to swarm

on any other machine add a worker or a manager node based on the token

docker swarm join --token <token>

List swarm nodes

docker node ls

Create services on swarm

docker service create <options> <image>
docker service create --name web -p 80:80 --replicas 5 nginx:1.21

List swarm services

docker service ls

List service distribution on nodes

docker service ps <service>
docker service ps web

scaling service

docker service scale <service>=<number_of_replicas>
docker service scale  web=3

this would scale service up or down based on its origin set of replicas

Update service

docker service update --image <new_image> <options> <service>
docker service update --image nginx:latest --update-parallelism 2 --update-delay 5s web 

Delete service

docker service rm <service>
docker service rm web