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DOCKER.txt
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DOCKER.txt
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##############
### Docker ###
##############
https://www.youtube.com/watch?v=bhBSlnQcq2k&t=3476s
###Docker =>
Run container in seconds (instead of minutes)
Less resources (space and memory)
Does not need full OS
Infrastructure => Host Operating System => Docker => Apps A,B,C,D,E,F
###Virtual Machine =>
Infratructure => Hypervisor => every Apps needs Guest Operating System
###Image =>
template for creating an environment of your choice
snapshot
has everything to run your apps
os, software, app code
###Container =>
running instance of an image
Download Images from: https://hub.docker.com/
###Commands
docker --version => show docker version
docker pull nginx => load nginx image
Status: Downloaded newer image for nginx:latest
=> nginx:latest is the image
=> :latest is the tag of the image
docker xyz --help => information about a command
docker images => show images (repo-name, tag, image id, created, size)
docker image ls => alternative to show the images
docker run nginx:latest => start a container (instance) of the image
docker container ls => show the running containers (conainter, image, command, created, status, ports)
docker run -d nginx:latest => start a container in detached mode (same cmd-window can be used)
docker ps => show running container (second, faster method)
docker stop <container ID> => stop running the container (by container id)
docker stop <container Name> => stop running the container (by container name)
docker run -d -p 8080:80 nginx:latest => start containe and map localhost:8080 to port 80
=> typing localhost:8080 in the browser will connect to the nginx webserver running on port 80
docker run -d -p 8080:80 -p 3000:80 nginx:latest
=> start container and map localhost:8080 and localhost:3000 to port 80
docker start <container ID> => start running the container (by container id)
docker start <container Name> => start running the container (by container name)
docker inspect <container ID or NAME> => show informations about the container / image (per id or name)
docker logs <container ID or NAME> => show log for the container (per id or name)
docker ps -a => see all containers (running and not running)
docker rm <container ID or NAME> => delete a container (per id or name)
docker ps -aq => see all containers (but only the container ids)
docker rm $(docker ps -aq) => delete all (inactive container) - if container is running there will be an error
docker rm -f $(docker ps -aq) => delete all container (inactive and running) - in windows only working in powerhsell (not cmd)
docker run --name website -d -p 3000:80 nginx:latest
=> start the container and name it as "website"
docker start website / docker stop webiste
=> now the name can be used for starting and stoping the containers
###Volumes =>
Allows sharing of data between host<=>container and container <=> container
###Example for sharing volume between host and container:
docker run --name website -v c:/TEMP/website:/usr/share/nginx/html:ro -d -p 8080:80 nginx
=> create container with volume from c:/TEMP/website to the container volume in :ro (read-only mode)
=> when there is a html-file in c:/TEMP/website then it will be displayed in the container under localhost:8080
=> all changes which are done on the file in windows are automatically reflected also in the container cause they are mounted
docker run --name website -v c:/TEMP/website:/usr/share/nginx/html -d -p 8080:80 nginx
=> without the :ro command the volume is mounted also for read / write
=> so it is also possible that there are changes directly on the container volume - which are reflected to the (windows)-host
###Example for sharing a volume between 2 containers:
docker run --name website-copy --volumes-from website -d -p 8081:80 nginx
=> first container is the previous container website on port 8080:80
=> second container is the website-copy on port 8081:80
###Dockerfile =>
to build own images
Docu: https://docs.docker.com/engine/reference/builder/
Creating a file "Dockerfile"
FROM nginx:latest => template / existing docker images as basis
ADD . /usr/share/nginx/html => add all files in this path
docker build --tag website:latest . => build an image (name "website", version "latest", use actual folder with "." where the docker file is)
2 Steps are done (commands from the Dockerfile)
=> [1/2] FROM docker.io/library/nginx:latest 0.1s
=> [2/2] ADD . /usr/share/nginx/html
docker image ls => shows now 2 images (1x the previous "nginx" and 1x the new "website")
docker run --name website -p 8080:80 -d website:latest
=> start the container from the new build image "website:latest"
###Image from an API
Install https://nodejs.org/en/ and http://expressjs.com/
Create folder eg. user-service-api
npm install --save expressjs => install expressjs
Create index.js and copy the example Hello World from expressjs.com/
node index.js => start listening on port 3000 (or in IDEA)
localhost:3000 => shows "Hello World" in the browser
create dockerfile "Dockerfile" with content:
FROM node:latest
WORKDIR /APP => creating the APP directory if it not exits
ADD . . => ADD everything from the local machine to the container
RUN npm install => install dependencies
CMD node index.js => command which should be executed
Image "user-service-api" created
###.dockerignore
create this file for ignoring folder and files
=> node_modules => ignore folder or files which the docker-image not need
=> Dockerfile => ignore the Dockerfile
*.xyz.js => ignore files which ending with xyz.js
folder/** => ignore folder
###Reduce image space with alpine versions
reduce the filesize using the "alpine"-file version of the image
docker pull node:lts-alpine => pull docker image with lts-apline tag (lts for latest)
with this alpine version / tag we can save a huge amount of space for the image
node: has only 117MB (900MB full version)
nginx: has only 21,8MB (133MB before)
###Tag, Versioning and Tagging
Allows you to control image version
Avoid breaking changes
Using the latest version is sometimes dangerous (takes allways the last version - sometimes this could not work with your code)
docker tag amigoscode-website:latest amigoscode-website:1
=> tag the repo "amigoscode-website" with tag "1"
###Docker Registries
stores images - server holds the images
push => takes images to the registry
registry could be private or publich (like github)
=> Docker Hub
=> quay.io/library/nginx
=> Amazon ECR
example: https://hub.docker.com/repository/docker/rapid1898/website
###Kubernetes
Orchestration Tool for docker images / containers
Trend from Monolith to Microservices - incread usage of conatainers
offerings from Kubernetes
=> high availailibility / no downtime
=> scalability / high performance
=> disaster recovery / backup and restore
Architecture
=> 1 Master Node (has a API server, Controller Manager, Scheduler - has a UI, API, CLI)
(backup of the master is absolute necessary - normally at least 2 instances of the master which can be switched at any time)
=> many Worker Nodes (different docker containers on the nodes - one or many)
=> Virtual Network - communication between Worker Nodes and Master Node (creates an unfified machine)