Docker Cheat Sheet

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References
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Docker Engine -- runtime and ops https://docs.docker.com/engine/
Create Docker Containers -- build your own https://docs.docker.com/build/
Orchestrate Containers -- combine containers https://docs.docker.com/compose/

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Basic Docker - Overview
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Basic Docker Architecture

• Image as container - Binary images of s/w systems published as Containers
• Versioned - Containers are versioned
• Decentralized - Your server downloads/stores containers and their parents...warning, this gets large!

Basic Docker Lifecycle

• Pull containers to use or extend
• Run containers and expose local resources to them
• Extend existing containers to create custom run-anywhere binaries

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Basic Docker - Setup
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Install
sudo apt install docker.io
sudo apt install docker-compose

Running without sudo
Assign your user into the docker group. Add group if necessary.

sudo groupadd docker
sudo usermod -a -G docker myuser
# refresh groups or restart server

Other post-install tasks
See https://docs.docker.com/install/linux/linux-postinstall/

Configure - start on boot
On CentOS:
sudo systemctl [enable|disable] docker

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Docker service
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Starting the daemon
sudo service docker start

Start/Stop Docker Service
Debian:

sudo service docker start
CentOS:
sudo systemctl [start|stop] docker 

Test Docker Service
sudo docker run hello-world

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Managing Images
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List all Images
docker images

Image Info - i.e. How do I use this image?
docker image inspect <imageid>

Rename Image...by aliasing the image
docker tag <imageid> <alias>

Remove Image (untagging)
docker rmi <alias>

Remove Unused Images

docker image prune [-a]

Move docker image location off to another drive (for large files)

sudo service docker stop
ps faux|grep docker
sudo ls /var/lib/docker
mv /var/lib/docker <new location> 
sudo service docker start

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Running Containers
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See running containers

docker ps

Launch container from image
docker run -it [-d] [--rm] [--network <name>]  <image_id> 

where:
-d starts detached (daemon)
--rm removes on exit
--network network name to use (see `docker network ls`)

Retain image changes
docker commit <container_id> <group>/<alias>

Attach and execute shell
docker exec -it <container_id> bash

Build image from local Dockerfile
docker build . -t <alias>

Attach to running shell
docker attach <container_id>

Drop out of running shell - but leave running

ctl-p ctl-d

View container logging

docker logs <container_id>

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Creating Images
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Create a Dockerfile with a base image

Search DockerHub for a suitable base
FROM python:latest

Add some standard labels

LABEL org.opencontainers.image.title="Data Service" \

      org.opencontainers.image.version="0.0.1" \

      org.opencontainers.image.authors="aaa@baz.com,bbb@baz.com"

Add some content

ADD data-svc/ /home/python/data-svc/.

Open port for web service

EXPOSE 8080

Attach volumes for in/out of data

VOLUME ["/home/python/data", "/var/log/data-svc"]

Launch a service on container start

ENTRYPOINT ["flask", "--app", "data-svc", "run"]

Build the Docker Image

From the directory containing Dockerfile...

docker build -t <group>/<artifact>:<version> .

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Docker and Docker-Compose Runtime
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Start docker-compose containers
docker-compose up -d