Docker

Docker

https://docker.io

https://hub.docker.io

Docker-cheat-sheet.pdf

Remote Docker Engine (aka containers running on a remote host)

docker -H=remote-docker-engine:2375 run nginx

Training

https://www.youtube.com/watch?v=fqMOX6JJhGo https://www.freecodecamp.org/ https://www.youtube.com/channel/UC8butISFwT-Wl7EV0hUK0BQ https://kodekloud.com/p/docker-labs

Containers

List running containers

docker ps

List all containers

docker ps -a

Run a container

docker run [image] [command]
-d detached
-i interactive
-t terminal  (usually -it)
-e VAR=value  (environment variables)
-v VOLUME_NAME:/container/mount/point
--entrypoint=sleep [image] [attribute]
--name name
--network network_name
--link real_container_name:target_name  (adds entries to /etc/hosts)   <-- Depreciated 

run:version (using a tag)

Stop a container

docker stop [name]/[id]

Port mapping

-p (host/external):(container/internal)

Directory mapping

-v /host/dir:/container/dir

Inspect (returns json)

docker inspect [container]

Images

List images

docker image ls

Remove image (must have no containers attached)

docker rmi [image]

Repository

Docker Hub

Assumes docker.io

image: nginx/nginx account/image <-- if nginx is specified it uses that as the username/account name also

Private Registry

docker login private-registry.io
docker run private-registry.io/apps/internal-app

Deploy Private Registry

docker run -d -p 5000:5000 --name registry registry:2
docker image tag my-image localhost:5000/my-image
docker push localhost:5000/my-image
docker pull localhost:5000/my-image

Dockerfile

Contains Instructions or Arguments

CMD can be as per cli or in json format

CMD command param1
CMD ["command","param1"]

FROM ubuntu:18.04
COPY . /app
ADD root/bashrc /root/.bashrc
ENV HOME /root
WORKDIR /root
RUN make /app
CMD python /app/app.py

Build

docker build [path/Dockerfilefolder]
-t name:tag

Create a Ubuntu container that sleeps for 5 seconds before exiting Dockerfile

From Ubuntu
CMD sleep 5

docker build -t ubuntu-sleeper .
docker run ubuntu-sleeper

Dockerfile

From Ubuntu
ENTRYPOINT ["sleep"]
CMD ["5"]             (becomes the default)

docker build -t ubuntu-sleeper .
docker run ubuntu-sleeper 10

Networks

docker network ls

Containers can resolve containers by name in the same network (internal dns server 127.0.0.11)

Create a network

docker network create --driver bridge --subnet 182.18.0.0/16 custom-isolated-network

Bridge

Internal network common to all docker containers in 172.17.0.0/24 network

None

Containers are isolated. Containers are not connected to any network

Host

Container runs directly on the host network.

Storage

Default storage

/var/lib/docker

Create volume

docker volume create data_volume  (generated /var/lib/docker/volumes/data_volume

Use Volume

docker run --mount data_volume:/var/lib/mysql mysql

Bind Mounting (with new syntax)

 docker run --mount type=bind,source=/host/data/mysql,target=/var/lib/mysql mysql

Compose

Yaml - run multiple containers together on a single Docker Host.

docker compose up

/blah/application/docker-compose.yml

version: 2
services:
  db:
    environment:
      POSTGRES_PASSWORD: mysecretpassword
    image: postgres
  wordpress:
    image: wordpress
    links:
    - db
    ports:
    - 8085:80
version: '3.0'

replace image with build (and path) to use local built images

Start

docker-compose up

Versions of docker-compose files (supports all)

• Version 1 - can not specify order or networks (all bridge and then links)
• Version 2 - starts with services: at the start, and version: 2 (all in bridge network, no need to use links), also has depends on feature
• version 3 - supports docker swarm

version: 2
services:
  redis:
    image: redis
    ...
    neworks:
      - back-end
  vote:
    image: voting-app
    networks:
      - front-end
      - back-end
networks:
  front-end:
  back-end:

Engine - Resources - cgroups

Control Groups

docker run --cpus=.5 ubuntu   <-- limit to max 50%
docker run --memory=100m ubuntu <-- limit to 100MB

Docker Swarm

H/A and distribution across multiple hosts Swarm Manager 1 --> n Workers (Nodes)