sridhar-sp/docker-demo

Sample project created to play with docker

docker-demo

Sample project created to play with docker

Docker

Basic commands

Run

docker run nginx

• Run the cached version of nginx if avaialble, otherwise docker will download the image from docker hub and run
• By default the run command will run in attached mode all the output stream data is sent to the caller (ex terminal)

Run specific version

docker run ubuntu:16:05

Run with name

docker run --name 'container_name' 'image_name'

Run and append a command

docker run ubuntu sleep 5

docker run -it ubuntu bash

Run in detached mode

docker run -d "name"

Attach to the already running container

docker attach 'container_id'

List containers

docker ps  // List all running containers
docker ps -a // List all containers

Execute a command in running container

docker exec 'container_id' 'command_to_execute'

Stop container

docker stop 'container_name'
docker stop 'container_1_name' 'container_2_name' ... 'container_n_name'

docker stop 'container_id'
docker stop 'container_1_id' 'container_2_id' ... 'container_n_id'

Remove container

docker rm 'container_name'
docker rm 'container_1_name' 'container_2_name' ... 'container_n_name'

docker rm 'container_1_id' 'container_2_id' ... 'container_n_id'

Note: Cannot remove a running container, should stop the container before removing

List docker images

docker images

Remove docker image

docker rmi 'image_name'

docker rmi 'image_id'

docker rmi 'image_1_id' 'image_2_id' ... 'image_n_id'

Note: Remove all container referring the image, before deleting an image

Download docker images

docker pull 'image_name'

Port mapping

docker run -p 'docker_host_port':'docker_container_app_port' 'container_name'

docker run -p 80:8080 app-name

Volume mapping

docker run -v 'docker_host_dir':'docker_container_dir' 'container_name'

docker run -v /opt/datadir:/var/lib/mysql mysql

Inspect container

docker inspect 'container_name'

Logs

docker logs 'container_name'

Dockerfile

FROM UBUNTU
RUN apt-get update && apt-get -y install python
RUN pip install flask
COPY  .  /opt/flask-app
ENTRYPOINT FLASK_APP = /opt/flask-app/app.py flask run

History

docker history 'container_name'

Command

CMD placed at the end of the docker file will be executed when running the docker image

File ubuntu_custom (docker file)

FROM ubuntu

CMD cat /etc/*-release

build & run using following command

docker build -t ubuntu_cmd .
docker run ubuntu_cmd

When run the above docker image, release information of the ubuntu distribution will be displayed on terminal

CMD can be replaced when running the image also

docker run ubuntu_cmd sleep 5

CMD syntax

CMD ["executable","param1","param2"]
CMD "executable param1 param2"

In the above case instead of printing release information the os sleeps for 5 seconds then exit

Entrypoint

Entrypoint instruction, similar to CMD, but it can't be replaced by the command-line parameter instead any additional command-line parameters will get appended to the entry point

FROM ubuntu

ENTRYPOINT ["cat"]

CMD ["/etc/adduser.conf"]

Build & run

docker build -t print_file .

docker  run print_file //No cmd-line argument, print /etc/adduser.conf

docker run print_file /etc/*-release // Print /etc/*-release

Entrypoint syntax

ENTRYPOINT ["executable", "param1", "param2"]
ENTRYPOINT command param1 param2

Docker compose

Example compose. app is dependent on redis

version: "3"
services:
  redis:
    image: "redis"
    ports:
      - 6379:6379

  app:
    build: .
    ports:
      - 3000:8080
    links:
      - redis
    environment:
      - REDIS_URL=redis://redis
    depends_on:
      - redis

Links

Example to link Redis to application

docker run --name 'app_name' --link redis:redis -p 3000:8080 --env=REDIS_URL=redis://redis "app_image_name"

Storage

Volume mapping

docker run -v 'host dir abs path':'dir used by the image'  'image name'

Networking

Default network

Network	Description
Bridge	Default private network all containers are attached to when no network is specified
Host	Use host network directly, no isolation between container and docker host
None	Disable all networking

User defined network

docker network create --driver 'network type' --subnet 'subnet_value' --gateway 'gateway_ip' 'user defined network name'
docker network create --driver bridge --subnet 182.18.0.1/24 --gateway 182.18.0.1 wp-mysql-network