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Docker Commands & Tips

Table of Contents

Docker Basics

Show commands & management commands:

$ docker

Docker version info:

$ docker version

Show info like number of containers, etc:

$ docker info

Working with Containers

Create an run a container in foreground:

$ docker container run -it -p 80:80 nginx

Create an run a container in background:

$ docker container run -d -p 80:80 nginx

Naming Containers:

$ docker container run -d -p 80:80 --name nginx-server nginx

Tips: What Run Did:

  • Looked for image called nginx in image cache
  • If not found in cache, it looks to the default image repo on Dockerhub
  • Pulled it down (latest version), stored in the image cache
  • Started it in a new container
  • We specified to take port 80- on the host and forward to port 80 on the container
  • We could do "$ docker container run --publish 8000:80 --detach nginx" to use port 8000
  • We can specify versions like "nginx:1.09"

List running containers:

$ docker ps # docker container ls

List all containers (Even if not running):

$ docker container ls -a

Stop container:

$ docker container stop [ID]

Stop all running containers:

$ docker stop $(docker ps -aq)

Remove container (Can not remove running containers, must stop first):

$ docker container rm [ID]

To remove a running container use force(-f):

$ docker container rm -f [ID]

Remove multiple containers:

$ docker container rm [ID] [ID] [ID]

Remove all containers:

$ docker rm $(docker ps -aq)

Get logs (Use name or ID):

$ docker container logs [NAME]

List processes running in container:

$ docker container top [NAME]

Tips: About Containers

Docker containers are often compared to virtual machines but they are actually just processes running on your host os. In Windows/Mac, Docker runs in a mini-VM so to see the processes youll need to connect directly to that. On Linux however you can run "ps aux" and see the processes directly

Image Commands

List the images we have pulled:

$ docker image ls

We can also just pull down images:

$ docker pull [IMAGE]

Remove image:

$ docker image rm [IMAGE]

Remove all images:

$ docker rmi $(docker images -a -q)

Tips: About Images

  • Images are app bianaries and dependencies with meta data about the image data and how to run the image
  • Images are no a complete OS. No kernel, kernel modules (drivers)
  • Host provides the kernel, big difference between VM

Some sample container creation

Nginx:

$ docker container run -d -p 80:80 --name nginx nginx (-p 80:80 is optional as it runs on 80 by default)

Apache:

$ docker container run -d -p 8080:80 --name apache httpd

MongoDB:

$ docker container run -d -p 27017:27017 --name mongo mongo

MySQL:

$ docker container run -d -p 3306:3306 --name mysql --env MYSQL_ROOT_PASSWORD=123456 mysql

Container Info

View info on container:

$ docker container inspect [NAME]

Specific property (--format):

$ docker container inspect --format '{{ .NetworkSettings.IPAddress }}' [NAME]

Performance stats (cpu, mem, network, disk, etc):

$ docker container stats [NAME]

Accessing Containers

Create new nginx container and bash into:

$ docker container run -it --name [NAME] nginx bash
  • i = interactive Keep STDIN open if not attached
  • t = tty - Open prompt

For Git Bash, use "winpty"

$ winpty docker container run -it --name [NAME] nginx bash

Run/Create Ubuntu container:

$ docker container run -it --name ubuntu ubuntu

(no bash because ubuntu uses bash by default)

You can also make it so when you exit the container does not stay by using the -rm flag:

$ docker container run --rm -it --name [NAME] ubuntu

Access an already created container, start with -ai:

$ docker container start -ai ubuntu

Use exec to edit config, etc:

$ docker container exec -it mysql bash

Alpine is a very small Linux distro good for docker:

$ docker container run -it alpine sh

(use sh because it does not include bash)
(alpine uses apk for its package manager - can install bash if you want)

Networking

"bridge" or "docker0" is the default network

Get port:

$ docker container port [NAME]

List networks:

$ docker network ls

Inspect network:

$ docker network inspect [NETWORK_NAME]
("bridge" is default)

Create network:

$ docker network create [NETWORK_NAME]

Create container on network:

$ docker container run -d --name [NAME] --network [NETWORK_NAME] nginx

Connect existing container to network:

$ docker network connect [NETWORK_NAME] [CONTAINER_NAME]

Disconnect container from network:

$ docker network disconnect [NETWORK_NAME] [CONTAINER_NAME]

Detach network from container:

$ docker network disconnect

Image Tagging & Pushinh to Dockerhub

Tags are labels that point to an image ID:

$ docker image ls
# Youll see that each image has a tag

Retag existing image:

$ docker image tag nginx ggabiola/nginx

Upload to dockerhub:

$ docker image push genesisgabiola/nginx

If denied, do:

$ docker login

Add tag to new image:

$ docker image tag genesisgabiola/nginx genesisgabiola/nginx:testing

Dockerfile Parts:

  • FROM - The os used. Common is alpine, debian, ubuntu
  • ENV - Environment variables
  • RUN - Run commands/shell scripts, etc
  • EXPOSE - Ports to expose
  • CMD - Final command run when you launch a new container from image
  • WORKDIR - Sets working directory (also could use 'RUN cd /some/path')
  • COPY # Copies files from host to container

Build image from dockerfile (reponame can be whatever)

From the same directory as Dockerfile:

$ docker image build -t [REPONAME] .

Tips: Cache & Order

  • If you re-run the build, it will be quick because everythging is cached.
  • If you change one line and re-run, that line and everything after will not be cached
  • Keep things that change the most toward the bottom of the Dockerfile

Extending Dockerfile

Custom Dockerfile for html paqge with nginx:

FROM nginx:latest # Extends nginx so everything included in that image is included here
WORKDIR /usr/share/nginx/html
COPY index.html index.html

Build image from Dockerfile:

$ docker image build -t nginx-website

Running it:

$ docker container run -p 80:80 --rm nginx-website

Tag and push to Dockerhub:

$ docker image tag nginx-website:latest ggabiola/nginx-website:latest
$ docker image push genesisgabiola/nginx-website

Volumes

  • volumes makes special location outside of container UFS. Used for databases
  • bind mounts link container path to host path

Check volumes:

$ docker volume ls

Cleanup unused volumes:

$ docker volume prune

Pull down mysql image to test:

$ docker pull mysql

Inspect and see volume:

$ docker image inspect mysql

Run container:

$ docker container run -d --name mysql -e MYSQL_ALLOW_EMPTY_PASSWORD=True mysql

Inspect and see volume in container:

$ docker container inspect mysql

Tips: Mounts

  • You will also see the volume under mounts
  • Container gets its own uniqe location on the host to store that data
  • Source: xxx is where it lives on the host

There is no way to tell volumes apart for instance with 2 mysql containers, so we used named volumes

Named volumes (Add -v command)(the name here is mysql-db which could be anything):

$ docker container run -d --name mysql -e MYSQL_ALLOW_EMPTY_PASSWORD=True -v mysql-db:/var/lib/mysql mysql

Inspect new named volume:

docker volume inspect mysql-db

Bind Mounts

  • Can not use in Dockerfile, specified at run time (uses -v as well)
  • ... run -v /Users/<username>/stuff:/path/container (mac/linux)
  • ... run -v //c/Users/<username>/stuff:/path/container (windows)

Tips: Instead of typing out local path, for working directory use $(pwd):/path/container - On windows may not work unless you are in your users folder

Run and be able to edit index.html file (local dir should have the Dockerfile and the index.html):

$ docker container run  -p 80:80 -v $(pwd):/usr/share/nginx/html nginx

Go into the container and check:

$ docker container exec -it nginx bash
$ cd /usr/share/nginx/html
$ ls -al

You could create a file in the container and it will exist on the host as well:

$ touch test.txt

Docker Compose

  • Configure relationships between containers
  • Save our docker container run settings in easy to read file
  • 2 Parts: YAML File (docker.compose.yml) + CLI tool (docker-compose)

  1. docker.compose.yml - Describes solutions for:

    • containers
    • networks
    • volumes

  2. docker-compose CLI - used for local dev/test automation with YAML files

Sample compose file (From Bret Fishers course)

version: '2'

# same as
# docker run -p 80:4000 -v $(pwd):/site bretfisher/jekyll-serve

services:
  jekyll:
    image: bretfisher/jekyll-serve
    volumes:
      - .:/site
    ports:
      - '80:4000'

To run:

docker-compose up

You can run in background with:

docker-compose up -d

To cleanup:

docker-compose down

Wordpress & Docker

Setup Wordpress, MySQL & PHPMyAdmin with a single command. Add the code below to a file called "docker-compose.yaml" and run the command

$ docker-compose up -d

# To Tear Down
$ docker-compose down --volumes
version: '3'

services:
  # Database
  db:
    image: mysql:5.7
    volumes:
      - db_data:/var/lib/mysql
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: password
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress
    networks:
      - wpsite
  # phpmyadmin
  phpmyadmin:
    depends_on:
      - db
    image: phpmyadmin/phpmyadmin
    restart: always
    ports:
      - '8080:80'
    environment:
      PMA_HOST: db
      MYSQL_ROOT_PASSWORD: password 
    networks:
      - wpsite
  # Wordpress
  wordpress:
    depends_on:
      - db
    image: wordpress:latest
    ports:
      - '8000:80'
    restart: always
    volumes: ['./:/var/www/html']
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
    networks:
      - wpsite
networks:
  wpsite:
volumes:
  db_data: