Docker cheatsheet: Commands, Help and Tips

Docker Commands, Help & Tips #

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

Shorthand #

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

Naming Containers #

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

TIP: 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 container ls

$ docker ps

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]

TIP: 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)

TIP: 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 & PUSHING TO DOCKERHUB #

tags are labels that point ot an image ID

$ docker image ls

Youll see that each image has a tag

Retag existing image #

$ docker image tag nginx btraversy/nginx

Upload to dockerhub #

$ docker image push bradtraversy/nginx

If denied, do #

$ docker login

Add tag to new image #

$ docker image tag bradtraversy/nginx bradtraversy/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] .

TIP: 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 btraversy/nginx-website:latest

$ docker image push bradtraversy/nginx-website

VOLUMES #

Volume - Makes special location outside of container UFS. Used for databases #

Bind Mount -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

TIP: 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

Check volumes #

$ docker volume ls

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/brad/stuff:/path/container (mac/linux)
... run -v //c/Users/brad/stuff:/path/container (windows)

TIP: 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 exiost 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