Basics

Command	Description
docker version	Display docker version of client and server
docker info	Display various docker information and configuration
docker	Display all available commands

New Management Command Line

docker <command> <sub-command> (options)

Command	Description
docker container run --publish 80:80 nginx	Create a NGINX container in the foreground
docker container run --publish 80:80 --detach nginx	Create a NGINX container in the background
docker container ls	List all active containers
docker container stop 7e4	Stop a container 7e4
docker container ls -a	List all containers (active and inactive)
docker container run --publish 80:80 --detach --name webhost nginx	Create a NGINX container with given name webhost
docker container logs webhost	Show logs of the container webhost
docker container top webhost	Display running processes of the container webhost
docker container --help	Display all container’s sub-commands
docker container rm 860 74e 957	Delete container 860, 74e, and 957 (non-active containers only)
docker container rm -f 860	Forced delete container 860 even it is running

What’s Happened?

1. Look for image locally
2. Look for image in remote repository (Docker Hub is the default repo)
3. Download the latest version by default
4. Create a new container and prepare to start
5. Give a virtual IP on a private network inside docker engine
6. Open port 80 on host and forward to port 80 in container
7. Start container by using the CMD in Dockerfile

Old Command Line

Command	Description
docker run --name mongo -d mongo	Create a new mongo DB container named mongo
docker ps	List all active containers
docker top mongo	Display running processes of the container mongo
docker stop mongo	Stop the container mongo
docker start mongo	Start the container mongo

Manage Multiple Containers

docker container run -d -p 3306:3306 --name db -e MYSQL_RANDOM_ROOT_PASSWORD=true mysql

Create a MySQL container

• in detach/background (-d) mode
• publish port 3306 on host to 3306 on container
• assign name db
• set environment variable MYSQL_RANDOM_ROOT_PASSWORD to true to generate root password and print out in the log

Command	Description
docker container run -d --name webserver -p 8080:80 httpd	Create a new HTTPd (Apache) container
docker container run -d --name proxy -p 80:80 nginx	Create a new NGINX container
docker container inspect mysql	See information on how the container mysql started in JSON format
docker container stats	See live stream of container statistics

Shell Inside Containers

docker container run -it --name proxy nginx bash

Create a new NGINX container named proxy and run bash command right after and keep terminal opened (-it.)
*Container will stop after exit

Ubuntu Container

docker container run -it --name ubuntu ubuntu

Try more commands:

apt-get update  
apt-get install -y curl  
curl google.com  

Command	Description
docker container start -ai ubuntu	Start the container ubuntu and open shell
docker container exec -it mysql bash	Create a new process and run bash inside container mysql
docker pull alpine	Pull the image alpine
docker image ls	List all local images
docker container run -it alpine sh	Create a new alpine container and open sh (bash is not available in alpine)
docker container run --rm -it centos:7	Create CentOS v7 container and open shell. Container is removed after exit.
docker container run --rm -it ubuntu	Create Ubuntu latest version and open shell. Container is removed after exit.

Docker Networking

Default Network

• Each container connected to a private virtual network ‘bridge’ or ‘docker0’
• Each virtual network routes through NAT firewall on host IP i.e. containers can goes out to the internet via the host machine
• All containers can talk to each other without -p
• Best practice is to create a new virtual network for each app (which may containing multiple containers)
• “Batteries includes, but removable”

Command	Description
docker container run -p 80:80 --name webhost -d nginx	Create a new NGINX container named webhost and map port 80—>80
docker container port webhost	See port mapping for container webhost
docker container inspect --format '' webhost	See IP address of the container webhost
ifconfig en0	See IP address of local machine
docker network ls	List all networks attached to Docker
docker network inspect bridge	See which containers attach to the network bridge

Creating a New Virtual Network

Command	Description
docker network create my_app_net	Create a new bridge network named my_app_net
docker container run -d --name new_nginx --network my_app_net nginx	Create a new container in the specified networt my_app_net
docker network connect webhost my_app_net	Connect container webhost to network my_app_net
docker container inspect webhost	See which network the container webhost connect to
docker network disconnect my_app_net webhost	Disconnect container webhost from network my_app_net

DNS

Because containers are always moving, come and go, all the times. Should not rely on IPs but names.

Command	Description
docker container run -d --name new_nginx --network my_app_net nginx:alpine	Create NGINX container named new_nginx and attach my_app_net
docker container run -d --name my_nginx --network my_app_net nginx:alpine	Create NGINX container named my_nginx and attach my_app_net
docker network inspect my_app_net	See both containers are attached to my_app_net
docker container exec -it my_nginx ping new_nginx	Ping new_nginx from my_nginx
docker container exec -it new_nginx ping my_nginx	Ping my_nginx from new_nginx

DNS Round Robin

Command	Description
docker network create dude	Create a new network named dude
docker container run -d --network dude --net-alias search elasticsearch:2	Create a new Elasticsearch container and attach to network dude with alias search
docker container run -d --network dude --net-alias search elasticsearch:2	Create another Elasticsearch container and attach to network dude with alias search
docker container run --rm --network dude alpine nslookup search	See NS entries mapped to DNS search
docker container run --rm --network dude centos:7 curl -s search:9200	Get Elastic search result from DNS search

Docker Image

Visit Docker Hub

Try to select image with more pulls and stars

Command	Description
docker pull centos	Download the latest (default) version of CentOS image
docker pull nginx:1.11	Download the version 1.11 of NGINX image
docker image ls	See all downloaded images

Official Images

• https://hub.docker.com/explore/
• https://github.com/docker-library/official-images/tree/master/library

Image Layer

• Docker always stores only one copy of an image layer.
• Image is checked via SHA hash for identical validation.
• When running a container, Docker create a R/W layer on top of an image

Command	Description
docker history nginx:latest	See history of image nginx:’latest
docker image inspect nginx	Display metadata of the image nginx e.g. exposed port, available environment variable, commands executed when a container is created

Image Tagging and Pushing

• Image can be uniquely referred by <user>/<image>:<tag>
• <user> is omitted for official images
• Tag is a label to image ID. One image ID can have many tags

Command	Description
docker image tag nginx pacroy/nginx	Create a new tag
docker image push pacroy/nginx	Upload tag to Docker Hub
cat .docker/config.json	See local Docker config
docker image tag pacroy/nginx pacroy/nginx:testing	Create another tag
docker image push pacroy/nginx:testing	Upload tag which layers already exist

Dockerfile

A recipe to create your own image.

Basic

Command	Description
FROM	Base image
WORKDIR	Works like cd
ENV	Key-value of environment variables
RUN	Commands to execute when building image *Use && to add more commands to make sure changes are put on the same layer
EXPOSE	Ports to expose
CMD	Commands to execute when running/starting container
COPY	Copy file from host into image

Docker Build

When rebuilding the image, only image layer that changed are rebuilt.

Command	Description
docker image build -t customnginx .	Build a new image tag customnginx from Dockerfile in current directory
docker image build -t nginx-with-html .	Build a new image tag nginx-with-html from Dockerfile in current directory
docker container run -p 80:80 --rm nginx-with-html	Run a container of the new image tag
docker image tag nginx-with-html:latest pacroy/nginx-with-html:latest	Re-tagging by creating a new tag

Dockerfile Exercise

# Instructions from the app developer
# - you should use the 'node' official image, with the alpine 6.x branch
FROM node:6-alpine

# - this app listens on port 3000, but the container should launch on port 80
#  so it will respond to http://localhost:80 on your computer
EXPOSE 3000

# - then it should use alpine package manager to install tini: 'apk add --update tini'
# - then it should create directory /usr/src/app for app files with 'mkdir -p /usr/src/app'
RUN apk add --update tini && \
    mkdir -p /usr/src/app

WORKDIR /usr/src/app

# - Node uses a "package manager", so it needs to copy in package.json file
COPY package.json package.json

# - then it needs to run 'npm install' to install dependencies from that file
# - to keep it clean and small, run 'npm cache clean --force' after above
RUN npm install && npm cache clean --force

# - then it needs to copy in all files from current directory
COPY . .

# - then it needs to start container with command 'tini -- node ./bin/www'
# - in the end you should be using FROM, RUN, WORKDIR, COPY, EXPOSE, and CMD commands
CMD [ "tini", "--", "node", "./bin/www" ]

Data Volume

VOLUME in Dockerfile

• Tells docker to create a new volume and mount at the specified location
• Can also be inspected (docker image inspect mysql)

Command	Description
docker container run -d --name mysql -e MYSEL_ALLOW_EMPTY_PASSWORD=true mysql	Create a new MySQL container
docker volume ls	List all created volumes
docker container inspect mysql	See which volume is mounted

Named Volume

Command	Description
docker container run -d --name mysql -e MYSEL_ALLOW_EMPTY_PASSWORD=true -v mysql-db:/var/lib/mysql mysql	Create a new MySQL container with named volume
docker container run -d --name mysql2 -e MYSEL_ALLOW_EMPTY_PASSWORD=true -v mysql-db:/var/lib/mysql mysql	Create another MySQL container using the same volume
docker volume create test-volume	Create a new volume named test-volume

Bind Mounting

• Two locations pointing to the same thing
• Can’t specified in Dockerfile
• Must be specified at docker run

Command	Description
docker container run -d --name nginx -p 80:80 -v $(pwd):/usr/share/nginx/html nginx	Create a new NGINX container with bind mount from current directory to /usr/share/nginx/html in the container
docker run -p 80:4000 -v $(pwd):/site bretfisher/jekyll-serve	Create a new Jekyll container with bind mount from current directory to /site

Useful Commands

Command	Description	Reference
uname -a	Print linux kernel version	whatsmyos.com
lsb_release -a	Print linux distro and version	askubuntu.com
cat /etc/*release	Print linux distro and version	whatsmyos.com
docker ps -a --filter volume=VOLUME_NAME_OR_MOUNT_POINT	Determine what containers use the docker volume
openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 30000 -nodes	Generate self-signed certificates	krishnasrinivas/wetty
ssh-keygen -t rsa -b 4096 -C “your_comment_or_email”	Generate SSH key	Connecting to GitHub with SSH

Useful Links

• How to Set Up Command Aliases in Linux/Ubuntu/Debian