Docker basics

Installation

[On Ubuntu 14.04] Installation:

sudo apt-get update
sudo apt-get install -y docker.io
sudo ln -sf /usr/bin/docker.io /usr/local/bin/docker
sudo sed -i '$acomplete -F _docker docker' /etc/bash_completion.d/docker.io

Last version installation:

wget -qO- https://get.docker.io/gpg | sudo apt-key add -
sudo sh -c "echo deb http://get.docker.io/ubuntu docker main > /etc/apt/sources.list.d/docker.list"
sudo apt-get update
sudo apt-get install lxc-docker -y

Removing sudo for commands

I order to avoid ‘sudo’ prefix in all docker commands, here I write a tip for removing sudo from all Docker commands:

# Add the docker group
sudo groupadd docker
 
# Add the connected user "${USERNAME}" to the docker group.
sudo gpasswd -a ${USERNAME} docker
# Logout/Login with this user for changes to take effect
 
# Restart the docker daemon.
sudo service docker.io restart

Run your first container

Docker Hub is the big repo of images. You can login by ‘docker login’

Download image and run container console:

docker run -t -i ubuntu:14.04 /bin/bash
root@af8bae53bdd3:/# pwd
/
root@af8bae53bdd3:/# exit

Basic operations

Operations with Containers:

• ‘docker ps [-a] CONTAINER’ containers running (-a shows all including stopped)
• ‘docker logs -f CONTAINER’ container standard output
• ‘docker top CONTAINER’ container processes running list
• ‘docker inspect CONTAINER’ container low level json report
• ‘docker stop CONTAINER’ stops the container
• ‘docker start CONTAINER’ restarts a container previously stopped
• ‘docker rm [-f] CONTAINER’ removes definitely a container previously stopped. ‘docker rm -f $(docker ps -a -q)’ removes all containers.

Operations with images:

• ‘docker images’ list images in workstation
• ‘docker search TERM’ search images (look at Docker Hub)
• ‘docker tag [ID] [NAME]:[TAG]’ tags an image
• ‘docker push [NAME]’ upload image to Docker.hub
• ‘docker rmi [NAME]’ locally removes an image

Create an Image

mkdir ubuntu-chef
cd ubuntu-chef
touch Dockerfile

And write it:

# Ubuntu + chef-solo
FROM ubuntu:14.04
MAINTAINER Juan Lebrijo "juan@lebrijo.com"

RUN apt-get -y update
RUN apt-get -y install curl build-essential libxml2-dev libxslt-dev git
RUN curl -L https://www.opscode.com/chef/install.sh | bash

Operations with Chef:

• ‘docker build -t jlebrijo/ubuntu-chef .’ creates an image
• docker run -d -m 8g –cpuset 0-7 –name rails_stack -p 2222:22 -i jlebrijo/trusty-chef
• knife solo cook root@localhost -p 2222
• ssh root@localhost -p 2222

Tricks

• Stopping all containers: docker stop $(docker ps -a -q)
• Removing all containers: docker rm $(docker ps -a -q)

Exposing a port on a live container

You need to create an image from your container and restart the container based on this image:

docker stop www
docker commit www www-image
docker rm www
docker run --detach=true --name www -p 2222:22 -p 80:80 -p 443:443 -p 9292:9292 www-image
docker rm www-image