Docker Quick-start Guide

To setup an instance to use docker, lets start with an Ubuntu server

sudo apt-get update

sudo apt-get -y install apt-transport-https ca-certificates curl gnupg-agent software-properties-common

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

sudo apt-get update

sudo apt-get install -y docker-ce=5:18.09.5~3-0~ubuntu-bionic docker-ce-cli=5:18.09.5~3-0~ubuntu-bionic containerd.io

sudo docker version

Give your own user access to run docker commands by adding it to docker group

sudo usermod -a -G docker ubuntu

Log out of the server, then log back in.

Once you are logged back on, you can verify cloud-user's access:

docker version

Set the log driver to syslog

Edit daemon.json:

sudo vi /etc/docker/daemon.json Add configuration to daemon.json to set the default logging driver.

{ "log-driver": "syslog" }

Restart docker.

sudo systemctl restart docker

Verify that the logging driver was set properly like so:

docker info | grep Logging

This command should return a line that says:

Logging Driver: syslog

Configure the swarm manager.

On the swarm manager server, initialize the swarm. Be sure to replace in this command with the actual Private IP of the swarm manager (NOT the public IP).

docker swarm init --advertise-addr <swarm manager private IP>;

Join the worker nodes to the cluster.

On the swarm manager, get a join command with a token:

docker swarm join-token worker This should provide a command that begins docker swarm join .... Copy that command and run it on both worker servers.

Go back to the swarm manager and list the nodes.

docker node ls Verify that you can see all three servers listed (including the manager). All three should have a status of READY. Once all three servers are ready, you have built your own Docker swarm cluster!

Managing Images

Download an image from a remote registry docker image pull nginx:1.14.0

To list your images docker image ls

To get more details about each image

docker inspect nginx

When you delete an image, that is associated with a container you are left with a dangling

docker image prune

Docker Registries

A docker registry is responsible for storing and distributing docker images. The default public registry for images is Docker Hub. But you can also create your own public/private registries and pull images from there.

Docker Services

Create a simple service running the nginx image.

docker service create nginx

Create an nginx service with a specified name, multiple replicas, and a published port.

docker service create --name nginx --replicas 3 -p 8080:80 nginx

Use a template to pass the node hostname to each container as an environment variable.

docker service create --name node-hostname --replicas 3 --env NODE_HOSTNAME="{{.Node.Hostname}}" nginx

Get the container running on the current machine, and print its environment variables to verify that the NODE_HOSTNAME variable is set properly.

docker exec <CONTAINER_ID> printenv

List the services in the cluster.

docker service ls

List the tasks for a service.

docker service ps nginx

Inspect a service.

docker service inspect nginx docker service inspect --pretty nginx

Change a service.

docker service update --replicas 2 nginx

Delete a service.

docker service rm nginx

Create a global service.

docker service create --name nginx --mode global nginx Two different ways to scale a service:

docker service update --replicas 3 nginx OR docker service scale nginx=4

Docker Compose

Install Docker Compose.

sudo curl -L "https://github.com/docker/compose/releases/download/1.24.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

sudo chmod +x /usr/local/bin/docker-compose

docker-compose version

Set up a Docker Compose project.

cd nginx-compose
vi docker-compose.yml

Create your docker-compose.yml.

version: '3'
services:
  web:
    image: nginx
    ports:
    - "8080:80"
  redis:
    image: redis:alpine

Start your Compose app.

docker-compose up -d List the Docker Compose containers, then stop the app.

docker-compose ps

docker-compose down