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<!DOCTYPE html>
<html>
<head>
<title>An introduction to Docker</title>
<meta charset="utf-8">
<link rel="stylesheet" href="styles.css" />
<link rel="shortcut icon" href="media/favicon.png" type="image/png" />
</head>
<body>
<textarea id="source">
class: center, middle
# An introduction to
---
class: center, middle
# Courtesy of
---
# Agenda
.lhs[
* Intro and overview
* [Check your setup](#prep)
* [Hello world!](#hello-world)
* [Key concepts](#key-concepts)
* [Containers vs Virtual Machines](#containers-vs-vms)
* [The clever bits](#the-clever-bits)
* Images
* [Names and tags](#image-names-and-tags)
* [Building images](#building-images)
* [Publishing images](#publishing-images)
]
.rhs[
* Containers
* [Ports](#ports)
* [Environment variables](#environment)
* [Networks](#networks)
* [Volumes](#volumes)
* [Docker Compose](#compose)
]
---
name: prep
# Preparation
You will need **a good connection to the internet** during this setup, and
(to some extent) while going through the course, as we'll be installing
software, and downloading Docker "images".
It's useful to have **a local copy of these training materials**:
`git clone https://github.com/realestate-com-au/intro-to-docker.git`
You definitely need **Docker and Docker Compose**.<br/>
Installation intructions follow.
---
# Installing Docker
#### OS X
* Install [Docker for Mac](https://docs.docker.com/docker-for-mac/)
#### Windows
* Install [Docker for Windows](https://docs.docker.com/docker-for-windows/)
#### Linux
```
$ `curl -sSL https://get.docker.com/ | sh`
```
---
# Docker Engine
.center[
]
???
Docker only runs on Linux.
On OS X and Windows, it runs inside a VM.
---
# Check your setup
Let's check that everything is working:
```
$ `./setup.sh`
YAY: /var/run/docker.sock exists
YAY: I can talk to docker
Docker is at localhost
YAY: docker version 1.12.0
YAY: docker-compose version 1.8.0
Pulling some images to get you started ...
```
Not working? Ask for help!
.small.lhs[
Don't worry _too_ much if you get complaints about versions of `docker`
and `docker-compose`; _most_ things will still work.)
]
---
name: hello-world
# Try it: Hello world!
"Pull" an image:
```
$ `docker pull hello-world`
Using default tag: latest
latest: Pulling from library/hello-world
c04b14da8d14: Pull complete
Digest: sha256:0256e8a36e2070f7bf2d0b0763dbabdd67798512411de4cdcf9431a1feb60fd9
Status: Downloaded newer image for hello-world:latest
```
Run a container:
```
$ `docker run hello-world`
Hello from Docker.
…
```
---
name: key-concepts
# Key concepts
.lhs[
## "image"
* passive
* a file system snapshot
* similar to:
- Virtual Machine image
- AMI (Amazon Machine Image)
]
--
.rhs[
## "container"
* active
* a group of processes
* similar to:
- Virtual Machine
- EC2 instance
]
--
.center[
]
---
# Try it: different Linux distros
Run Ubuntu:
```
$ `docker run ubuntu dpkg -l`
```
or CentOS:
```
$ `docker run centos rpm -qa`
```
--
…
Speedy, huh?
---
# Try it: run a shell
```
$ `docker run -i -t ubuntu bash`
```
* `-i` = Keep STDIN open
* `-t` = Allocate a pseudo-TTY
Now, try doing an Ubuntu thing:
```
root@container# `apt-get update`
```
---
name: containers-vs-vms
# Containers vs. Virtualisation
.center[
]
???
With virtualisation, you have the added weight of a guest kernel.
With Docker, processes communicate directly with the host kernel.
---
# More containers vs. VMs
<table class="compare">
<tr>
<td></td>
<th>Virtual<br/>Machines</th>
<th>Docker</th>
</tr>
<tr>
<td class="factor">image size</td>
<td>Gigabytes</td>
<td>Megabytes</td>
</tr>
<tr>
<td class="factor">startup time</td>
<td>minutes</td>
<td>sub-second</td>
</tr>
<tr>
<td class="factor">Linux kernel is</td>
<td>separate</td>
<td>shared</td>
</tr>
<tr>
<td class="factor">isolation is</td>
<td>complete</td>
<td>pretty good</td>
</tr>
<tr>
<td class="factor">used to encapsulate</td>
<td>servers</td>
<td>services</td>
</tr>
</table>
---
# Try it: which kernel?
Run `uname -a` on both `ubuntu` and `centos`:
```
$ `docker run ubuntu uname -a`
$ `docker run centos uname -a`
```
Can you explain the result?
--
…
Different distros, same kernel: same result.
.center[
]
---
# Try it: overhead, much?
Use "time" to measure the overhead of running a command in a container.
```
$ `time docker run ubuntu bash -c "time sleep 1"`
```
How much time did Docker add?
---
name: the-clever-bits
class: center, middle, big
# The clever bits
Linux "cgroups" + "image" management =
---
# Linux "control groups"
.big.center["`chroot` on steroids"]
<br/>
Isolate processes by limiting access to:
- file system
- hardware resources
- other processes
Not a new idea:
* aka LXC
* project started by Google
* used extensively by PaaS such as Heroku
* similar to Solaris Zones, BSD Jails
---
# Union file systems
.lhs[
Images are made of "layers", and can **share** base layers.
Container root file system is just another (writable) layer.
Various drivers supported:
- aufs
- devicemapper
- btrfs
- overlay
- zfs
]
.rhs[
<table class="docker-image">
<tr><td class="writable">container root</td></tr>
<tr><td>↓</td></tr>
<tr><td class="snapshot">image layer</td></tr>
<tr><td>↓</td></tr>
<tr><td class="snapshot">image layer</td></tr>
<tr><td>↓</td></tr>
<tr><td class="snapshot">image layer</td></tr>
</table>
]
---
# Try it: test container file system isolation
Attempt to cripple your Ubuntu image:
```
$ `docker run -i -t ubuntu bash`
root@3256d8252fe6:/# `ls /usr/bin`
root@3256d8252fe6:/# `rm -fr /usr/bin`
root@3256d8252fe6:/# `ls /usr/bin`
^D
```
Now, start another container:
```
$ `docker run -i -t ubuntu bash`
root@3ed46bfba026:/# `ls /usr/bin`
```
---
# Try it: check out those layers
Use `docker history` to view image layers
```
$ `docker history ubuntu`
IMAGE CREATED CREATED BY
07c86167cdc4 2 days ago /bin/sh -c #(nop) CMD ["/bin
<missing> 2 days ago /bin/sh -c sed -i 's/^#\s*\(
<missing> 2 days ago /bin/sh -c echo '#!/bin/sh'
<missing> 2 days ago /bin/sh -c #(nop) ADD file:b
```
---
name: images
class: center, middle
# Images
---
name: image-names-and-tags
# Image names and tags
Image-name pattern:
.center[
`[[<REGISTRY>/]<NAMESPACE>/]<REPOSITORY>[:<TAG>]`
]
* `<REGISTRY>` defaults to `docker.io` ("official" registry)
* `<NAMESPACE>` defaults to `library`
* `<TAG>` defaults to `latest`
These are all equivalent:
```
$ `docker run hello-world`
$ `docker run hello-world:latest`
$ `docker run library/hello-world`
$ `docker run docker.io/library/hello-world:latest`
$ `docker run sha256:c54a2cc56cbb`
$ `docker run sha256:c54a2cc56cbb2f04003c1cd4507e118af7c0d340fe7e2720f70976c4b75237dc`
```
---
# Try it: investigate tags in the `ubuntu` repository
Run a command using `ubuntu:16.04`:
```
$ `docker run ubuntu:16.04 grep -v "^#" /etc/apt/sources.list`
```
Try the same thing using `ubuntu:14.04`:
```
$ `docker run ubuntu:14.04 grep -v "^#" /etc/apt/sources.list`
```
--
View images in the `ubuntu` repository:
```
$ `docker images ubuntu`
```
---
name: building-images
# Try it: build an image, the hard way
Install some software in an `ubuntu` container:
```
$ `docker run -i -t ubuntu bash`
root@f55393e5dc31:/# `apt-get update && apt-get install -y curl`
…
^D
```
Now, `commit` that container to create an image:
```
$ `docker commit f55393e5dc31 ubuntu-with-curl`
```
Check it out:
```
$ `docker history ubuntu-with-curl`
…
$ `docker run ubuntu-with-curl curl http://example.com`
```
---
# Layers, with labels
```
$ `docker history ubuntu-with-curl`
```
<table class="docker-image">
<tr>
<td class="snapshot">27323a7d221f</td>
<td class="labels">ubuntu-with-curl</td>
</tr>
<tr><td>↓</td></tr>
<tr>
<td class="snapshot">07c86167cdc4</td>
<td class="labels">ubuntu:latest</td>
</tr>
<tr><td>↓</td></tr>
<tr>
<td class="snapshot">...</td>
</tr>
<tr><td>↓</td></tr>
<tr>
<td class="snapshot">...</td>
</tr>
<tr><td>↓</td></tr>
<tr>
<td class="snapshot">...</td>
</tr>
</table>
---
# Try it: build an image, the easy way
Use a `Dockerfile`:
```
FROM ubuntu
RUN apt-get update && apt-get install -y curl
```
to build an image:
```
$ `docker build -t ubuntu-with-curl exercises/ubuntu-with-curl`
Sending build context to Docker daemon 2.048 kB
Step 1 : FROM ubuntu
---> 07c86167cdc4
Step 2 : RUN apt-get update && apt-get install -y curl
---> Running in 51bf195331b7
Ign http://archive.ubuntu.com trusty InRelease
Get:1 http://archive.ubuntu.com trusty-updates InRelease [64.4 kB]
…
---> 70b42c74bb66
Removing intermediate container 51bf195331b7
Successfully built 70b42c74bb66
```
---
# Try it: leverage the "build cache"
Use the recipe provided:
```
FROM node:6.2.2
COPY package.json /app/
WORKDIR /app
RUN npm install
COPY index.js /app/
ENV PORT 80
EXPOSE $PORT
CMD ["node", "/app/index.js"]
```
to build an image:
```
$ `docker build -t ciao exercises/ciao`
```
---
# Try it: invalidate the "build cache"
Build it again:
```
$ `docker build -t ciao exercises/ciao`
```
Faster, eh? Observe: "Using cache".
--
Make a change to `exercises/ciao/index.js`, then build again:
```
$ `docker build -t ciao exercises/ciao`
```
What happens at "Step 5"?
--
Now make a change to `exercises/ciao/package.json`, and build again.
```
$ `docker build -t ciao exercises/ciao`
```
What happens at "Step 4"?
---
name: publishing-images
# Publishing images
Sign up for an account at [`http://hub.docker.com`](http://hub.docker.com)
.center[
<img src="media/docker-hub.png" width="100%"/>
]
---
# Try it: push an image to Docker Hub
Authenticate to Docker Hub:
```
$ `docker login`
```
"Tag" an image into _your_ namespace:
```
$ `docker tag ciao YOURNAMEHERE/ciao`
```
Now you can push it:
```
$ `docker push YOURNAMEHERE/ciao`
```
---
# Try it: pull an image someone else pushed
Talk to the esteemed colleague next to you, and ask them
for their Docker Hub username. Then, you shoud be able to
fetch the image _they_ pushed.
```
$ `docker pull YOURNEIGHBOUR/ciao`
```
---
class: middle, center
# Containers
---
# Try it: container basics
Run a container as a daemon (in the background):
```
$ `docker run -d ciao`
```
List the running containers:
```
$ `docker ps`
```
List ALL the containers:
```
$ `docker ps -a`
```
Remove a container:
```
$ `docker rm <ID_OR_NAME>`
```
Remove a RUNNING container:
```
$ `docker rm -f <ID_OR_NAME>`
```
---
# Try it: name your containers
Start a container with a `--name`:
```
$ `docker run --name app ciao`
```
Now you can use the NAME rather than an ID:
```
$ `docker rm -f app`
```
---
name: ports
# Try it: map a port to a host port
```
$ `docker run -d --name app -p 5678:80 ciao`
```
.center[
<img src="diagrams/ciao-explicit-port.png" width=40% />
]
```
$ `curl localhost:5678`
```
Remember to clean up:
```
$ `docker rm -f app`
```
---
# Try it: use a random host port
If you don't specify a host port, Docker will choose one:
```
$ `docker run -d --name app -p 80 ciao`
```
.center[
<img src="diagrams/ciao-random-port.png" width=40% />
]
Use `docker port` to discover which one it chose:
```
$ `docker port app 80`
```
---
# Try it: logs
You can get the output using `docker logs`:
```
$ `docker logs app`
```
or even follow along in real time:
```
$ `docker logs --follow --timestamps app`
```
---
name: environment
# Try it: set environment variables
Assuming your application looks for environment variables, e.g.
```javascript
var MESSAGE = (process.env.MESSAGE || "Ciao mondo.");
```
You can set them to provide configuration:
```
$ `docker run -d --name app -p 5678:80 -e MESSAGE='Hey, guys!' ciao`
```
Test the result:
```
$ `curl localhost:5678`
```
---
name: networks
class: middle, center
# Networks
---
# Consider: a reverse-proxy image
```
upstream backend {
server ${BACKEND:-"app"} fail_timeout=0;
}
server {
listen ${PORT:-80};
location / {
proxy_pass http://backend;
}
}
```
---
# Try it: inter-container networking
Create a "network":
```
$ `docker network create shared`
$ `docker network ls`
```
Attach some containers:
```
$ `docker rm -f app proxy`
$ `docker run -d --net=shared --name app \`
`realestate/ciao`
$ `docker run -d --net=shared --name proxy \`
`-p 5678:1234 -e PORT=1234 -e BACKEND=app \`
`realestate/ciao-proxy`
```
```
$ `curl -si localhost:5678`
```
---
class: center, middle
<img src="diagrams/shared-network.png" width="60%" />
---
name: volumes
class: middle, center
# Volumes
---
# Try it: volume from host
Mount your home directory from the "host":
```
$ `docker run -it --rm -v $HOME:/myhome ubuntu bash`
root@c10a43c38793:/# `mount | grep home`
root@c10a43c38793:/# `cd /myhome; ls`
root@c10a43c38793:/# `echo HELLO FROM DOCKER > written-from-docker`
^D
$ `ls $HOME`
```
---
# Try it: named cache volume
```
$ `docker run -it --rm -v my-cache:/cache ubuntu bash`
root@c10a43c38793:/# `echo TESTING > /cache/test`
^D
```
Observe, volume created:
```
$ `docker volume ls`
```
Use it again:
```
$ `docker run -it --rm -v my-cache:/cache ubuntu bash`
root@f5be5dec8a5a:/# `ls /cache`
```
Clean up:
```
$ `docker volume rm my-cache`
```
---
# Try it: anonymous volume for extra writable space
Tip: you can improve security by:
* mounting your root volume read-only
* creating writable volumes as required
```
$ `docker run -it --rm --read-only -v /scratch ubuntu`
root@c10a43c38793:/# `echo TESTING > /tmp/test`
root@c10a43c38793:/# `echo TESTING > /scratch/test`
```
---
# Try it: share a volume with another container
Create a container, with a volume:
```
$ `docker run -it --rm --name provider -v data:/published ubuntu`
root@118f38503653:/# `echo ohai > /published/stuff`
```
.center[
<img src="diagrams/shared-volume.png" width=80% />
]
Use the volume from a different container:
```
$ `docker run -it --rm --name consumer -v data:/provided ubuntu`
root@d88a7a468b01:/# `cat /provided/stuff`
```
---
# Creating volumes in images
Use the `VOLUME` directive in your `Dockerfile` to create a volume.
Sample from "[postgres](https://github.com/docker-library/postgres/blob/8a9fbcb40f13ccc7762f278b9df611cabe22d300/9.5/Dockerfile)" image:
```
FROM debian:jessie
RUN apt-get install -y postgresql-common postgresql-9.5
…
ENV PGDATA /var/lib/postgresql/data
VOLUME /var/lib/postgresql/data
…
```
---
name: compose
class: middle, center
# Docker Compose
---
# Try it: docker-compose
Given YAML config file:
```
version: '2'
services:
app:
image: realestate/ciao
proxy:
image: realestate/ciao-proxy
depends_on:
- app
environment:
BACKEND: app
ports:
- 5678:80
```
You can start the containers with:
```
$ `cd exercises/composed/basic`
$ `docker-compose up`
```
---
# Try it: under the covers of compose
Generate some logs:
```
$ `curl localhost:5678`
```
What containers are running?
```
$ `docker-compose ps`
$ `docker ps`
```
Take it all down:
```
$ `docker-compose down`
```
---
# Try it: get compose to build your images
```
version: '2'
services:
app:
build: ../../ciao
proxy:
build: ../../ciao-proxy
depends_on:
- app
environment:
BACKEND: app:80
ports:
- 5678:80
```
--
```
$ `cd exercises/composed/autobuilt`
$ `docker-compose up`
```
---
# Try it: sharing a volume
```
version: '2'