Slides for an introductory presentation on Docker

1. An Introduction to Docker
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Ruben Taelman - @rubensworks
imec - Ghent University

2. So what is Docker?
Platform for running software in isolated containers
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3. So what is Docker?
Platform for running software in isolated containers
3
Traditional webserver
NGINX
PostgreSQL
Node

4. So what is Docker?
Platform for running software in isolated containers
4
Traditional webserver Docker webserver
NGINX
PostgreSQL
Node
NGINX
PostgreSQL
Node

5. So what is Docker?
Platform for running software in isolated containers
5
Traditional webserver Docker webserver
NGINX
PostgreSQL
Node
NGINX
PostgreSQL
Node
✓Linux ✓Windows ✓Mac

6. (Reproducible) software evaluations
Easily installable and disposable software
Running different software versions simultaneously
What to use Docker for?
6

7. Overview
Basics
Networks
Convenience tools
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8. Overview
Basics
Networks
Convenience tools
8

9. Virtual machines vs containers
(Docker) containers don’t need separate OS’s, so they are more lightweight.
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10. Docker workflow
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Dockerfile Image Container
Build Run
Description of an image Built image
Available for reuse
Instantiated image

11. Dockerfile
Layered image descriptions
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Debian
Node JS
LDF server

12. 12
# Inherit from the Node 4.2.2 image
FROM node:4.2.2
# Copy the server files
ADD . /app
# Install the node module
RUN cd /app && npm install
# Expose the default port
EXPOSE 3000
# Run base binary
ENTRYPOINT ["node", "bin/ldf-server"]
# Default command
CMD ["--help"]
> cat Dockerfile

13. RUN Executed when the image is being built
Zero or more RUN’s per Dockerfile
Typically used for installing software
Result will be stored in image
CMD Executed when the image is being run/instantiated
Only one CMD per Dockerfile
Default command to run when starting the container
Can be overridden by user
! Difference between RUN and CMD !
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14. Build image to your local repository
Building a Dockerfile to an image
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> docker build -t <image-name> <path-to-dir>

15. All your available images
Your local image repository
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> docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ldf-server latest db3a7fb38cb2 10 minutes ago 683.3 MB
stuff latest do89d002jbsd 1 week ago 102.2 MB

16. http://hub.docker.com
Reuse existing images
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17. Search the Docker hub, and download images to your local repo
Or use the command-line...
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> docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
ubuntu Ubuntu is a Debian-based Linux operating s... 4958 [OK]
ubuntu-upstart Upstart is an event-based replacement for ... 67 [OK]
rastasheep/ubuntu-sshd Dockerized SSH service, built on top of of... 47 [OK]
> docker pull ubuntu
12.04: Pulling from library/ubuntu
ba2b457ecfb2: Pull complete
26180b0fe8fb: Pull complete
edd7c1974a70: Pull complete
57bca5139a13: Pull complete
library/ubuntu:12.04: The image you are pulling has been verified.
Status: Downloaded newer image for ubuntu:12.04

18. Instantiate an image
Running an image
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> docker run -it --rm ldf-server
Important options:
-i
-t
--rm
-d
-p 8080:80
-v /mydir:/targetdir
...
Keep STDIN open
Allocate new terminal
Remove container after stopping (default: stopped state)
Run in background
Map host port to container port
Map local directory to container directory

19. List running containers
List running + stopped containers
Stop container
Remove container
List images
Remove image
Image and container management
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docker ps
docker ps -a
docker stop <container-hash-or-name>
docker rm <container-hash-or-name>
docker images
docker rmi <image-name>

20. Attach an image (not guaranteed to have a CLI)
Using detached containers
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> docker attach <container-hash>
Open shell in container (useful for debugging)
> docker exec -it <container-hash> /bin/bash
CTRL+p CTRL+q to detach

21. Overview
Basics
Networks
Convenience tools
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22. Connect microservices
using virtual Docker networks
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Docker webserver
NGINX
PostgreSQL
Node

23. Managing networks
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> docker network ls
NETWORK ID NAME DRIVER
7fca4eb8c647 bridge bridge
9f904ee27bf5 none null
cf03ee007fb4 host host
Default
Dummy network
Same as host network
> docker network create --driver bridge <network-name>
> docker network inspect <network-name>
> docker run --network=<network-name> <image-name>

24. using Docker swarm
Swarm
Running containers on multiple hosts
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Manager
Node 1Node 0 Node 2

25. Scale applications, by running containers N times
Load balancing
Automatic management
Deploying applications in clusters
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26. Scale applications, by running containers N times
Load balancing
Automatic management
Deploying applications in clusters
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27. Overview
Basics
Networks
Convenience tools
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28. Docker Compose
Declaratively define multi-container applications in docker-compose.yml
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> docker-compose up -d
> docker-compose stop
> docker-compose rm

29. 29
version: '2'
services:
server:
image: linkeddatafragments/server.js
ports:
- "3000:3000"
volumes:
- ${DATA_DIR}:/data
- ./config-server.json:/tmp/config.json
command: /tmp/config.json 3000 ${LDF_WORKERS}
server-cache:
image: nginx:stable
ports:
- "80:80"
volumes:
- ./nginx-default:/etc/.../default:ro
links:
- server
> cat docker-compose.yml

30. Docker Machine
Install Docker Engine on any host
Easily SSH to any host to control it
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31. Methods for measuring CPU, memory usage, I/O …
Third-party alternatives: Datadog, CAdvisor, Scout ...
Monitoring
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> docker stats
CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O
1285939c1fd3 0.07% 796 KiB / 64 MiB 1.21% 788 B / 648 B 3.568 MB / 512 KB
9c76f7834ae2 0.07% 2.746 MiB / 64 MiB 4.29% 1.266 KB / 648 B 12.4 MB / 0 B
d1ea048f04e4 0.03% 4.583 MiB / 64 MiB 6.30% 2.854 KB / 648 B 27.7 MB / 0 B

32. Overview
Basics
Networks
Convenience tools
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