Docker Workshop

Evans Ye2014.10.13

Agenda• Docker and underlying technologies• Running Docker containers• Building Docker images• The official Docker hub

Containers offer faster automation

HOW?

Docker Container• A container is a group of isolated processes

– cgroups– namespace

• Isolated processes run straight on the host– native CPU performance– minimal memory overhead– minimal network performance overhead

7

CGroups

Cgroups (control groups)• Linux kernel feature• Groups of processes• Resource limitations

– Like limits.confbut the scope is a set of processes instead of uid/gid

• May be nested

Cgroups submodules• memory• CPU• network IO• disk IO

10

Namespaces

namespaces• Linux kernel feature• wrap particular global system resource in an

abstracted, isolated instance• May be nested

Different kinds of namespaces

#TrendInsight

Running Docker Containers

Run Docker container in boot2docker directly

Create a container with interactive shell$ docker run -t -i base:centos62 /bin/bash

[root@4d8c4b81f6d7 /]# exit (exited)

$ -t, --ttyAllocate a pseudo-TTY

$ -i, --interactiveKeep STDIN open even if not attached

Check containers’ status$ docker ps

(only running containers are shown)$ docker ps –a

(all)

Reattach in stopped container$ docker start -i 4d8c4b81f6d7[root@4d8c4b81f6d7 /]#

Take a look at Docker run command$ docker run -t -i base:centos62 /bin/bash

Command + args$ docker run base:centos62 /bin/cat /etc/hosts

Name a container$ docker run -ti --name foo base:centos62 /bin/bash$ docker ps -a

$ docker rm foodestroy foo container

Destroy all containers$ docker rm `docker ps --no-trunc -aq`

(except running containers, they must be stopped first)

$ docker rm -f `docker ps --no-trunc -aq`(force destroy all containers)

Create ephemeral container$ docker run -ti --rm base:centos62 /bin/bash

[root@4d8c4b81f6d7 /]# exit (destroyed upon exit)

$ docker ps -a

Ports forwarding (publish)$ docker run -ti -p 80:80 base:centos62 /bin/bash# yum install httpd# echo "hello world" > /var/www/html/index.html# service httpd start$ curl localhost:80

What does Docker port forwarding do?

Windows / OS X

boot2docker

Container Container 80

80

26

Well, I need to render it

in browsers…

How about this?

Windows / OS X

boot2docker

Container Container 80

80

80

Doable via Vagrant$ vim Vagrantfile

The solution

Windows / OS X

boot2docker

Container Container 80

80

80

Docker port forwarding Vagrant port forwarding

More about Docker ports forwarding$ docker run -ti -p 80:80 base:centos62 /bin/bash

• -p, --publishPublish a container's port to the host

• format: – ip:hostPort:containerPort (10.1.1.1:80:80)– ip::containerPort (10.1.1.1::80)– hostPort:containerPort (80:80)

Volume (like sync folder)$ docker run -ti --name apache

-v /httpd-logs:/var/log/httpd base:centos62 /bin/bash

# touch /var/log/httpd/foo

$ ls /http-logs

Volume from other container (useful to share data)$ docker run -ti --volumes-from apache

base:centos62 /bin/bash

# ls /var/log/httpd

Link$ docker run -ti --link apache:apache.spn.tw.trendnet.org

base:centos62 /bin/bash# cat /etc/hosts

• Exposes information from source container to recipient container in two ways:– Environment variables– Updating the /etc/hosts file

• format:– name:alias

04/09/2023

useful in multi-node situation

service(hadoop-client)

data(hadoop-client)

link

Docker in client/server mode

Windows / OS X

boot2docker(Docker client)

Linux server

Docker Engine

Container Container

Server: bind Docker engine to a tcp port$ docker -d -H 10.1.1.1:2375 -H

unix:///var/run/docker.sock

• -d, --daemondaemon mode

• -H, --hostthe socket(s) to bind in daemon mode

Docker client$ export DOCKER_HOST=tcp://10.1.1.1:2375

$ docker images

$ docker run -ti --rm centos:centos6 /bin/bash(start container on the server)

• Note: – expose tcp port could let someone get root access to the host – not recommended in open network

Running containers in background (Detached mode)

$ hadoop=$(docker run -d -p 50070:50070 tmh6:centos62)

$ docker inspect $hadoop

39

Vagrant creates Docker containers in

detached mode

Some other VM-like operations$ docker stop $hadoop$ docker start $hadoop$ docker kill $hadoop$ docker rm $hadoop

https://docs.docker.com/reference/commandline/cli/

#TrendInsight

Building Docker Images

42

There are two ways to build docker

images

First: commit an existing container• Do changes manually, then commit

quick and dirty suitable for experiment might be deleted in the future

Second: Build from Dockerfile• Dockerfile is a series of instructions• Use "Docker build" command to build images• pros:

– build images automatically by following instructions– visible and easy to understand instructions– enable Docker specific functions in the image– repeatability

A sample httpd service DockerfileFROM base:centos62COPY index.html /var/www/html/index.htmlRUN yum -y install httpdEXPOSE 80CMD ["/usr/sbin/httpd", "-D", "FOREGROUND"]

Build$ mkdir apache-server$ cd apache-server$ echo "our first docker image" > index.html$ vi Dockerfile (paste the sample and save it)$ docker build -t apache:0.1 ./

Build context• docker build -t apache:0.1 ./• ./ will be transferred to Docker daemon as build

context• Must have a Dockerfile there

– ./Dockerfile

• DO NOT build at /– docker build -t apache:0.1 /

Run the apache image$ docker run -d --name apache apache:0.1

$ docker run -ti --rm --link apache:a01 base:centos62 /bin/bash

# curl $A01_PORT_80_TCP_ADDR(you see how link and expose work together)

49

Use entrypoint to bind a specific

executable to the image

An httpd service exampleFROM base:centos62COPY index.html /var/www/html/index.htmlRUN yum -y install httpdEXPOSE 80ENTRYPOINT ["/usr/sbin/httpd"]CMD ["-D", "FOREGROUND"]

The difference$ docker run -ti --rm apache:0.1 /bin/bash# (get into the container)

$ docker run -ti --rm apache:0.2 /bin/bashshow httpd helper message

the only thing you can do is to pass args to httpd

Make sure init script always being executedFROM base:centos62…ENTRYPOINT ["init_wrapper_script"]CMD ["default_args"]

https://docs.docker.com/articles/dockerfile_best-practices/

SHIPPING CONTAINERS

Tagging an image$ docker tag -h

• dockerhub.evansye.com/base:centos62– REGISTRYHOST = dockerhub.evansye.com– NAME = base– TAG = centos62

#TrendInsight

The official Docker hub

Redis$ docker run -d --name some-redis redis$ docker run -ti --rm --link some-redis:redis redis

/bin/bash# redis-cli -h $REDIS_PORT_6379_TCP_ADDR -p $REDIS_PORT_6379_TCP_PORT

https://registry.hub.docker.com/_/redis/

MySQL$ docker run -d --name some-mysql -e

MYSQL_ROOT_PASSWORD=demo mysql

$ docker run -it --link some-mysql:mysql --rm mysql sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"'

https://registry.hub.docker.com/_/mysql/

Jenkins$ docker run -d -p 8080:8080 Jenkins

http://HOST_IP:8080

https://registry.hub.docker.com/_/jenkins/

Private Docker registry$ docker run -d -p 5000:5000 registry

$ docker tag IMAGE HOST_IP:5000/NAME:TAG

$ docker push HOST_IP:5000/NAME:TAG

https://registry.hub.docker.com/_/registry/

#TrendInsight

Summary

Recap docker run• we’ve learned:

– port forwarding– volume mounting– linking containers together– running containers at remote

Recap docker build• we’ve learned:

– how to write a Dockerfile– how expose and link work together– use entrypoint to bind a specific executable with image– ship images to the registry

#TrendInsight

Q & A

Re-associate Vagrant with VM• VBoxManage list vms

• cd .vagrant/machines/docker-platform/virtualbox/

• touch id• echo 33ca… > id