Tuesday, December 8, 2015

How to use Docker

Docker
Docker offical webiste: https://www.docker.com/
Setup Docker
Prepare fresh version of CentOS, I am using CentOS 6.7.
Update the yum rep.
> rpm -iUvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
> yum update -y
 
Install Docker
> yum -y install docker-io

Pull some image of container, I am going to use CentOS container.
To pull the latest (CentOs 7)
>  docker pull centos
Or
> docker pull centos:centos6

Check which container images are installed:
> docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
centos              centos6             3bbbf0aca359        2 weeks ago         190.6 MB
centos              latest              ce20c473cd8a        2 weeks ago

Run docker from image:
> docker run -i -t centos:centos6 /bin/bash
Note: this creates a container from image (you can see the ContainerID as hostname)

List containers:
>docker ps
>docker ps -a (To List all Containers running/stopped)

Stop/Start/Remove container:
>docker start ContainerID
>docker stop ContainerID
>docker rm ContainerID
 
Re-connect to Container
>docker attach ContainerID
Or
>docker exe -it ContainerID bash

Run docker container In Background:
> docker run -itd --name cs1 --net=none --hostname=cs1.csteam.net -v /csdata/cs1:/csdata/cs1:rw -v /root/.ssh:/root/.ssh:rw --privileged=true centos:centos6 /bin/bash
To exit Docker console:
Ctrl+P => Ctrl+Q

Networking

For following steps, you need to install pipework script.
#sudo bash -c "curl https://raw.githubusercontent.com/jpetazzo/pipework/master/pipework > /usr/local/bin/pipework"
#sudo chmod +x /usr/local/bin/pipework

If you want to set IP address for container with DHCP. Then you don't need the next section. Setting DHCP settings is easier:
#pipework eth0 ContainerID dhclient
How to expose container with Private IP address from local network: MacVLan method
Host type is easy to setup(-net=host) but the container uses the same network interfaces and can not have their own IP address. That is why, we will use bridged network.
Easier way to setup bridged network is to use "pipework" script that automatizes the procedure.
Install pipework.
>sudo bash -c "curl https://raw.githubusercontent.com/jpetazzo/pipework/master/pipework > /usr/local/bin/pipework"
>sudo chmod +x /usr/local/bin/pipework

Install dependencies:
>yum -y install bridge-utils net-tools
Note:
If your host server is CentOS 6, then you need to upgrade iproute rpm to support "ip netns" command.
Download RPM from:
https://repos.fedorapeople.org/repos/openstack/EOL/openstack-havana/epel-6/iproute-2.6.32-130.el6ost.netns.2.x86_64.rpm
(or iproute-2.6.32-130.el6ost.netns.2.x86_64.rpm)
>rpm -Uvh iproute-2.6.32-130.el6ost.netns.2.x86_64.rpm

Creating bridge(suppose that your Host's Ip=10.40.198.150 on eth0):
>ip addr del 10.40.198.150/24 dev eth0
>ip link add link eth0 dev eth0m type macvlan mode bridge
>ip link set eth0m up
>ip addr add 10.40.198.150/24 dev eth0m
>route add default gw 10.40.198.1
>service network restart
You need to wait for few minutes till the settings get applied.
And, Finally assign $CID container the new private(local) IP :
>pipework eth0 $CID 10.40.198.155/24@10.40.198.1
Done!
you can ping from other local PC, ping 10.40.198.155

How to remove unused virtual network:
>ifconfig br0 down
>brctl delbr br0

Saving Container as Image:
>docker commit $CID myimage:newcs