Convert a Server to a Docker Container (Update II)

How and Why?

Let’s say you have a server that has been lovingly hand-crafted that you want to containerize.

Figuring out exactly what software is required on there and what config files need adjustment would be quite a task, but fortunately blueprint exists as a solution to that.

What I’ve done here is automate that process down to a few simple steps. Here’s how it works:

You kick off a ShutIt script (as root) that automates the bash interactions required to get a blueprint copy of your server, then this in turn kicks off another ShutIt script which creates a Docker container that provisions the container with the right stuff, then commits it. Got it? Don’t worry, it’s automated and only a few lines of bash.

There are therefore 3 main steps to getting into your container:

– Install ShutIt on the server

– Run the ‘copyserver’ ShutIt script

– Run your copyserver Docker image as a container

Step 1

Install ShutIt as root:

sudo su -
pip install shutit

The pre-requisites are python-pip, git and docker. The exact names of these in your package manager may vary slightly (eg docker-io or docker.io) depending on your distro.

You may need to make sure the docker server is running too, eg with ‘systemctl start docker’ or ‘service docker start’.

Step 2

Check out the copyserver script:

git clone https://github.com/ianmiell/shutit_copyserver.git

Step 3

Run the copy_server script:

cd shutit_copyserver/bin
./copy_server.sh

There is a prompt to ask what docker base image you want to use.

Make sure you use one as close to the original server as possible, eg ubuntu/trusty or ubuntu:14.04 rather than just ‘ubuntu’.

Step 4

Run the built image:

docker run -ti copyserver /bin/bash

You are now in a practical facsimile of your server within a docker container!

Gotchas Checklist

If it doesn’t work, here’s a checklist of things that might have gone wrong:

• Python 2.7+ is required
• Using the wrong image – make sure it’s as close to the original as possible
• Not having Docker installed on the host
• The server is not apt or yum based
• The server may run out of memory (at least 1G recommended)

If none of the above work, send the output of:

./copy_server.sh -l debug --echo
cd /tmp/shutit_copyserver && shutit build --echo -d docker -s repository tag yes -s repository_name copyserver -l DEBUG

to an issue on github.

 

My book on Docker:

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