How to make docker image of host operating system which is running docker itself?

Question

I started using Docker and I can say, it is a great concept. Everything is going fine so far. I installed docker on ubuntu (my host operating system) , played with images f

Answer 1

I'm not sure to understand why you would want to do such a thing, but that is not the point of your question, so here's how to create a new Docker image from nothing:

If you can come up with a tar file of your current operating system, then you can create a new docker image of it with the docker import command.

cat my_host_filesystem.tar | docker import - myhost

where myhost is the docker image name you want and my_host_filesystem.tar the archive file of your OS file system.

Also take a look at Docker, start image from scratch from superuser and this answer from stackoverflow.

If you want to learn more about this, searching for docker "from scratch" is a good starting point.

Answer 2

I was doing maintenance on a server, the ones we pray not to crash, and I came across a situation where I had to replace sendmail with postfix.

I could not stop the server nor use the docker hub available image because I need to be clear sure I will not have problems. That's why I wanted to make an image of the server.

I got to this thread and from it found ways to reproduce the procedure.

Below is the description of it.

We start by building a tar file of the entire filesystem of the machine (excluding some non necessary and hardware dependent directory - Ok, it may not be as perfect as I intent, but it seams to be fine to me. You'll need to try whatever works for you) we want to clone (as pointed by @Thomasleveil in this thread).

$ sudo su -
# cd /
#  tar -cpzf backup.tar.gz --exclude=/backup.tar.gz --exclude=/proc --exclude=/tmp --exclude=/mnt --exclude=/dev --exclude=/sys /

Then just download the file into your machine, import targz as an image into the docker and initialize the container. Note that in the example I put the date-month-day of image generation as image tag when importing the file.

$ scp user@server-uri:path_to_file/backup.tar.gz .
$ cat backup.tar.gz | docker import - imageName:20190825
$ docker run -t -i imageName:20190825 /bin/bash

IMPORTANT: This procedure generates a completely identical image, so it is of great importance if you will use the generated image to distribute between developers, testers and whateever that you remove from it or change any reference containing restricted passwords, keys or users to avoid security breaches.