There are the OSCAR docker files that are designer to init an oscar-packager build environment ready to use.

HOWTO use it:
Chose wich distro you want to play with and then:

0/ Install docker on your linux host.
yum -y install docker
dnf -y install docker
urpmi --auto docker
apt-get -y install docker
or what ever is suitable for your distro.

1/ Build the docker image:
sudo docker build -t <yourname>/oscar_<distro>:<version> -f Dockerfile.<distro> .
example:
sudo docker build -t john/oscar_co7:1.0 -f Dockerfile.centos7 .

2/ Run the docker image you've built:
sudo docker run -it <yourname>/oscar_<distro>:<version>
example:
sudo docker run -it john/oscar_co7:1.0

3/ Now that you're running your image, strat playing with oscar-packager.
oscar-packager --all oda

=> Result will end into /tftpboot/oscar/<oscar-distro-tag>/

To build all packages:
oscar-packager --all unstable
you can add --verbose or even --debug for more output.

Now you can stop/quit your docker image by exitting the bash (exit / ^D)

4/ Once done playing, you can choose to keep your track of the state of the docker image you've just quit.
To do so:
sudo docker ps -a
Note the container id that you want to keep track (the most recent)
sudo docker commit <contained_id> john/oscar_co7:1.1

Note that the version has increased. This is to avoid overriding the 1.0 version. Though, you could have used 1.0 to store the current image status if you don't mind keeping the 1.0 version.

More infos on how to use docker here:
https://training.docker.com/self-paced-training