There are a lot of pre-built images available on Docker Hub — most recent OS builds, Apache, MariaDB, there’s even an Oracle Enterprise database server. If you’ve got a fairly recent OS, you can start from that base image and use Dockerfile (or in a CI/CD pipeline, the before_script) to install additional components. But if your OS is out-of-date … you still need a test platform that matches production! You can create your own Docker image without using a base.

First, you need a server. This can be your current dev box (or your current prod box, but I avoid touching the prod boxes!). It can be a new install. Either way, you need a server. Log in and su to root. Then tar off the installation:

tar -czf /image/centos51.tgz ./ --exclude /image

Once you’ve got a tar of the server, scp the tar to whatever computer is running your docker client. Import the image to Docker. (You can tag the image and upload it to a registry, if you’ve got one.)

docker load centos51.tgz sampleproject/cent51

Finally, start a container based on the image:

docker run -p 80:80 -p 443:443 -v /data/docker/certs:/etc/httpd/certs -v /data/docker/conf.d/SampleProjectSite.conf:/etc/httpd/conf.d/SampleProjectSite.conf -v /data/git/SampleProjectCode:/var/www/vhtml/SampleProject/html -dit --name SampleProject sampleproject/cent51 /bin/bash