Ask HN: What type of sever configuration management software should I use?

I have two system running my production (Linux) and now adding one more. I manually copy over Nginx, sshd, Mysql etc. configuration files. Figured now is the time to move to something like ansible, fabric etc.

A friend suggested docker, but the problem is, I can change my existing production machines’ infrastructure. The downtime is way too much to accept.

Do you have suggestions?