I am managing about 20 servers, many of them virtual. They are almost all different purpose, and none are clustered. I have a distributed LAMP stack, a few application servers, some build servers, a few KVM hosts. They are CentOS 6.3 mostly with a few Ubuntu (unfortunately). I don't have the resources to setup a staging environment where I can have duplicates of my machines and test updates before rolling them out. I am taking file backups. What I want to know is how you are approaching backing up your Linux systems. I assume you don't just do yum update, but then how are you choosing the packages worthy of updating? When (if ever) are you updating the kernel, etc.. How do you test updates without a staging environment? Snapshot and hope for the best?