I recently had an ubuntu server slow to its knees, and when trying to figure out why I realized it didn't have
iostat installed. The system was stressed out to the point where I couldn't install the package, making me realize that I need to pre-install whatever diagnostic tools I think I might need.
So I turn to you, dear wise community. What diagnostic tools should I ensure are installed on my Ubuntu Precise server before it goes awry, in case I need them?