From AdminWiki

This should give you a rundown on the absolute minimum every server should have.

Time issues

There is absolutely no excuse for not having a correctly synchronized clock. The problem gets even worse when you are administrating multiple servers which interact with each other and you've to compare logfiles from those machines.

The problem got worse in the last years (at least that's my impression) because processors got faster and time-keeping-mechanisms sloppier. What the operating system basically does ^[1]

when booting up is fetching the current time and date from the realtime clock, then taking a wild guess how many CPU cycles (or any other time source, e.g. HPET) are approximately one second and then using this value as long as the OS runs. Excessive IRQ usage, cpu cycle modulation (power saving) and other factors might also aid the inaccuracy.

• backup
• monitoring
• sane logging
• handling of (security) updates