OReilly Network has posted a list of the top seven things system administrators forget to do. The list varies from forgetting to delete former users accounts to not searching for rootkits on a regular basis.
I could cite many reasons why they forget some critical tasks. Those reasons include doing jobs that normally take two or more people, having to provide break-fix services on hardware, covering for absentee help desk personnel or getting involved in pre-sale activities. Regardless, here is the compilation of the top seven things system administrators forget to do.