Forum OpenACS Q&A: how to check on people accessing my server?

I would like to know who (ip-address etc.) directly accessed my
server as root (or other) in the past?

Is there a log file somewhere on my server (RH 6.2), where I could
find this information?

the unix command last should tell you who accessed your system. But be warned that educated hacker will change the access file in /var/adm