What's that log for?

Like any good *nix system Linux has some log files that you may find useful from time to time when trying to monitor your box or troubleshoot a problem.

Kernel boot messages
/var/log/dmesg
This is written during system boot and contains messages from the boot up process.

Standard system messages
/var/log/messages
This is the syslog file and contains messages from the system software.

Mail system messages
/var/log/maillog
This file contains messages from sendmail.

Any of these files can be viewed by root simply by issuing the cat, tail, head, etc... commands followed by the file name. Take some time to get use to these files, you'll need one or all of them one day.