Log File Maintenance
You can capture logs. Fantastic! Now just let the log files grow until they fill your hard disk and leave room for nothing else, right? Or you can discard old logs and have the system keep the logs to a manageable size. This is called log rotation.
Look at the system messages log, /var/log/messages, and you should see six messages files: messages, messages.0.gz, messages.1.gz, messages.2.gz, messages.3.gz, and messages.4.gz. The plain messages file is the current log file. The other files are older logs; messages.0.gz is the newest, and messages.4.gz is the oldest.
When the current log file hits either a certain age or a specific size, log rotation discards the oldest log file (messages.4.gz), and the second-oldest file, ...