In information technology, log rotation is an automated process used in system administration in which dated log files are archived. Servers which run large applications, such as LAMP stacks, often log every request: in the face of bulky logs, log rotation provides a way to limit the total size of the logs retained while still allowing analysis of recent events.
Methods of archival
In Linux log rotation is typically performed using the logrotate command. The command can be used to email logs to a systems administrator after log rotation. Dated logs may also be compressed.
In FreeBSD and OS X newsyslog command is used. It has the ability to trigger rotation based on file size, time or interval (or any combination thereof). It can compress the archives and send a signal to a process to reset logging.
The command is often run as a cron job, which has the effect of fully automatic log rotation.
Typically, a new logfile is created periodically, and the old logfile is renamed by appending a "1" to the name. Each time a new log file is started, the numbers in the file names of old logfiles are increased by one, so the files "rotate" through the numbers (thus the name "log rotation"). Old logfiles whose number exceeds a threshold can then be deleted or archived off-line to save space.