View the original community article here
Last tested: Mar 13, 2020
By default, for Looker-hosted instances, Looker keeps one running log, at
looker/log/looker.log. Every day, it cuts off that log and saves it as a new file with the date in the filename. Then after a week, a script zips up those logs.
If you host your own instance, then there is an option in the Admin panel to change the frequency of this log rotation.