In a Debian standard installation of MySql 4, binary logs are purged automatically. The file /etc/mysql/debian-log-rotate.conf is needed to tell logrotate how many log files to keep.
Starting from MySql 5, purging of binary logs is done directly by MySql so there is no more need of debian-log-rotate.conf and the rotation is configured in the my.cnf file with the following entry:
expire_logs_days = 30 # WARNING: Using expire_logs_days without bin_log crashes the server! See README.Debian!