#server-id = 1
log-bin = /var/log/mysql/mysql-bin.log
#if you set the expire_logs_days = x var in the [mysqld] section of your my.cnf it will automatically rotate your bin logs after x days.
expire_logs_days = 30
#it will create a new log file when the current file reach the specified size.
max_binlog_size = 100M