diff --git a/files/certbot-renewal.sh b/files/certbot-renewal.sh
index c2ecb69..463881e 100644
--- a/files/certbot-renewal.sh
+++ b/files/certbot-renewal.sh
@@ -3,6 +3,8 @@ dom=`date +%d`
 today=`date +%Y%m%d`
 log=/var/log/certbot-renewal.log
 echo Renewal attempt for $today >> $log
+#rotate log file every month
+if [[ $dom = 1 ]];then mv $log $log.bak;fi
 for f in `ls /etc/letsencrypt/live/ --ignore "README"`
 do
     echo Checking $f >> $log