Command to remove files older than N days

The below command removes files older than 2 days in the current directory

sudo find .  -mtime +2 -exec rm {} \;

Monitoring open connections in MySQL

Use the following commands

show status like '%onn%';

show processlist

Renew SSL certificates - courier and imap server in Ubuntu

Remove the expired .pem file

rm  /etc/courier/imapd.pem

Just open and check if the entries are recent (like contact email etc). This is NOT a mandatory step.

nano  /etc/courier/imapd.cnf

 Issue the following command to create new .pem file

mkimapdcert

Restart imap SSL service

/etc/init.d/courier-imap-ssl  restart