After installing Plesk update (with base component update) on Debian 6 or 7,
xinetd process is stopped.
On the final stage of update the following entries can be found in log files::
root@a1-2-3-4:~# tail /var/log/syslog /var/log/dmesg | grep xinet
Sep 23 19:25:51 a10-52-142-18 xinetd: Exiting...
The issue has been reported to Maintenance Team as internal issue with ID #PPPM-2503 . This software issue has been fixed Plesk 12.0.18 MU#50 according to Plesk 12.0.18 Release Notes
Install all the latest Plesk 12.0.18 updates.