Apache stops for unknown reasons, how to track down the "killer"?

Question

linux

Hello, please tell me which way to dig. There is a server on Ubuntu Server 16.04. There are many different services running on the server, everything works like clockwork. But since recently apache has stopped for reasons unknown to me. I looked at the Apache logs, the last line says that he caught SIGTERM. Those. As far as I understand something stops him. Tell me where can I see who stops him? If you need any logs or additional information, I will be happy to share. This happens about twice a day.
PS ISPConfig is installed on the server. Maybe it's in him?

Answer 1

1 Apache log writing mode - debug
2 Application log writing mode (if any) - debug
3 Apache log
analysis 4 Application log analysis (if any)
5 Analysis of other logs (maillog, messages, secure, auditd, whichever you have there base)
6 System boot analysis (htop, iotop, ...)