Nginx Server Crash Or VIrtualmin Crash
Best way to find out what's going on is by checking your server logs. They are in following directory.
there are lots of logs, which log to check for the server crash, below two lines are from syslog, are they causing the crash or have to check all the logs
Nov 26 23:28:25 www named: network unreachable resolving 'no-reverse-dns-configured.com/DS/IN': 2001:503:d414::30#53
Nov 26 23:28:25 www named: network unreachable resolving 'no-reverse-dns-configured.com/DS/IN': 2001:502:1ca1::30#53
Go through syslog and look for errors. Low memory is a common cause for crashes. Look for memory related lines. Also look at the Virtualmin logs directory for clues.
syslog, found but clamscan is disabled from server>bootup & shutdown section webmin
Nov 27 12:20:54 www kernel: [1241277.478711] Out of memory: Kill process 32211 (clamscan) score 355 or sacrifice child
Nov 27 12:20:54 www kernel: [1241277.484350] Killed process 32211 (clamscan) total-vm:605896kB, anon-rss:454048kB, file-rss:1548kB
clamscan us used by maldet for real-time protection. How much RAM does your server has?