http://kaukovuo.blogspot.com/2015/12/oraclevm-serial-console-not-working.html
The issue resurfaced at some point and I continued having Linux servers that printed continuous error messages like this:
Dec 18 20:33:49 lb01 init: serial_console (serial_console) main process (30384) terminated with status 1 Dec 18 20:33:49 lb01 init: serial_console (serial_console) main process ended, respawning Dec 18 20:33:59 lb01 init: serial_console (serial_console) main process (30399) terminated with status 1 Dec 18 20:33:59 lb01 init: serial_console (serial_console) main process ended, respawning Dec 18 20:34:09 lb01 init: serial_console (serial_console) main process (30411) terminated with status 1 Dec 18 20:34:09 lb01 init: serial_console (serial_console) main process ended, respawning
The fix for this modifying the /etc/udev/rules.d/50-udev.rules
Change hvc0 to ttyS0, like this:
KERNEL=="hvc0", SYMLINK+="serial_console"
to
KERNEL=="ttyS0", SYMLINK+="serial_console"
Save the file and reboot the server.