1. Shutdown the VM.
2. Open the settings.
3. Select the hardware tab and click Add.
4. Choose Serial Port and hit next.
5. Select Output to file and click next.
6. Click Browse and choose a file location inside the VM folder on the datastore.
7. Make sure the Serial Port gets connected once the machine powers on.
8. Close the settings.
9. Power on the virtual machine.
10. At the boot prompt add the needed kernel options and hit enter.
    

Once the machine failed to boot, please check the file on the datastore if all messages from starting the kernel up to the error have been recorded and provide this file to support.

In case the file is empty, the serial port might have been connected to tty1/ttyS1 instead of tty0/ttyS0 as shown above. Please adjust the options if needed.

Starting with VMware vCenter the process of adding a serial console is slightly different:

1. Shutdown the VM.
2. Right click and select Edit Settings.
3. From the drop down menu of "New device" select Serial Port and hit Next.
4. Now just select the file location on the datastore.
5. Press OK
6. Power on the virtual machine

It may be advised to increase the BIOS timeout to the virtual machine to its maximum of 10 seconds (10000 milliseconds) to gain more time to react.

In case there is no direct input possibility for the kernel options please select the matching entry on the screen, hit 'e' to edit and add the needed options to the line containing the root volume.

console=tty0 console=ttyS0,115200 debug ignore_loglevel

systemd.log_level=debug systemd.log_target=console console=ttyS0,115200