A couple of weeks ago I installed Ubuntu 16.04 on a HP Z420 workstation. The BIOS is labelled J61 v01.02. Yesterday Ubuntu stopped starting properly, displaying this error message:
a TPM error (7) occurred attempting to read a pcr value
After that I can either fall back to a root shell or reboot. I made some research on TPM, which is a security feature available in Intel processors. I therefore tweaked the system security settings available in the BIOS, as the image below shows:
I enabled in succession "Embedded Security Device" and "Reset of Embedded Security Device through OS". Still, after these changes Ubuntu is unable to start.
I just tried booting with a USB drive and it all went fine. I also took the time to check all the hard drives and no errors were reported. Therefore at this stage I doubt this is related to BIOS settings. What could be the cause? Is there something to be done about it?
Update: Badly needing this system, I took a more radical approach: reset the BIOS to factory and reinstalled Ubuntu. The latter did it somehow, Ubuntu is now able to start up correctly, even though briefly displaying the TPM error message on occasion.
Note that I will no longer be able to test suggestions related to the OS itself. If you have other remarks please leave a comment.