After Security Update 2018-001, MacPro 1,1 no longer boot

[r2d3]

My MacPro 1,1 using Piker boot.efi worked fine until the last "Security Update 2018-001".

Now, the machine starts booting then loop back to chime ...

In verbose mode, no "interesting" (for debug) message seems to be shown.

Any idea ?

[ppinter1]

I had the same problem (see this thread) and was able to recover by restoring my last full backup.

Alternately, some people on that thread have been able to simply re-install their 'pikified' USB install image to the broken target disk to recover, preserving user data and settings.

Going forward, I logged in as 'admin' and set that Security Update 2018-001 to be 'hidden' and will be sure to check that macrumors.com thread before applying any other kernel updates in future.