How do I run a thorough low-level hardware memory test to discover any bad memory cells that may exist?
If I do find bad memory cells, do I need to replace the RAM or can I flag the specific cell addresses as bad so OPNsense will not use them?
1. Download this: https://memtest.org
2. Create a bootable USB drive according to the instructions.
3. Boot from that USB drive.
I know this isn't an option for everyone, but if you suspect some RAM, then it might be worth just replacing it. I've never had much luck with memtest finding issues, but replacing has normally cured the problems.
Thanks @PatrickMHausen and @Greg_E.
I'll try memtest, followed by 'memswap'.
One thing to keep in mind... Many years ago I had some workstations from a big name company, these had garbage processor sockets. We had recurring issues with pin in the CPU socket getting bent and most often these manifested in memory errors. Sometimes the vibration from pulling the ram modules and reseating them would put things back to working. After I figured out it was most likely a processor socket issue, I just pulled the processor and got a magnifier out and looked for bent or corroded pins.
Shortly after (like 2 years) we upgraded those to HP Z series workstations.