[beagleboard] Any issues with sudden unexpected power down?

This is the case for all SD card, even those on a PC. If you are writing to it and power down it can be rendered unusable. But, it is easy to fix by trying it again and not touching the power switch.

The bone only has the SD connector and does not have an internal one. And yes, it can have this issue as well. Processors cannot function without the power and neither can SD cards. If it dies in the middle of a write, then all bets are off. That is where having battery power can help to prevent these sort of things.

Gerald

The filesystem is on the SD card for the information you want to save. You can use a filesystem in the SDRAM, but that will go away on power down. I have yet to see a read only SD card. I suppose if you never wrote to it it would be a read only.

Bottom line. As long as you never write, no real chance for any corruption, That suggest a static system that never changes and collects no data to be saved…

Gerald

You can run a system in read only mode having all temporary data in ram, but you will have modify existing scripts for this

microSD does not have a physical lock switch.

Even on full size SD cards, the lock switch is a host side indicator
saying to not write to the card, the card itself does not enforce the
lock switch desires. Many (most? all?) embedded boards that have full
size SD card slots don't even connect the lock switch detection pins.

You can make an SD card read only by simply mounting all of its
partitions read-only (ro in fstab). Linux then should not write to
it. You can mount your USB drive as read-write (rw). But be aware,
any block device that's not battery backed in some way may have issues
when power goes away during writes. A journaled file system will help
quite a lot, but won't save you in all cases, especially ones where the
block device doesn't act as Linux expects (flash memory based devices
sometimes do this). Use of a spinning media hard disk or a battery
backing is strongly advised if you really care about performance during
unexpected power loss.

-Andrew