Power loss behaviour - is there some basic action?

[Sam Varshavchik]

Bo Berglund writes:

> I am wondering about what is expected to happen in the case of a power loss  
> on
> an Ubuntu 24.04.1 server running on ASUS NUC-13 hardware.

Everything comes to a screeching halt.

> Specifically I would like to know if there is something built into the BIOS  
> or
> Linux kernel that watches for this and uses the last moments of power to  
> protect
> against damage to files and such.

Nope. But current filesystems like ext4 and btrfs are designed so that they  
can (hopefully) survive such an event and during a reboot they'll recover at  
least to the point of being usable.

> In my thinking there could be a detection of loss of incoming power, which  
> could
> trigger some safeguard actions using the last tens of milliseconds of power.
> But is there such a thing?

Nope.

> Even with a battery backed poower supply (UPS) power will eventually run out  
> on
> a long power outage...

But hopefully the UPS will be one of the ones that are supported by apcupsd  
or nut, and an orderly shutdown takes place long before that happens.

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