In case of power failure, does the Pi desktop turn off the raspberry Pi safely?

Question

In case of power failure on the network, does the Pi desktop turn off the raspberry Pi safely?

shabaz · Accepted Answer

Hi, I think that requires a UPS, the desktop Pi behaves like any desktop PC as I understand (I could be wrong).

rew · Answer

Once the power goes, the raspberry pi has no way of "shutting down nicely": the power is gone.

An UPS can help in such a case. IIRC, you can buy them commercially.

I am currently working on a project where I powered a raspberry pi (compute module) from a lab power-supply. I Had set the current limit to 1.05A (5.4W), and my power supply at one point in the boot process decided: That's more than 1.05A, you can go... well, the power dip is less than 100ms, but the pi crashed and then starts to boot again and in the end it keeps crashing at exactly the same point every time.... (all this while the average current is now under 600mA).

beacon_dave · Answer

I recall an earlier discussion about this on here and that some members were using USB power banks as UPS devices for their R-Pi projects. https://www.element14.com/community/message/212180/l/re-build-idea-raspberry-pi-upsuninterruptible-power-supply#212180 There also appears to be a 'Live CD/USB' type SDK for the R-Pi Nard SDK which may at least help avoid the OS on a SD card from becoming corrupted due to an unexpected loss of power.

gdstew · Answer

No, you are absolutely right. Without a power backup of some kind there is a very good chance that data on the SD card will get lost or corrupted if a file operation is in progress. Using a journal file system like ext4 will help, but it can not prevent data loss in all cases.

baldengineer · Answer

I Had set the current limit to 1.05A (5.4W), and my power supply at one point in the boot process decided: That's more than 1.05A, you can go... (all this while the average current is now under 600mA).

About a year ago I measured the current draw of a Pi 3 using a current probe on my scope. In this attached shot, you can see there are >1 Amp transients. This measurement was like a PS1 emulator was running Final Fantasy 8. I thought I had one from the boot process, but I cannot find it at the moment.