Canteens across the country were to show the daily menu on screens, driven by small Raspberry Pi boards that staff routinely switched off straight at the wall socket.
Problem
Hard power-offs corrupted the file system on the SD card. After a while the devices stopped booting, and fixing them meant a trip on site – to dozens of locations all over the Czech Republic.
Goal
The device must survive any power-off, and the whole deployment must be fully automatic: plug it in, switch it on and deal with nothing else on site.
Solution
- Read-only file system: the system mounts read-only at boot, so pulling the plug has nothing to corrupt.
- Modified Raspbian that boots and runs with a read-only system – including the parts that normally write to disk.
- Automatic deployment without a technician at the location.
Outcome
The devices coped with everyday canteen operation, including being unplugged, and were deployed without site visits.