Sorry to ask a (probably) stupid question. I am a hardware designer struggling with provision of safe shutdown power to an embedded system. I am aware the Linux normally makes a heavy use of the filesytem and makes metadata updates whenever a file is read -i.e. there is a consequential write for every file access. I believe it is possible to delay this write. I am wondering what happens if this is an indefinate delay (i.e. it never occurs). Some background:
For operational reasons it is preferable not to use battery backup to provide power during system shutdown- which means I am looking at a 1 to 5 second power down hold-up. This doesn't seem long enough for the O/S to shut down form our S/W engineers' testing. We are all "new" to Linux having been using conventional embedded RTOS up to this point.
We will boot from a FLASH drive and run in RAM in the machine so if we have zero FLASH writes then it wouldn't normally be corrupted on a power fail.
We will store system NV data in FLASH that is controlled by a small micro that guarentees a write success in 10ms so that's fine - however I am struggling to understand what, if anything, Linux has to write back to the drive it booted from - and if we prevent it doing so what consequence would there be?
Unfortunately we're running from a uSDHC card at the moment so I can't simply write protect it in hardware to find out :-(
Can anyone help me or point me at where to learn this information.