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FS Corruption due to dropping power
Added by Keith Fletcher about 12 years ago
Hi, We are developing a system where the user is unlikely to power down gracefully, even if asked to do so and ultimately intend to use a read only file system. However in testing we have not done this and have been dropping power to switch off, and relying on the jffs file system, and the fact that we don't create or manage any files to run the system, hence any file changes will be linux managed system files.
We are using CL Mity 1808 cards with the default CL linux kernel, and a couple have developed identical faults:
1) serial port generates output, but will not respond to input data once the Linux kernel is running (Although I can break in at the uboot stage and all is fine)
2) I can no longer use ssh to talk to the card. (although I can ping the card, and control my auto booting application through the ethernet).
When the first card showed these symptoms I put it down to corruption of files due to dropping power to switch off. But for a second card to show exactly the same symptoms I am now concerned there may be something more systematic here.
Does any body know if these symptoms are typical of file corruption caused by powring off ?
Thanks for any help
Replies (2)
RE: FS Corruption due to dropping power - Added by Michael Williamson about 12 years ago
Hi Keith,
I have seen these symptoms before, and I'm pretty sure it's filesystem corruption related (I suspect udev related, not installing the /dev/ttyS* files due to a corrupted cached tarball of /dev which is by default stored off in /etc).
You probably will need to do some work on your filesystem image to set it up to be mounted read-only (you'll need to modify the bootargs to boot readonly). For the older BSP's (using 2008 angstrom), I made a pass at doing that with our reference base filesystem and made some rough notes here. It's not much, there are likely other references of doing this on the web as well. If you have a relatively small app and filesystem requirements, it might be easiest to just boot from a ramdisk image.
For the newest BSP, the process will be different due to the use of systemd. I haven't wandered down this path yet.
I'm fairly certain you're not damaging the hardware here, it's a bootup / startup corruption issue.
-Mike
RE: FS Corruption due to dropping power - Added by Keith Fletcher almost 12 years ago
Hi Mike,
Thanks for the reply. This is reasuring that it is a FS corruption problem. I have instigated a read only file system, based on your notes, and its seems to work, as in everything is mounted read only, and the application still runs.
Unfortunatley this is one of those problems you can only prove dosn't work, i.e it might be the next power off that causes problems - hence my tardy reply. However so far so good.
As part of your notes it is necessary to configure the fstab as read only, and the parameters passed from u-boot to the kernel. I am curious as to what the differnece is between the two, - do they protect different parts of the boot process ?
Keith
