Hi Guys I thought I'd put this out to the experts as I know there seems to be the answers to "life the universe and everything"

so here goes
I have a small single board computer that runs Linux off of a USB. Well most of the time it does with most USB sticks, the unit is designed for desert installation so day time temps are high (Upto 55C in the Shade) so we have to have a higher spec USB stick (85C).
So we put our Milspec £50 usb stick in and now it only boots about 50% of the time. The times it doesn't it says

VFS: Cannot open root device “SDA2” or unknown-block (0,0)

Please append a correct “root=” boot option; here are the available partitions:

Kernel panic – not syncing : VFS : Unable to mount root Fs on unknown-block (0,0)

which looks to me like it can't see a partition or something like that, BUT WHY
Help

cheers Pete

Yeah the USB stick may be mil spec but is the PC can it handle the TEMP.... looks like the usb stick is not being found by the bios or the OS

How is the PC shut down, could it be that the file system is not being closed correctly

[Edited on 28/909/11 by mad4x4]

Taking the messages at face value and not knowing the exact boot process for the system, it looks like the USB stick has been found - no "No System Disk" error, going off the previous post, has the system ben soak tested at the expected operating conditions?
Also, why boot from a USB stick, wouldn't a CF (ATA) or SD card interface be more practical and more hardy?

Could be a dry joint in the sticks USB plug
Most our portable memory is now SD or Micro SD as we found USB sticks unreliable, Micro SD is sold graded for speed.

Thanks guys
Just to clarify the faults are at ambient temperature at normal startup and it seems to be fifty fifty if it starts or not. This works fine with the other memory sticks we have used (3 other makes) but the mil spec one is flaky. We have just started testing on this ( functional,emc,halt) unit and this is causing a few issues and I was kind of hoping someone may have seen something like it.
The intention is in the near future to get rid of the SBC and the USB but for now we need to fix what have.

Thanks again
Cheers pete

Try the stick in a normal PC and see what happens.
Also, you didn't buy it from Ebay did you, is it genuine?

quote:

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Originally posted by watsonpj
Thanks guys
Just to clarify the faults are at ambient temperature at normal startup and it seems to be fifty fifty if it starts or not. This works fine with the other memory sticks we have used (3 other makes) but the mil spec one is flaky. We have just started testing on this ( functional,emc,halt) unit and this is causing a few issues and I was kind of hoping someone may have seen something like it.
The intention is in the near future to get rid of the SBC and the USB but for now we need to fix what have.

Thanks again
Cheers pete

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They are genuine and work fine in a pc, but maybe i'll test a few more tomorrow just to make sure.

Cheers Pete

I would suspect an iffy USB/chipset driver...

Stephen
(running a Media PC booting from Compact Flash)

I suspect you need to add additional time to allow the USB devices to stabilise before it tries to boot off the stick.

See this page: https://help.ubuntu.com/community/BootFromUSB

Specifically:

quote:

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There is one small problem before we carry on: USB drives take a few seconds before they are engaged properly by Linux, and your boot would fail before the drive becomes accessible. To sort this, we need to tell the initrd to wait a few seconds before it gets carried away and fails. You can do this by running:

gksudo gedit /etc/initramfs-tools/initramfs.conf

Now add these lines at the very top of the file:

### This makes the bootup wait until any USB drives are ready
WAIT=15

Then save the file and exit the text editor.

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Thanks Ben I'll give it a go tomorrow

Ben you get the expert badge today it works fine now

Thanks Pete