[atlas] USB drive

Hi Michael,


> but on further inspections do not contain a valid magic number in their superblocks, so they are effectively unformatted. I would therefore suspect that they are not being used by the probe.
> 
> Now the question:
> What is the correct layout supposed to look like (primary/secondary, size, ID, FS-type)? I would like to get my probe back up and running.

In general, the probe doesn't care what is on the USB stick. So wiping
or formatting the stick is not needed.

There is at the moment one rare exception. The filesystem can go corrupt
to the point the fsck hangs. In that case, wiping the entire USB stick
will help.

To get the probe to reinitialise the USB stick, the correct procedure is
to power on the probe without USB stick and then insert the USB stick
after a few minutes (10 to be safe).

The procedure suggested by Gert Doering will also work. But should not
be necessary.

The filesystems on the UDB stick are encrypted, that why you can't find
any valid magic numbers.

> Bonus question: 
> What can I expect to find in point of files/data on the drive, that would tell me whether the probe was working correctly until I cut power and removed the drive?

You cannot find anything on the drive. Only the probe has the encryption
keys.

Currently the probes use an ext2 filesystem, because it is simple and
seemed to work well enough. It worked well in artificially power cycling
the probe for period of time. Of course, reality is worse.

At some point I'll try to experiment with adding journaling to see if it
makes a difference.

Philip