[tlug] DiskOnKey boot success

[Frank Bennett <bennett@example.com>]

Dear TLUG,

I know that everyone is probably sick of my string of questions and answers
about my toils on the backup CD thingamabob.  But I've just had a very
interesting bit of success.

I have been using dd to run the El Torita CD image of the RepliCoaster system
onto the raw device node of a DiskOnKey, to use as a second-stage boot
source (the kernel does not have ext2 compiled in, to save a little space).

Just now, just for the hell of it, I plugged the key into the USB port of a
Dell Optiplex that is sitting on my desk.

It booted from the key.

I've seen docs on the Net stating that the M-Systems DiskOnKey (which this is
-- it's sold through IO Data as "Easy Disk" in Japan) will only work as a boot
device on Phoenix BIOS machines.  The OptiPlex has a Dell BIOS, but seems to
be happy treating anything it finds on USB as a CD-ROM, so long as it has an
iso9660 filesystem on it.

Booting in this way does not seem to work on my Sharp Mebius PC-SX1-H1; the
boot hangs until the key is removed or the BIOS times out and fails through
to non-USB devices.  The Sharp has a Phoenix BIOS installed.  Go figure.

There are some quirks to note in the DiskOnKey, in case anyone picks one of
these things up to play with.  It shows four SCSI disk partitions off the
shelf. You will find several alarming anomalies:

  o lots of SCSI errors (yes, Chris, this __is__ another of those whiz-bang
    gadgets you adore so much);

  o lots of complaints about the partitions when fdisk is run on the device;

  o A read only flag is put up by the device.

The problems can all be solved if you're reckless enough to try
the following:

  o There is a hack to get past the read only tag, that can be
    found here:
    
      http://www.stray.ch/articles/downloads/sd-patch-for-diskonkey.txt
    
    I applied this patch to the source for sd.c in the 2.4.16 kernel,
    and it worked.  Your mileage may vary.
  
  o You can ignore the partitions; just treat the raw device as
    a floppy disk.  It will work.  Honest.  :-)
    
  o In writing to the device with dd, the first write will fail.
    Just invoke the same command again, and the device seems to
    accept it.  You can then mount the device with the filesystem
    of the image.

It might be an interesting TLUG escapade to burn images onto a few of these
things and make a survey of Akihabara, seeing which machines will boot
successfully to Linux from key and which will not.  Try before you buy and all
that.

Same strategy should work from *BSD too -- maybe the survey could be treated
as a contest between code bases?

Cheers,
Frank
Nagoya