[ILUG] USB Mass Storage

[Rick Moen]

Quoting James Cooper (jac1 at student.cs.ucc.ie):

> I've a question about using a DiskOnKey with  linux.

Hey, just like the one I wrote about in my Linux Journal article!

> Basically, what options do i need to select when compiling the kernel?
> (The default RedHat 7.3 kernel doesn't support it).

1. For heaven's sakes, you shouldn't be running RH 7.3 at this late
   date.  Update to Fedora.

2. That not withstanding, you can and should get updates to your ancient
   kernel.  E.g., look at the 2.4.x entries here:
   ftp://linux.stanford.edu/pub/mirrors/updates-7.3/i686/  
   Even though those kernels will almost certainly be subject to at
   least two local exploits, they're still likely better than what you
   have.

3. I can't post my LJ article, as that would be injurious to SSC's 
   commercial rights, but I think I can quote from it:

   Linux's USB support starts with the kernel needing to recognise your
   motherboard's USB chipset, which will be a UHCI (Intel) or OHCI-class
   (Compaq and others) device, requiring the usb-uhci or usb-ohci kernel
   driver, respectively. (Both also will need the usbcore driver.) If
   lspci -v returns USB information that includes I/O ports at, then you
   have a UHCI controller. If the returned USB-controller text includes
   Memory at, then it's OHCI.

   When you're done tweaking module loading (if necessary), the output of
   lsmod should include all three required drivers. For example, my
   laptop machine lists:
Module              Size  Used by    Not tainted
usb-uhci           20676   0  (unused)
usb-storage        97120   1
usbcore            48000   1  [usb-uhci usb-storage]
[...]
   If you're running a 2.3.38 or later kernel (and you should really
   upgrade to 2.4.x or later, at this point), you also should add the
   following line to /etc/fstab to enable USB device-tracking:
none  /proc/bus/usb  usbdevfs  defaults  0  0

   After this, type mount -a. Now, you're all done except for mounting
   the actual mass-storage device. The above step does not mount the
   device--usbdevfs is a strictly abstract support filesystem similar to
   /proc, used by the USB subsystem.
[...]
  I created a mountpoint directory of /mnt/fob to hang the flash drive
   off of it.
[...]
# mount -o uid=1000,gid=1000,noatime -t vfat \
 uid=1000,gid=1000,noatime -t vfat \
/dev/sda /mnt/fob/
[...]
   All of those mount options can and should be put in /etc/fstab:
/dev/sda  /mnt/fob  vfat  uid=1000,gid=1000,user,noauto,noatime 0 0
[...]
guido:~# mount -t vfat /dev/sda1 /mnt/fob

> Everytime i've tried to do it so far, writing to the device seems to
> work (no command line errors) but nothing is physically written.

That's because it mounts read-only, initially -- even though you specify
otherwise.  (That turns out to be because the device itself is a little
dodgy, and doesn't give correct responses when queried about its
capabilities.)  You can and should remount read-write to fix that, after
the initial mount.

Warning:  Don't have it mounted read-write any more often than you must,
and use the "noatime" option when you do -- because of NAND flash
devices' wear characteristics.  If you need more information, subscribe
to Linux Journal and read my article on-line among the back issues.

-- 
Cheers,                   The cynics among us might say:   "We laugh, 
Rick Moen                 monkeyboys -- Linux IS the mainstream UNIX now!
rick at linuxmafia.com       MuaHaHaHa!" but that would be rude. -- Jim Dennis