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Re: Quantum LTO 4 tape drive and Cygwin 1.7?


Thanks for your reply. My responses below...

Corinna Vinschen wrote:
On Oct 20 15:24, Jeffrey C. Smith wrote:
I'm trying to use tar from Cygwin 1.7 Beta on a Win 2008 R2 machine to backup some files to a Quantum LTO 4 SAS tape drive. I've tried all the usual POSIX paths (/dev/nst0, /dev/st0, /dev/st1, etc.) as well as some other variants (\\.\tape0) with no joy. tar fails with a "No such file or directory" error.

The right way to access tapes is to use the /dev/stX or /dev/nstX variation. Using the Windows path \\.\tapeX will not work as expected.


Typically the first tape drive attached to a Windows machine is
called "tape0", which is what Cygwin tries to access when specifying
/dev/st0 and /dev/nst0.

If you want to see the name of the tape drive on your system, just open
the Device Manager and then open the device tree element "Tape drives".
You should find an entry named like your tape device, for instance
"QUANTUM ULTRIUM 4" or something along these lines.  Double click opens
the Properties dialog.  There's a tab called "Tape Symbolic Name".  Open
it.  It will show you the string "tapeX" with X some number >= 0.  THis
is the same number to use in Cygwin.

OK. I'm looking at the window titled "Quantum LTO 4 Tape Drive Properties" under the tab titled "Tape Symbolic Name" and the tape name appears to be "Tape2147483646" (that's a long way from tape0!).

I started Cygwin as administrator and tried this:

$ mt -f /dev/nst2147483646
mt: /dev/nst2147483646: No such file or directory

$ mt -f /dev/st2147483646
mt: /dev/st2147483646: No such file or directory

I just mounted a tape drive to my Windows 7 machine and it showed up as
\\.\tape0 in the device manager.  I could use mt(1) on it:

  $ mt -f /dev/nst0 status
  drive type = STK 9840
  drive status = 1107361792
  sense key error = 0
  residue count = 0
  file number = 0
  block number = 0
  Tape block size 65536 bytes. Density code 42 (unknown).
  General status bits on (410b0000):

Using the correct /dev/[n]stX, I never saw a "No such file" error yet.
What I can easily reproduce is a "Permission denied", though.  Under
UAC, if you're using the standard command line you don't have admin
privileges.  More exact, you don't have backup/restore privileges.
Accessing a tape drive without these privileges fails.  If you want
to access the tape drive, you have to start cygwin elevated.

Do you think the tape name "Tape2147483646" is a problem? At the bottom of the "Tape Symbolic Name" tab there is a comment that says "Symbolic name such as Tape0. It would seem that the name "Tape2147483646" is somewhat out of the ordinary. BTW, 2147483646 is -2 in a two's complement 32 bit number. Could this be some type of overflow/underflow error?

Also, this is Windows 2008 R2. I'm told that 2008 R2 and Win 7 share the same code base. Is 2008 R2 an officially supported platform for 1.7?

I really appreciate your help. If there is anything I need to do on my end to help resolve the issue please let me know.

Jeffrey C. Smith                                   Phone: 512.692.7607
RevolutionONE                                      Cell : 512.965.3898

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