Is anybody *USING* ANSI tapes on UNIX (label handling)

[Johan Finnved]

There has been some talk on the net about protecting people from writing
on wrong tapes. So far it has been assumed the nobody mounts the wrong
tape on a tape drive which is not always correct.

There has also been a package for reading and writing ANSI-tape recently
but without multiple volume handling and without enforcement of
protection.

I think that an implementation of the ANSI standard for Tape Labels and
File Structure for Information Interchange (X3.27-1978) would solve
several problems. Most notably positive tape identification and
continuation of big files on multiple volumes (without having
applications to limit their output).


I think that this could also solve the problem of two users accidently
using the same tape drive.

Possible implementation suggestions:

The driver is helped by a tape managing program which handles labels and
blocks-unblocks data. Data is moved between tapes and files or pipes.
The raw device is not accessible by ordinary users. The driver allows
only one open at a time, and the server does only one open and thus
knows that nobody can interfere with its tapehandling. It starts by
rewinding the tape and checking its volume label in order to make sure
that this user (real uid) has really the right to use this tape. There
has to be IOCTL:s for tape positioning, rewinding ,writing of tapemarks
and for forcing writes after EOT. I think it is most efficient to allow
reads until a few blocks after EOT and writes up to EOT and then let the
first after EOT has been seen return an error (or zero count) and then
have an ioctl that allows you to write a few blocks more to make the
volume finish correctly. The tape managing program is set-uid "tape".

Has anybody assigned IOCTL subfunctions for the above magtape commands ?

Does anybody have ideas on what to put in the fields for Owner
Identifier (in VOL1 lables), Accessibility  (In VOL1 and HDR1-EOV1-EOF1
labels) and System Code (in HDR1-EOV1-EOF1 labels) ?

Maybe somebody has already assigned codes in some other system? (VMS?)
Unfortunately the fields seems to be too short for domain type
identifiers (site.subdomain.subdomain.DOMAIN)

		Johan Finnved, Objecta, Sweden <jf at sal.UUCP>