Unlike mainframes where a tape recognition daemon (they aren't really called that but function that way) is used to ID a tape header, HP-UX doesn't have anything like that. Instead, you can use the guessing program called file. File is a magic program. OK, it uses a file call /etc/magic which is a series of codes to tell file how to match up something at the beginning of a file (or device file) with common formats. So the commands:
mt -t /dev/rmt/0m
dd if=/dev/rmt/0m of=/var/tmp/tapeid count=2
file /var/tmp/tapeid
should tell you about the tape, assuming that it is in a 'well-known' format like tar, cpio, etc. (note that /dev/rmt/0m is an example--use the correct device file for your system) It is IMPOSSIBLE to determine if the tape was created with dd since dd is a raw copy of
. Also, tape formats from mainframes (ie, ANSI or IBM labeled tapes) are not recognized by file. However, you can see if it is a mainframe labeled tape by using xd as in:
mt -t /dev/rmt/0m
xd -xc /dev/rmt/0m | more
If you see something like VOL as the first 3 characters and subsequent header lines like HDR1, HDR2, etc then you have an ANSI labeled tape. If the characters are strange, it might be in EBCDIC mode so use something like this to translate:
mt -t /dev/rmt/0m
dd if=/dev/rmt/0m od= count=2 conv=ebcdic | xd -xc
If thisa looks like VOL HDR etc records are present, you have an IBM standard label. The bad news about ANSI or IBM standard laebls is that there is nothing in HP-UX that can read the data and make sense out of it. If the tape contains fixed length records, you can probably play with mt (for positioning the tape) and dd to do a raw copy and translate from EBCDIC if necessary. But if the format is variable length, you'll have to write a program to interpret the records, essentially the basics of a mainframe restore program.
Bill Hassell, sysadmin
