SUMMARY: Reading past the eom on a 1/4" cartridge tape

From: Diane J. Donaldson (
Date: Wed Jan 27 1993 - 04:30:52 CST

Recently I wrote:

>From andie Fri Jan 22 10:46:58 1993
>Subject: Reading past the eom on a 1/4" cartridge tape
>Content-Length: 625
>Due to mixing up tar options, a user's tape was partially written
>over with garbage. I know there's about 30 megabyte of good stuff
>on the tape still, but I can't figure out how to get to it, if it's
>even possible. Nothing I try will get me past the EOM mark.
>Anyone got any hints? This user brought her tape from Brazil to
>the US so I'm *really* hoping most of her stuff can be recovered.
>I'm using a Sun 4/370 with a 150 meg cartridge tape drive, Sun OS
>4.1. Thanks in advance for any help you can give me.
> Diane Donaldson
> Department of Mathematics
> University of Maryland

I got a whole range of answers, from "it's impossible" to "it's simple".
As usually happens, it was neither. What finally worked was the following:

1. Go to the end of media (mt -f /dev/nrmt0 eom).
2. Start writing a long file (mt -cf /dev/nrmt0 long.file).
3. As soon as the tape starts writing, turn off the tape drive.
4. Eject the tape, turn the drive back on, insert tape and rewind.
5. Skip the first file on the tape (mt -f /dev/nrmt0 fsf 1).
6. Now start reading with either dd or a utility that can deal with
        bad tar files. I used badtar, but tarx was also recommended
        to me. I piped the output from badtar through tar using the
        i option to ignore checksum errors and was able to recover
        most of the tape.

I must admit, I was a little hesitant to turn off the power to the drive
in the middle of a write! But it definitely did the trick. By the way,
several people cautioned me not to just yank the SCSI cable as that might
damage the motherboard.

Thanks to all who responded, and especially to the following:
Andrew Watson <>
Russell Ruby <russ@MATH.ORST.EDU> (Birger A. Wathne)
Ted Nolan SRI Ft Bragg <>

                                                Diane Donaldson

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