Using the DLT Drive

Below is a basic HOWTO for writing a DLT tape on the node grus (in room 501B, the Sun room).

1. Solaris tar (/usr/bin/tar) doesn't like to write tar files larger than 4 GB. Use /usr/local/bin/tar (gnu tar).

2. The default block size for tar (1 block=512Kbytes) is only 20 blocks. This makes a little marker on the tape and makes it slow to read and write. You need to reblock to maximum size of 16384 blocks

3. Put tape in - lift door, insert tape, lower door.

4. Wait for blinking to stop - change density to desired density by pressing button on left side. To get maximum density and thereby maximum capacity of 40GB, compress, density override lights should all be lit.

5. We'll assume that the name of the dlt drive is: /dev/nrst27.
   If you're somewhere other else, or if we move the drive and forget to change these instructions, you'll need to figure out the dlt's device name which corresponds to "Ncbn" (which means: compressed, no-rewind; N=the drive ID; suppose you don't know N (it's probably 0 or 1)). To find which name to use:

   ls -l /dev | grep cbn
   lrwxrwxrwx 1 root root 8 Feb 28 2001 nrst27 -> rmt/1cbn
   lrwxrwxrwx 1 root root 8 May 3 2000 nrst28 -> rmt/0cbn
   

   In this example, it returns two names: /dev/nrst27 and /dev/nrst28. Check each to see where your tape is found:

   mt -t /dev/nrst27 status

   If no tape is found (and you have loaded it) - you have the number wrong, try nrst28.

6. Now to write the tape! We use dd to reblock tar's output with a larger block size. In this example, suppose we are copying all files from /f/kelley and below in the directory tree:

   /usr/local/bin/tar -cvf - /f/kelley | dd obs=16384b of=/dev/nrst27

7. To rewind the tape:

   mt -t /dev/nrst27 rewind

8. To get a listing of the tar files created:

   dd ibs=16384b if=/dev/nrst27 | tar -tvf -

9. To extract the files:

   dd ibs=16384b if=/dev/nrst27 obs=20b | tar -xvf -

   (Thanks to Zo Webster for putting these instructions together!)

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   To suggest changes, additions, clarifications in this documentation, contact Central Services: central@astro.