Only one backup per tape? Really?

[W. Paul Zola]

In article  <NELSON.90Dec12212501 at image.clarkson.edu> 
	    nelson at clutx.clarkson.edu (aka NELSON at CLUTX.BITNET) writes:
}I've got two filesystems to back up, and only one tape drive, and I'd
}like to do unattended backups.  Can I really only back up one
}filesystem per tape?  Well, of course I mean, will I be able to *restore*
}from a tape with two backups on it?
}
}--
}--russ (nelson at clutx [.bitnet | .clarkson.edu])  FAX 315-268-7600
}It's better to get mugged than to live a life of fear -- Freeman Dyson
}I joined the League for Programming Freedom, and I hope you'll join too.


You don't say if you are using an SCO system or not, but from the
newsgroup I assume you are.  The following article from the SCO
Information Tools database should help with your problem.  

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How to store multiple archives or backups onto a single cartridge tape

KEYWORDS: no rewind QIC cartridge tape drives multiple archives tar cpio 
	  backup /dev/nrct0 xenix

RELEASE: SCO XENIX Release 2.2 and later
         SCO UNIX System V/386 Generic

PROBLEM: How can more than one backup, cpio, or tar archive be written
         to a single tape cartridge?

SOLUTION: The no-rewind device allows the SCO XENIX user to write and read
          QIC tapes without automatically rewinding them, as is the default for
	  other tape devices.  Using the no-rewind tape device /dev/nrct0,
	  multiple files or archives can be written to a tape.  For example,
	  the following three commands, if given in succession, will write
	  three tar archives to the tape currently in the tape drive:

                        tar cvbf 20 /dev/nrct0 /a 
			tape -c wfm
                        tar cvbf 20 /dev/nrct0 /b 
			tape -c wfm
                        tar cvbf 20 /dev/nrct0 /c 

          Once the desired archives have been written, the tape must be rewound
          before it may be read.  Use the "tape rewind" command to rewind the
          tape.  After multiple items have been written, the "rfm" (read file
	  mark) option to the tape(C) command can be used to seek to the 
	  desired item.  To retrieve the third tar archive written by the
	  example commands above, use the following command:

              tape -c rfm;  tape -c rfm; tar xv6

          The no-rewind device may be used in the same way to read and write
          multiple cpio(C) archives, or backups from the backup(C) command.

NOTE: There is no no-rewind device available for Irwin tape drives, so the
      above techniques apply to quarter-inch cartridge (QIC) tape drives only.


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I hope this helps with your problem, and is of general interest as well.

-
Paul Zola			Software Support Engineer 
				paulz at sco.COM 
We only know in theory what we are doing.   - Kate Bush
    DISCLAIMER: I speak for myself, and not for SCO.