8. Creating an emergency boot floppy for ftape

This section was written by Claus Tøndering <ct@login.dknet.dk>.

Once you are the happy owner of a tape drive and several tapes full of backups, you will probably ask yourself this question: ``If everything goes wrong, and I completely lose my hard disk, how do I restore my files from tape?''

What you need is an emergency floppy disk that contains enough files to enable you to boot Linux and restore your hard disk from tape.

The first thing you should do is to read ``The Linux Botdisk HOWTO'' written by Graham Chapman <grahamc@zeta.org.au>. That document tells you almost everything you need to know about making an emergency floppy boot kit. The paragraphs below contain a few extra pieces of information that will make your life a bit easier when you follow Graham Chapman's procedures:

• You don't really need /etc/init, /etc/inittab, /etc/getty, and /etc/rc.d/* on your floppy disk. If Linux doesn't find /etc/init, it will start /bin/sh on your console, which is fine for restoring your system. Deleting these files gives you extra space on your floppy, which you will probably need.
• Find a small version of /bin/sh. They are frequently available on the boot floppies that come with a Linux distribution. This again will give you extra space. I'd suggest ash, which is extremely small (approx 62Kbytes), and yet very bash compatible.
• The /etc/fstab you include on your floppy disk should look something like this:

          /dev/fd0        /               minix   defaults
          none            /proc           proc    defaults
          /dev/hda        /mnt            ext2    defaults
          
  

  Once you have booted from your floppy, give the command:

          mount -av
          
  

• Make sure your floppy drive is not mounted when you access the streamer tape! Otherwise you may get the following error message:

          Unable to grab IRQ6 for ftape driver
          
  

  This means that you MUST load the floppy into a RAMDISK. This has the unfortunate consequence that the programs needed to restore the files from the tape can not be located on a separate floppy disk. You have two options here:
  1. You place tar (or cpio or afio or whatever other backup program you use) on your root floppy disk. (This is where you'll need all the extra space created in the steps above.)
  2. Before you start restoring from tape, copy tar (or cpio or afio or whatever) to your hard disk and load it from there.
• Apart from your backup program, you will probably need mt on your root floppy as well.
• Make sure your ftape device (typically /dev/nrft0) is present on your boot floppy.
• Finally: TRY IT OUT! Of course, I don't recommend that you destroy your hard disk contents to see if you are able to restore everything. What I do recommend, however, is that you try booting from your emergency disks and make sure that you can at least make a file listing of the contents of your backup tape.