Some guidelines for filesystem backup

[Alan H. Mintz]

In article <7558 at ucdavis.ucdavis.edu>, tuck at iris.ucdavis.edu (Devon Tuck) writes:
> In article <4 at icdi50.UUCP> Steve writes:
> >
> >Does anybody know of a utility that will back up an entire disk drive to
> >streaming tape under SCO Xenix or Unix...
> >
> 
> II)  If you want a backup of the entire file system, and...
> 	D) You have made a "Bootable, root floppy" with "mkdev fd" after
> 	   your tape driver was installed in the kernel, then mounted that
> 	   floppy and copied all useful commands such as (restore, restor,
> 	   more, ls, mount?, umount, mkfs, any necessary tape programs) onto the
> 	   drive so that you can boot from this floppy to divvy your disk and
> 	   restore your filesystem. (NEVER TRY TO RESTORE TO THE SAME FILESYSTEM
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 	   FROM WHICH YOU BOOTED) and (Always do an "fsck -s /dev/hd0root" after
           ^^^^^^^^^^^^^^^^^^^^^
> 	   this restore)

While this is the true "party line" as told by SCO, it is possible (not 
necessarily reliable) to restore an active root filesystem with SOME tape
drivers on SOME tape drives on SOME versions of XENIX. If you are stuck
in a position of having to do this, do the following:

1) Create a rudimentary bootable filesystem on the hard disk. Install enough
of the O/S to be able to link the tape driver into the kernel.

2) Do the restore ("restor fr /dev/erct0 /dev/rroot" or the like...). 

3) THIS IS THE IMPORTANT PART. Wait for the tape rewind at the end of the
restore (this generally requires that you have an "ear" for the particular
drive sounds). While the tape is rewinding, TURN OFF THE POWER.

Believe it or not, this results in a completely clean filesystem. It seems that
the drivers under which this method works do not allow a sync() to take place
until they are done restoring and they are not considered done until the tape
has rewound.

Note that I present this simply as a matter of interest and a last resort. I
would not want to rely on this. It was, unfortunately, required to be done this
way on a system that had a certain (stupid) driver that did not seem to want
to run from a floppy filesystem. The (VERY popular) manufacturer of said
drive could not offer any suggestion and admitted that they had never tried 
running it from a floppy filesystem !
-- 
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