not panicking (LONG -- was Re: Problem with putting a process in the 'background')

[David B. Thomas]

The theme of this posting is: don't panic.  You probably don't need to
reformat and reinstall software as often as you think.

picano at en.ecn.purdue.edu (Silvio Picano) writes:

>Ok, so I placed my executable in /etc and called it from
>rc directly.  Wrong: the reboot procedure failed (it never
>returned: a blank screen resulted with "Working" in the corner 
>'forever') and I needed to reload ALL the software (argh).

I've done this too, and it's easy to convince yourself that you have
no alternative but to reformat and reinstall everything from the distribution
disks.  But often this is not the case!!

You can run unix off of the floppy drive, and poke around on the hard
disk to undo such mistakes.  Just boot the FLOPPY BOOT DISK, then
insert the FLOPPY FILESYSTEM DISK when prompted, and then (this is
important) hit DEL (shift-esc) at the very first prompt.  Do not
confirm this prompt or you WILL reload everything from scratch.

>From there, you have some limited unix functionality.  ls -R / to
see what's there.  you can mount the hard disk with "mount /dev/fp002 /mnt"
and unmount it with "umount /dev/fp002".  When you're ready to reboot,
type sync, then go for the button or type reboot.

If you're a bit industrious, make yourself a better floppy filesystem disk
(or several).  Copy the original floppy filesystem disk, then mount it
and overwrite /etc/profile (that's /mnt/etc/profile !!) with one
line: "/bin/sh".  That way, you'll get a shell right off.  There's
some room to spare, and I recommend adding (in order of usefulness):
	fsck
	dd
	packdisk (by andy fyfe)
	rmdir
	afio

Armed with a disk like this, you can recover from about anything.  Armed
with a disk like this and a good backup, you'll never lose much.

More comments along these lines:

1. You need not install the 12 foundation set disks before restoring a
  full backup you have made.  Put in the first backup disk when you would
  normally put in disk 5 of the foundation set.  Or, better yet, boot
  floppy unix, get to the shell prompt, and type the cpio command yourself:
	cpio -iBcdvu < /dev/rfp021
  Be in the root directory of the mounted hard disk (/mnt) at the time.

2. You need not reinitialize and reinstall just to lock out bad blocks.
  With bf and ncheck -i, you can find out which files are affected.
  Then you can use the diagnostic disk to lock out the bad blocks.
  In fact, you can use dd to surgically recopy the data from the old
  block onto the new.  Kids, don't try that at home!

3. You can boot diagnostics from the hard disk, if you have the fancy
  loader.  Mount the diagnostics disk and copy s4diag (I think that's
  the name) onto your hard disk.  When you want to boot diagnostics,
  tell the loader to boot from the hard disk, and that file name.


Sorry for spewing... this is stuff that I learned "the hard way",
so I thought it might be useful to post.

						little david
-- 
Bottom of stack = 0x40000
Stack pointer   = 0x3fffe
Don't push it!