Very Computer

by **bl..** » Wed, 02 Nov 1994 02:36:31

Hi. While I'm not a regular to these newsgroups, I do know of them. A
colleague of mine just wiped out his disk and called me for help. Alas, I am
not a Unix guru, so I cannot help him. I promised I would present his problem
to the Usenet world, though. Here are the details.

System: SUN IPC, upgraded to IPX
Opsys: SunOS
Version: 4.1.3
Problem statement:
User/owner of above workstation did a "newfs" instead of a "mount". (Even
I know that means trouble.) Questions:
1) Is there some way to recover the file system? (I know, the file system is
there, just logically empty; can he recover the *previous* file system?)
2) Is there a utility which can scan a disk partition (the term raw mode
comes to mind) and pick out ascii files, directory files, etc., possibly
copying them to other disk partitions?

As I said, my friend does not have Usenet access. Please direct your replies

to him. I will also check back in this newsgroup in a few days to see what
others have posted. Thanks.

Larry Bleau
University of Maryland

301-405-6223

>System: SUN IPC, upgraded to IPX
>Opsys: SunOS
>Version: 4.1.3
>Problem statement:
> User/owner of above workstation did a "newfs" instead of a "mount". (Even
>I know that means trouble.) Questions:
> 1) Is there some way to recover the file system? (I know, the file system is
> there, just logically empty; can he recover the *previous* file system?)

And he doesn't have a backup? The file system structure is most likely
gone, especially if the previous one and the new one were created with
the same newfs parameters. If he didn't use the same parameters then
some of the file system structures may not have been overwritten, but
getting to them is hard. You basically have to look for superblocks
that aren't where they belong.

If he did use the same parameters then, the inodes and cylinder group
information has been overwritten. All you can do is scan the disk looking
for "interesting" blocks. On gatekeeper.dec.com in /pub/sysadm is a
compressed tar archive called recover.tar.Z. The program there will
scan the free list of a disk looking for text blocks and will write
them to stdout. This output could be redirected to a file on a different
disk and then filtered by hand later.

The data analysis routine is uses could be customized to look for other
things. I suppose it may be possible to invent an algorithm that will
recognize directory blocks.

>Larry Bleau
>University of Maryland

>301-405-6223

--

Very Computer

Recovering lost file system: how?

Recovering lost file system: how?

Recovering lost file system: how?