Recovering lost file system: how?

Recovering lost file system: how?

Post 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

 
 
 

Recovering lost file system: how?

Post by Alan Rollow - Dr. File System's Home for Wayward Inode » Thu, 10 Nov 1994 09:45:08



>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

--


 
 
 

1. Kernel lost, system still running - how to recover?

Hi

Recently I have started administering an rs6000 running AIX. First
thing I want to establish a proper system backup, using th e mksysb
utility. I get a lot of errors, which I have tracked down to the file
/usr/lib/boot/unix_up (the kernel?) having a size of 0 (zero) bytes.

The system is still running, but giving that I suspect the kernel is
missing I am very reluctant to start experimenting too much because I
may not be able to boot the box :-(

The question is

 . Can I rebuild/regenerate a kernel? If so, how?
 . The kernel presumably comes from one of the installation cd's. Can I
   reinstall the kernel image from the cd? If so, which one and how?

Thanks for your time,
Jacob.

uname -svr
AIX 4 2

Attached: Output from lppchk -c

lppchk: 0504-208  Size of /usr/lib/boot/unix_up is 0, expected value was 2445410
.
lppchk: 0504-212  The checksum for file /usr/lib/libdcepthreads.a is 43340,
        expected value is 17160.
lppchk: 0504-212  The checksum for file /usr/lib/libdcelibc_r.a is 28607,
        expected value is 31331.
lppchk: 0504-206  File /usr/lpp/atldd/atltrc could not be located.
lppchk: 0504-206  File /usr/lpp/atldd/mtevent could not be located.
lppchk: 0504-206  File /usr/lpp/atldd/mtlibio.h could not be located.
lppchk: 0504-206  File /usr/lpp/atldd/trcatl could not be located.
lppchk: 0504-206  File /usr/lpp/atldd/mtlib could not be located.
lppchk: 0504-208  Size of /usr/ccs/bin/dbx is 4556, expected value was 4516.
lppchk: 0504-208  Size of /usr/ccs/lib/xpass is 193622, expected value was 19348
2.
lppchk: 0504-208  Size of /usr/ccs/bin/make is 87402, expected value was 87314.
lppchk: 0504-208  Size of /usr/ccs/lib/cflow1 is 200936, expected value was 2007
80.
lppchk: 0504-208  Size of /usr/ccs/bin/m4 is 36300, expected value was 36332.
lppchk: 0504-208  Size of /usr/ccs/lib/lint1 is 201134, expected value was 20097
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