Hey..
I was so foolish to do this... My friend gave me his hard disk to partition it.. I did that and plugged it into ma system for copying some files...
After mounting a drive, I tried changing the permissions of that drive using "chmod 777 -R /media/1 " ( that drive mounted at /media/1)

But seeing it was taking a long time, I exited the console and shut down the system..

Now, I am not able to 'su'... it gives the setgid error..
I cant login as root...
I checked the content of /var/log/auth.log

It says at one point ,

Dec 26 15:26:48 debian su[2946]: Successful su for root by hari
Dec 26 15:26:48 debian su[2946]: + pts/5 hari:root
Dec 26 15:26:48 debian su[2946]: bad group ID `0' for user `root': Operation not
permitted



What should I do now????????

Dude, before mounting the HDD, were you root? I mean, did you mount the HDD as root? The permissions would have been st accordingly. How many files did the HDD have? When you use <chmod> on a directory or on an entire drive, it takes some time. Again, this depends on the number of files that are on your HDD. You should not have stopped the process. Anyway, this is not a matter of concern. BTW, I thing you were trying to do some operation which is not permitted for users other than root.
One more thing, you cannot login as root on Debian, as it does not allow it. But this can be overcome by logging in via the terminal by removing the temporary file "/tmp/.X0-lock" - something like that. You can also do this: Goto Desktop->Administration->Users and Groups and then change the permissions for users regarding the mounting etc.

I don't quite get it... so you mounted it and copied some files to the drive, so you already had access. Why did you need to chmod it?
Did you copy with root? If you do that you should use cp -p to preserve ownership.

Also, you can interrupt a process by pressing ctrl-c in the console... no need to shut down.

Hey....
I did something and got ma 'su' back.. but some problems are persisting..

What I did is.. I used the debian rescue disk.. rescue mode... then typed 'su'.. became root..
Then i did 'chown root:root /usr/bin/sudo'
then.. 'chmod 4755 /usr/bin/sudo'
then.. 'chmod 4755 /bin/su'

i dono anything abt chown.. i copy-pasted it from some blog...

Then.. I booted back to Debian... now I can use 'SU'..

But still I cannot Login as root either from KDM or from console...

it says login:root
login incorrect

????????

and I am not able to mount CDROM drive in NORMAL USER MODE... If i run konqueror as superuser.. then I can mount it...

Here is ma fstab

# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
/dev/sda5 / ext3 defaults,errors=remount-ro 0 1
/dev/sda7 /mnt/Music vfat defaults 0 0
/dev/sda8 /mnt/Soft vfat defaults 0 0
/dev/sda1 /mnt/Win vfat defaults 0 0
/dev/sda6 none swap sw 0 0
/dev/hdb /media/cdrom0 udf,iso9660 user,noauto 0 0
/dev/hdd /media/cdrom1 udf,iso9660 user,noauto 0 0
/dev/fd0 /media/floppy0 auto rw,user,noauto 0 0
/dev/sda9 /mnt/New ntfs-3g rw,user,auto 0 0

And Deepumnit.. earlier I was able to login into debian as root...

I dont have gnome installed... I got only KDE....

Oskar. thx for that ctrl+c..

I was not able to copy after mounting as normal user.. then used chmod using 'su'.. there was a big folder already on the drive which i copied using windows xp( me using dual boot).. so got tired of chmod and did tht foolishnes...

Anyway.. after that I formatted that partition.. its permissions are hence not a concern for me..

Hey..No one to help me on the 'mount' issue?? and the root login problem??

Deepu.. I tried deleting the 'lock' file.. still the problem persists...