Hi, I just re-installed Debian Squeeze 6 (in expert mode which I found very useful), don't remember if I was requested to set root/user passwords - maybe system used user name and passwords from previous installation because I left home directory unchanged?

To start Debian, I need username & password on desktop but old ones are not working ("authentification failed"); no other options on desktop. I know how to use partedmagic program to access file system, but not sure what to do? Many thanks for suggestions.

You can look for the line that starts with 'kernel' in grub and append 'init=/bin/bash' this will boot into a single user mode with you as root where you can change root password by issuing 'passwd'.
Look for some info in log files in /var/log. No matter what the installaton is Debian will ask for a root password.
Hope this helps.

Many thanks.

I managed to get into grub edit mode and saved extra "init=bin/bash" line, but still getting user-login-password screen, and this line is not on grub edit list on the next boot. Debian time is 10h in the future, but cant be corrected in login desktop (hope this is not a problem).

var/log shows user name (which is correct)and then "no such username". It also shows password change fact but not actual password.

Under grub directory, there is only one starts with "kernel" file: kernel.img but I found no way to open/edit it.

More ideas?..

The 'init=/bin/bash' has to be appended at the bot time. This is when the bootloader loads, when you have the grub screen with all the boot options.
In case this is not possible boot with a live cd - or boot with debain with rescue mode - and edit the /etc/passwd and delete the charaters ':0:0:' after the root entry (be careful that is our root password. You would next nned to delete the encrypted password from '/etc/shadow' after the root: entry (this is the encrypted password). The root password would then be blank.
I just thought of an easier way, boot with a live cd go to /etc/sudoers and uncomment the last line (works for slackware) and then you can log in as yourself and just run sudo, that should do it.
MAKE A BACKUP OFF THE FILES YOU EDIT. MAKE SURE THAT THE BACK UPS ARE VERIFIED.
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