how to recover root passwd if bootloader password in not set

jindalaman1987 · 03-08-2007, 10:17 AM

I am using fc5. i havent set the bootloader password for the system
could anybdy tell me how can i recover the root password of my system

thanks.

macemoneta · 03-08-2007, 10:50 AM

When you boot to grub, edit the kernel line (follow the prompts under the box: 'e' to edit) and add the option 'single'. For example:

Code:

title Fedora Core (2.x.y)
        root (hd0,0)
        kernel /vmlinuz-2.x.y ro root=LABEL=/ quiet single
        initrd /initrd-2.x.y.img

Then boot, and the system will be in single user mode at a root prompt. You can issue the 'passwd' command to change the root password and the reboot.

passwd
...
shutdown -r now

pixellany · 03-08-2007, 12:37 PM

For completeness--recovering the root password is not related to whether you have a bootloader password set.

rickh · 03-08-2007, 12:42 PM

As near as I can tell, that won't work on a current installation of Debian Etch, and I wouldn't want it to ... If someone can verify that I am wrong, I'd appreciate it.

macemoneta · 03-08-2007, 12:47 PM

The OP noted that FC5 is in use, and it certainly will work on that release. Any system that uses lilo or grub as a boot loader will allow this operation (I assume Etch uses one or the other).

This is not a security issue; physical access to a machine implies absolute control.

rickh · 03-09-2007, 01:11 AM

I have not been able to do it. I only added to this thread because I have not gotten any further responses on the one linked here. I am simply looking for verification one way or the other.

macemoneta · 03-09-2007, 09:49 AM

I see from the other thread that Debian requires a password even in single user mode. That sounds like security, but it's not. Since you have physical access, boot Knoppix or any live Linux CD/DVD), open a terminal, and change the (liveCD) root password. Edit /etc/shadow (the liveCD one) and copy the hash to the /etc/shadow on the system root for the real system. You've just changed the password, the old fashioned way.

rickh · 03-09-2007, 03:00 PM

I acknowledged on the other thread that it could be done with a live CD ... As I view it, that requires considerably more sophistication than the method described above. Given time, certainly, root can be compromised, but not in 30 seconds or less by a relatively unknowledgable user..

macemoneta · 03-09-2007, 03:06 PM

Quote:

...but not in 30 seconds or less by a relatively unknowledgable user..

I guess you're defining that to be anyone that has never heard of nor had access to the Internet. Not too many left, I'm afraid.