by Kulbir Saini | Grub, Hacks, HowTo, Linux, Security in , ,

How To: Recover/Crack Root Password when Grub is Locked

The only essential thing is that you should have a Linux boot CD of the same operating system for which you want to crack root password. Some other Linux boot CD may work in some cases. If system is able to boot from the CD, it will take you to a command prompt as shown.

boot:

Type ‘linux rescue’ at this command prompt and enter as shown

boot: linux rescue [Enter]

It will take you to some interface with some questions, answer them properly. The system will go to temporary command prompt. Then issue the following commands

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[bash$] chroot /mnt/sysimage [Enter]
[bash$] cd /boot/grub [Enter]
[bash$] vi menu.lst [Enter]

Now in this file you can see a line beginning with the word ‘password’ remove this line and save the file.

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[bash$]exit
[bash$]exit

Now system will be rebooted and you can see the grub without a password. Don’t forget to remove the CD.

Press ‘e’ at boot screen and again by taking the pointer to the second line press e. Now you can see yourself on a command prompt. Remove ‘rhgb quiet’ from there and write single and press enter.

Now you will come back to the boot screen. Press ‘b’ and system will appear to boot and leave you in command line interface like this.

-bash2-$

Just type passwd like this

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-bash2-$ passwd [Enter]
new password:
retype new password:
passwd: All authentication updated successfully.

Now you have set a new password. Now exit from the shell and system will boot properly in graphical interface.

-bash2-$ exit [Enter]

If there is any error in the procedure please post your suggestions.

 

11 thoughts on “How To: Recover/Crack Root Password when Grub is Locked”

  2. hi !!
    I want to know about how to crack root password which is also grub password protected.One main problem is that the system has no cd drive .Any method to crack though USB ???

  3. @Jaq
    Yes. If you have installed a small Linux distro for example Ubuntu or Damn Small Linux in you USB drive. Now, you can boot from your USB drive to the Linux distro. Now, mount the partition allocated to /boot or / from the other hard drive to /mnt with write access. Now, the job is very easy, just modify the menu.lst file in /boot/grub/ as described above.
    Hope this helps in right spirits.

  4. sir, i have no installation cds , and i don’t know the passwd of root, and someone has set the root passwd..
    so , how could i get into the root
    or my system….

  5. i don’t know the root passwd, and someone has set the grub passwd….
    an di don’t have any installation cds …
    how could i get into the system.???????????/

  9. How to login to linux server with root ? ( I don’t have any login in that server ). I know the opened port, but I don’t know how to use it to hack the server.That server using Trustix or CentOS Linux. Thanks.

  10. i entered the rescue mode,and got the shell also . but the problem is that when im typing ‘ chroot /mnt/sysimage’ ,is is showing an error ‘/sbin/sh not supported.what shall i do now ?
    plz email me the solution

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