Posted by: paragon | November 27, 2006

Lost root level password on Linux CentOS


I have lost my system (centos 4.3) root password,
I have change try to change the root password by the command “change password” but I receive the message “error 32 you must be authentificated”

Thank you,


You need to boot into single user mode (by sitting in front of the actual computer)

Then you can reset it from there.

Quoted from another post:

“Boot into single user mode. You can do that by modifying the grub boot option on startup.

1. Press ‘e’ to edit startup
2. Use the arrow keys to highlight the kernel line and pres ‘e’ to edit the parameters
3. At the end of the line, add the word ‘single’ (without the ‘) and press Enter
4. Press ‘b’ to boot the system

You will be dropped directly into a bash shell as root and can change the password. You can also access your file system from there. You will not have any network access while in single user mode though.”

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  1. Linux with LILO configured boot …

    Using lilo, press esc when you get the lilo menu, and run “linux single”. that will load you into single user mode (runlevel 1) then just use “passwd” to set a new root password.


    Dave Safley

    “World Class Internet Services”

  2. More stuff on root level password changes:

    Also check out this security focus article:

    This article will discuss the second weakest layer of computer security, Physical Security1. As we’ll see, any attacker with physical access to a computer, a little ingenuity, and sufficient time, can compromise the system. By way of example, I’ll demonstrate attack and defense on a Red Hat Linux box and show how you might slow down, or even prevent, these kinds of attacks. You don’t need a Linux machine, or even technical responsibility, for this article to be useful. This problem is independent of operating system and this article is general enough to be useful to every level of computer user. Be warned, though – you’ll probably only be able to slow down a determined attacker.


    Dave Safley

    “World Class Internet Services”

  3. One tip…

    At least when using Grub on CentOS 4.x

    1) At the boot screen, enter e
    2) Scroll to the kernal that has -up after CentOS-4 i368
    3) press e
    4) Scroll to the kernal boot string and press e
    5) Add a space and the word single at the end of that string
    6) Press the enter key then b to boot

    You will be booted into a Bash Shell

    Enter passwd to change the root password

    Clearly you need to have your box in a secure Data Center or follow some of the tips to place a password on Grub or Lilo etc..

  4. […] password (edit the kernel by adding 1 or "single" word in at the end) like this link: (…-linux-centos/), so this problem appears: (Error 11: unrecognized device string). I think that the Grub.conf file […]

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