Date: Sat, 31 Jul 2010 22:37:58 -0600 From: William Astle <l...@l-w.ca>
To: clug-talk@clug.ca Subject: Re: [clug-talk] how to boot without knowing any password Message-ID: <4c54fa26.70...@l-w.ca> Content-Type: text/plain; charset=us-ascii; format=flowed On 10-07-31 09:12 PM, clug-li...@vlietwerkz.ca wrote: Ubuntu and most of it's variants don't /use/ a root password though it can be set if you really want. The root password is not set by default for security reasons. The effect is that if an attacker attempts to log in as root, they will have no success no matter how many times they try because the root user is not /able/ to log in directly... The proper method for Ubuntu / Kubuntu / etc. is to log in as an admin enabled user - usally the user that was first set up - and use the command line as such: # sudo<whichever command/binary you want to use> password: The system will prompt you for the user's password. The password is hidden - in fact, no characters of any sort are displayed, so be careful typing the user's password. If they are set up as an admin and are also in the "sudoer" file, then the application will(should) execute as root. A neat little trick I use to keep from having to type sudo all the time is to run: # sudo su - It's a neat trick, but don't get in the habit of doing it all the time - it's bad muju. Or you could just use "sudo -i" which accomplishes the same thing. Of course, none of this helps if you can't log in in the first place because you don't know ANY password on the system. This is the case in the original query. All variants of UNIX, including Linux, have a "single user" mode which you can always get to provided you have access to the physical console of the machine. Single user mode is basically "init 1" with no GUI and minimal file systems mounted but enough to do necessary repairs as root to get your system running. You usually get to single user mode by interrupting the boot process and editing the boot string to append "single" to the kernel parameters and maybe adjust a few others. Ubuntu has dumbed down this process a little by adding a "recovery" item on the Grub boot menu. If you don't see a grub boot menu on startup, press esc after BIOS initialization and it should appear. The recovery boot starts a sub menu with one of the options being to go to a root shell. Select this option, then do the following commands: adduser <your userid> reboot The adduser command will prompt you for a password and some profile info . Upon reboot you should be able to enter the new id/password combo to get access to the system and keep the Ubuntu security model in place whereby you enter your own password to SUDO commands or system modification prompts rather than a real root password. I tested this successfully on Ubuntu 9.04. Ubuntu 10.4 uses an updated Grub which I haven't used for a while, but hopefully it still has the recovery boot option. If you google "Ubuntu lost password" you'll find other creative ways to get around this issue. Good luck! Greg
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