Suffering with a log in problems for user accounts but I have compounded it by accidentally disabling local log in!
Using CentOS 5 and from within the local root user I opened the log in screen preferences and then opened the Security tab. I then opened the "configer Xserver" and I have unchecked the "logins are handled by this computer". Now Since I have logged out of root all I have is the X cursor on a black screen and no log in. Obviously logins are not handled by this computer as I unchecked it!!!!!!!
Is there anyway to get this back on as I cannot access this from another PC.
Thanks

Do you happen to have access to a Live CD? Almost any distro should work... load your PC via Live CD, determine which configuration file needs to be changed... make the modification and reboot and you should be golden...

Unfortunately I dont have access to a live CD. I have worked out how to get a shell up and I can access the root account. Can I activate the GUI from within this shell??

Depends on how exactly you got that shell running. If you have a username (root or some user) you might be able to run `startx` and get a GUI, but don't hold your breath!

Some files of interest:

/etc/securetty # sets which tty's root can login on (at least "console" should be uncommented if root can login on local console.
/etc/login.access # sets who's disallowed to login from where.
/etc/nologin # if exists, will inhibit non-root logins.
/etc/login.defs # a bunch of configuration fields pertaining to logins in general.

If you can't get the GUI, have a look in those files for starters, and see if you can determine if they are configured such that local logins are not allowed. Keep track of what you change, in case you accidentally create a security hole!!!

Good luck.

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Why does this need a live CD?

There are two ways to attempt to get in. If you reboot the system and catch grub. Go to the default installation and edit it, go to the kernel line and place a 3 at the end (this setting is not saved). Alternatively try combinations of keys with the F3 button, example Alt + Ctrl + F3 until it drops you into a console.

This will declare run level 3 what will give you terminal/console access to the system. Unfortunately I do not know what file needs to be edited to fix this tho. If none of this works, you might be looking at having actually go into single user-mode to fix this... what is run level 1...

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I managed to get the shell up by usinf ctrl Alt F1. I was then able to log into the root user

I have managed to get the gui back up and running.
If I had read the error messages correctly when I attempted the startx command I would have seen the problem was a lock file in the tmp folder. removed it and xstart worked. I have now rechecked the logins handled by this computer box in the security tab and at least this problem is fixed. Now to deal with the network log in problems...........I may return soon.

Thanks for the input guys!!!

gah, i didn't even think to edit grub / init... thanks, that has given me a new tool.

No problem, I have to break into servers occasionally to reset passwords, at customers request of course. Ubuntu is different to CentOS on how to get a root terminal as such. Ubuntu gives single user mode as an option in grub by default but it's passworded. There are still ways passed this (ie init=/etc/bash on the kernel line).

With Centos and some other distros you can boot the install media and at the initial prompt, ignore the menu options and type

linux rescue

at the text prompt below. That will boot a RAMdisk version of Linux from the DVD/Cd and attempt to mount the HDD as a non-active disk under '/mnt'. You can then amend files on the HDD