[CentOS] suddenly X gives black screen with small clock cursor

On Thu, Oct 10, 2013 at 08:08:08PM -0400, Fred Smith wrote:
> Gang:
> 
> I'm puzzled...
> 
> I rebooted a while ago (and in between the down and up, I installed Fedora
> 20 Beta on a USB hard drive, making sure it wouldn't mess with my Centos
> system). The install went fine, but afterwards, when I reboot Centos, it
> comes up with a black screen and a clock as the mouse cursor (small clock).
> 
> Tried CTRL-ALT-BKSP and the clock disappears and reappears.
> 
> I did "init 3" to stop the apparently busted X server, removed the X lock
> file from /tmp and attempted "startx", which didn't work either.
> when startx is run I get a bunch of messages ending with:
> 
> 	Initializing built-in extension XFree86-VidModeExtension
> 	Initializing built-in extension XFree86-DGA
> 	Initializing built-in extension XFree86-DRI
> 	Initializing built-in extension DRI2
> 	Loading extension GLX
> 	Loading extension NV-GLX
> 	Loading extension NV-CONTROL
> 	Loading extension XINERAMA
> 	xinit:  Permission denied (errno 13):  cannot open /dev/null: Permission denied
> 
> 	waiting for X server to shut down Server terminated successfully (0). Closing log file.
> 
> curiously, when I log in on a console I also get this:
> 
> 	-bash: /dev/null: Permission denied
> 	-bash: /dev/null: Permission denied
> 	-bash: /dev/null: Permission denied
> 	-bash: /dev/null: Permission denied
> 	-bash: /dev/null: Permission denied
> 	-bash: /dev/null: Permission denied
> 
> So something is seriously hosed here. Can anyone give me a clue?
> 
> thanks!

So, I don't know what the heck  happened, but I have what looks like a
solution: a number of important files in /dev somehow had their permissions
changed. I had to do the following:

	chmod a+rw /dev/null
	chmod a+rw /dev/urandom
	chmod a+rw /dev/zero
	chmod a+rw /dev/full
	chmod a+rw /dev/random

After which X started and the complaints about /dev/null went away.
As I worked thru fixing first /dev/null, each step got me a bit further,
with more complaints about inaccessable /dev/ entries, so I just kept
fixing them until the complaints went away. 

I also compared permissions in /dev against my Fedora 19 netbook, which is
how I knew what permissions to use for the rest, as well as being where I
found correct permissions, as well as /dev/zero and /dev/full being wrong.

I have NO CLUE what hosed the permissions, and I can't be sure that there 
may not be some other items also wrong (that I can't see because they
don't appear on the F19 system).

Can anyone suggest an accurate way to have the system fix all the permissions
in /dev? some arcane options on rpm, perhaps?

thanks!

Fred
> 
> -- 
> ---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
>                          God made him who had no sin
>                       to be sin for us, so that in him
>                  we might become the righteousness of God."
> --------------------------- Corinthians 5:21 ---------------------------------

-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
                    The Lord detests the way of the wicked 
                  but he loves those who pursue righteousness.
----------------------------- Proverbs 15:9 (niv) -----------------------------