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

Fri Oct 11 18:06:19 UTC 2013
Fred Smith <fredex at fcshome.stoneham.ma.us>

On Fri, Oct 11, 2013 at 09:41:08AM -0400, Fred Smith wrote:
> On Fri, Oct 11, 2013 at 02:50:14AM -0700, John Doe wrote:
> > From: Fred Smith <fredex at fcshome.stoneham.ma.us>
> > 
> > >  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).
> > > 
> > >     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
> > > 
> > > Can anyone suggest an accurate way to have the system fix all the permissions
> > > in /dev? some arcane options on rpm, perhaps?
> > 
> > Nothing at all in the logs...?
> 
> Nothing I can see in the logs looks particularly damning.
> 
> > Global check: rpm -qVa
> running that right now, will post again if anything interesting turns up.
> 
> > Maybe check udev confs...?
> I was thinking of that, but the amount I know aobut udev wouldn't cover
> the head of a pin. Open to suggestions, though.

Looking in /lib/udev/rules.d/50-udev-default.rules I see:

KERNEL=="ptmx",			GROUP="tty", MODE="0666"
KERNEL=="null|zero|full|random|urandom", MODE="0666"

so if I understand them right, /dev/ptmx, /dev/null, /dev/zero, /dev/full,
/dev/random, and /dev/urandom should all come up as 'rw' for all users
after a system boot, but they don't. I reboot and they all come up as
0644, crw-rw----.  grepping for "null" in /lib/udev finds only that
single entry in all of the files, as does "ptmx".

So, I wonder if something is preventing this file from being run (which
seems unlikely, given that it contains a ton of rules which would all
be skipped). I note that /etc/udev/rules.d contains a rules file with
exactly the same name (which sets up some firewire stuff) and wonder if
that's a problem,... anyone know?

-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
   "For the word of God is living and active. Sharper than any double-edged 
   sword, it penetrates even to dividing soul and spirit, joints and marrow; 
              it judges the thoughts and attitudes of the heart."  
---------------------------- Hebrews 4:12 (niv) ------------------------------