[aclug-L] Re: X server crashes Linux - why?

[John Goerzen <jgoerzen@xxxxxxxxxxxx>]

Well there are several issues at work here.

First of all, the X server takes control over the console (keyboard,
mouse, screen).  This means that if the X server has a problem, it can
APPEAR that the machine is locked, when in fact, it is not (you could
still telnet in to it, for instance).  You might try
Ctrl-LeftAlt-Backspace sometime if you think it has crashed; if it's
not too terribly badly wedged, this chould kill th eX server process.

The second reason is that the X server runs setuid root.  It has to do
this in order to take over the console and control the video card.
Note that the Framebuffer device in the kernel may alleviate this
problem in some cases.  Anyway, when it is running as root, all bets
are off as it can basically do anything.  Note that even though the
server runs as root part o fthe time, the apps that run in X do not.

-- John

John Reinke <jmreinke@xxxxxxxxx> writes:

> I am curious about WHY a crashing X server can crash Linux. Isn't it an
> application, and doesn't Linux have protected memory? All I know is that
> once every few weeks I'll be working on something (just a few consoles
> open, no Netscape) and then everything will lock up. I can't switch to a
> virtual console or connect to the machine so I assume the machine is
> crashed. Is this preventable, or is it a problem Linux users just deal
> with? Surely this isn't normal.
> 
> John
> 
> Michael A. Holmes wrote:
> >I have netscape installed on my computer, and about every third time it
> >crashes
> >and locks up the xwin server, then when you finally get it to reboot, as the
> >...
> 
> 
> 
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-- 
John Goerzen   Linux, Unix consulting & programming   jgoerzen@xxxxxxxxxxxx |
Developer, Debian GNU/Linux (Free powerful OS upgrade)       www.debian.org |
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