wireless connection and X session

[François Patte]

Rick Stevens a écrit :
> On Tue, 2006-05-02 at 15:17 -0500, Aaron Konstam wrote:
> 
>>On Tue, 2006-05-02 at 17:32 +0200, François Patte wrote:
>>
>>>Mikkel L. Ellertson a écrit :
>>>
>>>>François Patte wrote:
>>>>
>>>>
>>>>>Bonjour,
>>>>>
>>>>>I am facing a problem that I don't understand. I installed FC4 on my
>>>>>laptop and wireless is working fine but if I launch the wireless
>>>>>connection after the boot (using for instance ifup eth1) I loose the
>>>>>ownership of the X session, ie I am unable to open any graphical
>>>>>application.
>>>>>
>>>>>If I kill my session and log again, I recover this ownership (and the
>>>>>wireless connection is not lost...).
>>>>>
>>>>>Who can help me?
>>>>>
>>>>>Thank you.
>>>>
>>>>Dumb question - is your hostname changing when you bring up the
>>>>network connection? If so, this will cause problems in X.
>>>
>>>This seems to be exactly the problem and it seems to be present only
>>>with gnome..... (not appears with kde...)
> 
> 
> I don't buy that.  KDE may restart X when the hostname changes, but X
> depends on the hostname being set.  Read on.
> 
> 
>>>What can i do? How to guess the hostname you will get when you want to
>>>use a wifi in an airport for instance? Shall I put all possible names in
>>>/etc/hosts?
>>>
>>>I'm interrested to the solution of this problem....
>>>
>>>Thanks.
>>
>>Well here is my question. If you are using  wireless communication
>>using DHCP to multiple access points why are you defining a hostname?
>>Take the hostname the dhcp server gives you.
> 
> 
> That will only work if X comes up AFTER the machine receives its IP and
> hostname from the DHCP server.  Remember that the local X session is
> tied to the X server with its display at "hostname:0".  If the hostname
> changes to "newhostname" and you DON'T restart X, there'll be no
> "newhostname:0" display and you won't be able to open any new X clients.
> End of story.
> 
> If you're not sure if you'll get DHCPd before or after X comes up, the
> best bet is to define a fixed hostname and tie it to 127.0.0.1 in
> your /etc/hosts file (you already have one..."localhost") and ignore any
> hostname the DHCP server gives you.

this only works if you define the hostname in /etc/sysconfig/network

>  Edit your dhclient.conf file and
> add 'supersede host-name "localhost"' to the stanza that defines your
> connection.  For example (stripped down to minimums),
> 
>        timeout 60;
>        retry 60;
>        reboot 10;
>        select-timeout 5;
>        initial-interval 2;
> 
>        interface "wlan0" {
>            supersede host-name "localhost";  <<<---NOTE! Ignore DHCP
>            request subnet-mask, broadcast-address, time-offset, routers,
>                 domain-name-servers;
>            require subnet-mask, domain-name-servers;
>        }

This seems to be the best solution.

Thank you.

> 
> Alternately, you can accept the hostname the DHCP server gives you and
> then add some commands to /usr/sbin/dhclient-script (e.g.
> "/usr/sbin/gdm-restart") so X restarts with the new hostname.  I leave
> that as an exercise for the reader.

Hum!? there is no difference with: closing your session after setting up 
the network, then log in again. And it is quite violent!

-- 
François Patte
UFR de mathématiques et informatique
Université René Descartes
http://www.math-info.univ-paris5.fr/~patte