Re: X session and hostname changing policy

[Dan Williams <dcbw redhat com>]

On Mon, 2010-06-14 at 23:16 +0300, Fırat Birlik wrote:
> Hi there,
> 
> I experience a problem with hostname manipulation of NetworkManager
> and the X session.  DHCP server sends a hostname within the dhcp
> offer, which is different the current one.  There is no persistent
> hostname definition within the 'nm-system-settings.conf' as this is a
> default installation.  NetworkManager just changes the hostname and as
> new hostname is not authenticated (xhost cookie MIT-MAGIC-COOKIE-1 for
> new hostname does not exist) no new application can be started
> afterwards.

The solution is *not* to use hostname for local X authentication at all.
Instead, you want to allow all connections via Unix sockets from the
session user, which means that your X init should be doing something
like this:

[ -x /usr/bin/xhost ] && [ -x /usr/bin/id ] &&
    xhost +si:localuser:`id -un` >& /dev/null

which normally goes in 'localuser.sh' in /etc/X11/xinit/xinitrc.d or
wherever scripts get executed during X init time.  Hostnames do change
and relying on it for something like local authentication will certainly
break stuff.

Most distros have had this fixed for a while now.

Dan

> To avoid this behavior, I can define a persistent hostname equal the
> content of /etc/HOSTNAME (this is a slackware system) as the
> following:
> 
> --- /etc/NetworkManager/nm-system-settings.conf~
> +++ /etc/NetworkManager/nm-system-settings.conf
> @@ -1,2 +1,5 @@
>  [main]
>  plugins=keyfile
> +
> +[keyfile]
> +hostname=myhostname
> 
> 
> As persistent hostname has highest precedence, problem looks solved;
> but this should be repeated for each installation.
> 
> What I'm asking is, is there any config option or some way to not let
> NetworkManager change the hostname?
> 
> As a note, current precedence order for hostname (taken from
> NetworkManagerPolicy.c):
> 
> 	 * 1) a configured hostname (from system-settings)
> 	 * 2) automatic hostname from the default device's config (DHCP, VPN, etc)
> 	 * 3) the original hostname when NM started
> 	 * 4) reverse-DNS of the best device's IPv4 address
> 
> 
> Thanks,
> 
> Firat
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