systemd: please stop trying to take over the world :)

[Dan Williams]

On Tue, 2011-06-14 at 10:21 -0400, Simo Sorce wrote:
> On Tue, 2011-06-14 at 14:08 +0200, Lennart Poettering wrote:
> > On Tue, 14.06.11 07:25, Simo Sorce (simo at redhat.com) wrote:
> > 
> > > > > What's the problem of having a specific hostname set up at boot
> > > > time ?
> > > > 
> > > > The user might want to change it?
> > > 
> > > Does setting it at boot time prevent you from changing it later ?
> > 
> > No, systemd will initialize it at boot and is happy if you change it later.
> 
> As I thought, then I see no problem here.

systemd might be happy if you change it later, but other stuff is not.
The canonical example is X, where the hostname was used as the xauth key
to allow you to actually talk to the X server.  When the hostname
changed, there was no authorization for the new hostname in your xauth
file, so starting new apps would silently fail.  Basing *anything* like
that on your machine hostname is just stupid.  It might work for you,
but it doesn't work for lots of other people, so lets fix it for
everyone.  And we did back in the F10 timeframe
with /etc/X11/xinit/xinitrc.d/localuser.sh where we just let any local
user connect, since that's exactly what xauth's hostname thing was
supposed to do anyway.

The next example is apps that try to find out your IP address by looking
up your hostname.  That's completely broken too.  Do you have multiple
interfaces? Multiple IP addresses?  Are you behind NAT?  Yeah, all that
will torpedo hostname->IP lookups.  Hostnames are *informational* and
are never a good way to identify anything concrete on a local machine.
That didn't used to be the case, but now it is.  Things change in 40
years.

Dan