Wider feedback requested on two changes to our base/core defaults

Lennart Poettering mzerqung at 0pointer.de
Mon Sep 9 19:30:01 UTC 2013


On Wed, 21.08.13 18:45, J├│hann B. Gu├░mundsson (johannbg at gmail.com) wrote:

> And I have come across a bit of scalability issue due to us
> defaulting to using short hostnames in login and command prompt when
> creating OS containers in any real numbers.

I am pretty sure we should continue to default to "short" hostnames,
i.e. not fqdns.

The thing is simply that in today's world hosts might appear on multiple
networks and domains at the same time, and that dynamically, and not
necessarily using IP or exposed via DNS. The domain suffix hence is
frequently something that is more interface or state dependent rather
than strictly host dependent. For example, the same host might have an
mdns hostname in .local as well as one ISP assigned hostname on ppp0 and
a hand chosen name on the LAN interface eth0. They might all share the
same non-qualified name, but are hightly like to have different
suffixes. Extending on that: sometimes a machine might be entirely
disconnected, an fqdn then makes very little sense, because it suggests
a world-wide reachable name which is misleading.

Enforcing a fixed fqdn for a a machine for its entire lifetime is
like enforcing a single fixed IP address for it -- i.e. a setup that
certainly makes sense but is probably not the common case for the vast
majority of modern systems.

Also, the hostname of the system is not only used for IP purposes. For
example bluetooth uses it too, and the shell displays it and whatnot.

In systemd's hostname support (as exposed via /etc/hostname, hostnamed,
hostnamectl, ...) we hence generally prefer non-fqdn names, however do
accept fqdns too. Server centric software like IPA requires FQDNs
though (which I personally think is a poor choice, but whatever...)

If an ISP wants to set up multiple containers he should probably make
sure on his own that the hostnames are unique on the container host, he
can manually choose fqdns for that, or even use his own scheme, for
example "customer23-host47" or whatever works for him... 

We try to find good defaults that work for everybody, not just specific
ISP setups. ISP setups tend to be fairly static, and hence
simple. However, static setups are generally just a boring special case
of dynamic setups, hence we generally implement things to cover that
well...

Lennart

-- 
Lennart Poettering - Red Hat, Inc.


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