On Mon, 18 Sep 2006, Jeff Vian wrote:
[...]
The hosts file predated DNS. As the internet grew a local file became
impossible to maintain and DNS grew from it.
DNS cannot have localhost defined since that is a generic name. Every
host has it defined and the IP is not routeable so it belongs in the
hosts file on every host. It has to be accessible even when the host is
not connected to the internet and/or has no DNS available.
[...]
Only _one_ name goes in /etc/sysconfig/network and that is the real nave
of the local host in FQDN format.
HOSTNAME=myhost.mydomain.com
is the format there.
[...]
Why localhost is required is simple enough.
Several things (including the X server) require access to network
protocols and require localhost to map to an address that works in order
to start up and run properly.
It isn't hardcoded because the address can be mapped differently if you
chose.
Thanks for a very clear explanation. One or two last questions I have
from following this discussion:
Is there any real harm in having other names associated with the loopback
address in /etc/hosts as well?
Is there any issue if the real HOSTNAME is associated with some other
nonroutable address in /etc/hosts if (a) the machine is not connected to a
network or (b) if it is connected to a network but has some other IP
(possibly routable) address on that network--either where other machines
on the network know the machine name and IP (from DNS, e.g.) or where they
don't?
Thanks.
--
Matthew Saltzman
Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs
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