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Re: where is /etc/hosts supposed to come from?

Vincent Lefevre <vincent@vinc17.org> writes:
> On 2009-12-30 11:54:57 -0800, Russ Allbery wrote:
>> Vincent Lefevre <vincent@vinc17.org> writes:

>>> "stanford.edu" is definitely wrong. First it's just a domain name, not a
>>> FQDN (as required by the mailname(5) man page).

>> stanford.edu is an RFC 1035 FQDN.

> RFC 1035 (from /usr/share/doc/RFC/links/rfc1035.txt.gz) doesn't define
> what a FQDN is. It doesn't contain "FQDN", and the only occurrence of
> "fully" and "qualified" is in "Gateways will also have host level
> pointers at their fully qualified addresses.

However, the other standards that do talk about FQDNs refer to RFC 1035
for the definition.  See, for instance, RFC 5322.

> FYI, here's what Wikipedia[*] (though not authoritative and sometimes
> containing errors) says:

>   For example, given a device with a local hostname myhost and a
>   parent domain name example.com, the fully qualified domain name is
>   written as myhost.example.com. This fully qualified domain name
>   therefore uniquely identifies the host — while there may be many
>   resources in the world called myhost, there is only one
>   myhost.example.com.

You're right, that's not authoritative and, in this case, is misleading.
Nothing about an FDQN implies uniqueness.  Wikipedia is trying to get at
the distinction between an unqualified name, which could duplicate many
other unqualified names in other domains, and a fully-qualified name which
has a single location in the DNS hierarchy.  However, an FQDN, despite
living in one place in the DNS hierarchy, may refer to multiple separate
systems (as it does for stanford.edu, time.stanford.edu, etc., all of
which are FQDNs).

Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

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