On 2026-09-30 15:22, Chris Green wrote:
Thomas Pircher <[email protected]> wrote:
What does not work exactly?
chris$ ypdomainname
chris$ domainname
chris$ dnsdomainname
ypdomainname and domainname relate to NIS, as Greg already pointed out.
This is not related to the DNS domain name.
The dnsdomainname and hostname --fqdn commands will give you a more
useful answer, given you r configuration.
Is there a reason you use 127.0.1.1 instead of the more commonly used
value 127.0.0.1?
It's what a Debian 13 installation produces, I have 127.0.0.1 as
localhost (see above).
Yes, ignore what I wrote here. I was about 20 years out of date with my
comment.
However things like postfix and others use ypdomainname/domainname to
get the domain.
Postfix's documentation says it uses the fully-qualified domain name
from gethostname(2). This is slightly confusing, as I would expect that
to return just the hostname. If it wanted the DNS domain name, it would
have to resolve it using e.g. getaddrinfo(3).
This all sounds very brittle to me. Please consider setting `mydomain`
or `myhostname` in the Postfix configuration explicitly. You want to be
in control of this information, if your mail server is public facing.
Also see the discussion in "THE FQDN" in the man page of hostname(2): a
given machine can have zero, one or more domain names.
Thomas
