Re: Debian and FQDN lookup

[Alex Mestiashvili <alex@biotec.tu-dresden.de>]

On 04/02/2015 02:10 PM, Mihamina Rakotomandimby wrote:

Hi al,

WHen issuing 'hostname --fqdn', I'm supposed to get the FQDN.
Anyway when trying some different combinations, involving /etc/hostname, /etc/domainname, /etc/hosts, /etc/resolv.conf, I cannot figure out where the FQDN is looked up AND with what precedence.
Would you know the mechanism (precedence) and worlkflow where a Debian 7 machine gets its FQDN?

Thank you.

Hi,

the mechanism is described here:

 http://sources.debian.net/src/hostname/3.15/hostname.c/

and as far as I see it simply asks the DNS about the hostname using getaddrinfo.

On my system the "--fqdn" flag doesn't work if my /etc/resolv.conf doesn't have domain <mydomain> or search <mydomain> option enabled.

You can see it with strace hostname --fqdn.

Also see man resolver for additional information.

Alex