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Re: Debian and FQDN lookup


On Thu, 02 Apr 2015 14:54:19 +0200
Alex Mestiashvili <alex@biotec.tu-dresden.de> wrote:

> 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.

But, with stock nsswitch.conf, it issues uname(2) syscall first, goes
to /etc/hosts second, and if it encounters FQDN hostname - it all ends
If /etc/hosts contain only bare hostname - it'd return a bare hostname.

Only if /etc/hosts does not contain a hostname - a DNS search will be
performed (or other resolving method, all according to nsswitch.conf).

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

Or it's because you have a bare hostname in /etc/hosts ;)

> You can see it with strace hostname --fqdn.

All this invaluable information above was provided you by strace :)


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