Re: hostname-mode : short vs fqdn name

[Thomas HUMMEL <thomas hummel pasteur fr>]

On 4/9/20 10:59 AM, Beniamino Galvani wrote:
> > alking about D-Bus, I see this in the begining of all 3 (default, none,
> > dhcp) traces :
> >
> > Apr 08 14:53:29 maestro-1000.maestro.pasteur.fr NetworkManager[25235]:
> > <trace> [1586350409.2521] policy: get-hostname:
> > "maestro-1000.maestro.pasteur.fr" (from dbus)
> > Apr 08 14:53:29 maestro-1000.maestro.pasteur.fr NetworkManager[25235]:
> > <trace> [1586350409.2521] policy: hostname-original: set to
> > "maestro-1000.maestro.pasteur.fr"
> >
> > how is this hostname fully qualified who sets it ? The original hostname
> > always seems to be this one.
> I don't know, it is set before NM starts.

Hello, again

I tried to figure out the simplier case : hostname-mode=none.

I guess the above fqdn hostname read from D-Bus is the transient 
hostname, correct ? I don't think it can be set by dhcp if NM is the one 
which starts dhclient.

As a matter of fact, I saw that dhconfig() from dhcpd-scripts 
/usr/sbin/dhclient-script can indeed set the transient hostname.
The problem is that it sets the transient name only if hostname is 
needed, which, looking at the script is if transient hostname is empty 
or localhost :

need_hostname ()
{
    CHECK_HOSTNAME=$(hostnamectl --transient)
    if [[ "${CHECK_HOSTNAME}" = "(none)" ]] ||
       [[ "${CHECK_HOSTNAME}" = "localhost" ]] ||
       [[ "${CHECK_HOSTNAME}" = "localhost.localdomain" ]]; then
        return 0
    else
        return 1
    fi
}

which must not be the case because of the fqdn hostname we see BEFORE NM 
starts (I am assuming that dhclient is only started by NM of course here)...


Or could that initial fqdn hostname come from systemd-hostnamed at boot 
which would fall back setting the transient hostname by reverse dns 
lookup of the ip address ?

thanks
--
TH