Re: hostname-mode=default and hostname set outside NM

[Thomas HUMMEL <thomas hummel pasteur fr>]

On 4/27/20 5:34 PM, Thomas HUMMEL wrote:
> On 4/27/20 5:20 PM, Beniamino Galvani wrote:
>
> > It uses systemd-hostnamed, and falls back to gethostname() in case of
> > failure [1].
> I should then try to remove hostnamed just to figure out why in
>
> 1) hostname from initrd : fqdn
> 2) NM starts : hostname-originial == fqdn
> 3) dhcp : short name
> 4) an external tool issues hostname <short name> and creates another 
> higher priority NM profile
>
> NM (hostname-mode=default) restores the fqdn (as seen in traces) instead 
> of the short one in 3) which, according to what you just explained is 
> the LAST externally set.
>
> I'll try to figure out this myself...Thanks for your help.

Well, I was thinking about 4) :

hostname(1) says that hostname is set via sethostname(2). This is 
outside of NetworkManager but as it may also be outside 
systemd-hostnamed (hostname(1) was used and not hostnamectl or 
dbus-send) could that explain what I see ?

hostname(1) change the transient/kernel hostname but as 
systemd-hostnamed does not poll /proc/sys/kernel/hostname (which was 
confirmed to my in the systemd-devel list) for a change, this out-of-NM 
set hostname is not seen by NM, which then restores the last outside one 
seen BY himself, which is the hostname-original read from dbus at its 
start ?

Thanks

--
TH