Comment # 15 on bug 929471 from Dennis Golden

(In reply to Dr. Werner Fink from comment #13)
> Could it be that here the DNS/FQDN (Fully Qualified Domain Name) is mixed
> with the static hostname which is given in /proc/sys/kernel/hostname?
> 
> The first is bind normally to the first (ether)net device whereas the second
> is set by systemd-hostnamed.service(8) (compare with man:hostnamectl(1) and
> hostname(7)).  In common practice the names before the very first dot do
> agree but this is not required. Beside this there also exist YP/NIS domain
> names which may or may not agree with the DSN domain name.
> 
>        hostname - show or set the system's host name
>        domainname - show or set the system's NIS/YP domain name
>        dnsdomainname - show the system's DNS domain name
>        nodename - show or set the system's DECnet node name
> 
> For any MTA the Fully Qualified Domain Name of the host is the one which
> (IMHO) should be used as e.g. relay hosts/servers do check for this name.

The value in /proc/sys/kernel/hostname is set by the hostname command of which
is contained within the /etc/hostname file.

Regards,

Dennis