Dear Shu.
Thanks for that explanation.
Concerning RH or CentOS: I have to define /etc/hosts on all machines that do not obtain their hostname via DHCP. I have not yet figured out that the HOSTNAME variable in /etc/sysconfig/network is used in any form (correct me if I am wrong).
See /etc/rc.d/rc.sysinit. In that file you can find following lines
(snip)
if [ -f /etc/sysconfig/network ]; then . /etc/sysconfig/network fi
(snip)
# Set the hostname. update_boot_stage RChostname action $"Setting hostname ${HOSTNAME}: " hostname ${HOSTNAME}
(snip)
The ${HOSTNAME} variable comes form /etc/sysconfig/network.
I still wonder why it also works if hostname is only set in /etc/hosts like:
127.0.0.1 localhost 10.0.0.50 myserver.domain.example myserver
and $HOSTNAME is undefined.
Best Regards Marcus