fai trick: fix weird hostname

[Holger Schurig]

Sometims I have to setup similar servers for customers. They don't end up 
in our local LAN, so they don't get local IP adresses. Instead, they get 
some short-lived dynamic IP address via DHCP.

There is no hostname in our local DNS for those DHCP addresses, so FAI 
assigns the IP address (!) to HOSTNAME. But '172.16.1.241' is a weird 
hostname. This is later used in /etc/hostname, /etc/hosts and probably at 
other places.


The following hook fixes this behavior:


/usr/local/fai/hooks/setup.DEFAULT.source

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echo $HOSTNAME | grep -q ^[0-9] && {
        export HOSTNAME=linux
        hostname $HOSTNAME
}
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