Host ID.

Robert Watson rwatson at
Sun Apr 8 10:19:02 UTC 2007

On Sun, 8 Apr 2007, Dag-Erling Smørgrav wrote:

> Pawel Jakub Dawidek <pjd at> writes:
>> If we move disks with root file system, it's this more or less the same 
>> host, isn't it?
> No.  I recently installed three servers by replicating the disk from a 
> fourth and changing the host name and IP address in rc.conf.

Yes, one of the nice properties of FreeBSD -- as opposed to, say, Windows, is 
that it's trivial to install a hundred boxes by dropping the same image onto 
all of them and configuring host-specific parameters using DHCP.  But there is 
a tricky tension here: the notion of a persisting host ID is very useful, in 
the a similar way to the way in which a persisting SSH host key is useful. 
If we're going to adopt a host ID model, we may want to make generation and 
configuration of the host ID conditional on an explicit variable in rc.conf 
(i.e., hostid_enable="YES" which causes it to be generated the first time and 
loaded future times, similar to SSH keys), and make it very easy to force a 
regen.  That way, you can image the boxes with the rc.conf setting set, but 
they don't generate host IDs until they boot the first time.

Robert N M Watson
Computer Laboratory
University of Cambridge

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