Re: FQDNs for netbooted hosts via DHCP?

[Roy Marples <roy%marples.name@localhost>]

On 15/07/2018 03:37, Robert Elz wrote:
> As with most client/server systems, there are two separate things that need
> to be made to work - the server has to send the data that you want it to
> send (which might mean altering what the client requests, or server config,
> or ...) and then the client needs to "do the right thing" with the data that is
> returned.
>
> Lastly, for this, I wonder if perhaps that final "false" in need_hostname
> (in dhcpcd-hooks/30-hostname) might instead be something more like
>
> 	${hfqdn} && [  "${hostname}" = "${hostname#*.}" ]

If we're going to test that, then we need to check the converse for 
${hsort} && [ "$hostname" = "${hostname%%.*}" ]

The actual change required is a bit more invasive than that line change 
though, but it suffices for this discussion.

> so that (If I got that correct) if we want a FQDN as the hostname, and
> what has been set (by something else) is not a FQDN but just a short
> name, then we allow dhcpcd to set the FQDN (overriding whatever was
> set before).   If it had been this way, the force_hostname stuff would not
> have been needed.
>
> If that change is mde though it would  need to be made clear that
> (as the default is to set a FQDN) that simply setting a short hostname
> in rc.conf would not be effective, dhcpcd.conf would also need to be
> modified to allow short names if the DHCP server returns names.

The only other concern I have with this is that if we have two 
interfaces and dhcpcd receives the same short hostname on both but only 
a domain on one of them, then the hostname will flip-flop between short 
and long hostnames.

This is probably unlikely, but is worth pointing out.

> Roy: I'd also suggest getting rid of the '-a' operator in test arg lists,
> while it is probably OK in all systems as used, it is not really
> safe - test with more than 4 args (not counting the ']' when present)
> produces unspecified results.  Use && instead.   There are two of
> them in that script (well, the same one, more or less, in
> need_hostname() and set_hostname())

You're referring to this?
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html

>4 arguments:
    The results are unspecified.

Well, Today I Learned something new I guess.
I suppose my only concern is speed ... that would not produce any more 
subshells on NetBSD or any modern shell would it? Guess I should do some 
testing around that.

Roy