[et-mgmt-tools] Service discovery for cobbler and koan with Avahi

[Michael DeHaan]

Peter Wright wrote:
> David Lutterkort wrote:
>>
>> On Fri, 2007-08-17 at 13:53 -0400, Michael DeHaan wrote:
>> > How does this work?
>> >
>> >     Cobblerd will detect the presence of avahi-tools when it starts 
>> up,
>> > and will publish the service.
>> >
>> >     With koan, we specify --server=DISCOVER to tell koan it needs to
>> > probe for a cobbler server.
>> >
>> > For instance, the following command works regardless of where you are:
>> >   >     koan --server=DISCOVER --list-profiles
>>
>> Cool .. how about the following behavior: when koan is started without
>> --server, it first tries to look up a host named 'cobbler' and uses that
>> as the cobblerd; if no such host exists, try to discover using avahi; if
>> that fails tell the user they are dumb and need to give na explicit
>> server with --server ?
>>
> please do not put any hard coded hostnames in the koan code base.  two 
> immediate problems crop to mind:
>
> 1) a host named cobbler already exists and does not run cobblerd
> 2) the system becomes coupled to a working DNS system
>
>
> -p
>
>
>


Peter,

I'm not so sure I agree a few defaults is a bad thing, since it's pretty 
easy to test for cobblerd's presence (xmlrpc responding to certain 
method on certain port) and we wouldn't have to engage this check unless 
--server was omitted.  David's suggestion actually works pretty well to 
help out those running EL4 boot servers (where there is no Avahi) -- 
which is probably the most likely platform for a boot server at this 
point.    Rest assured I have ruled out "nmap" as a discovery method :) 

And obviously if  we specify --server (as was mandatory before) we can 
skip all of those checks (so you don't need DNS in that case). 

--Michael