[et-mgmt-tools] "Could not communicate with" error

Michael DeHaan mdehaan at redhat.com
Wed May 30 18:13:07 UTC 2007

Bill McGonigle wrote:
> On May 30, 2007, at 10:43, Michael DeHaan wrote:
>> If this is a fresh install, most likely you haven't rebooted so 
>> cobblerd didn't come on automatically.
>> /sbin/service cobblerd start
>> Otherwise it might be a firewall issue, in which case you want to 
>> unblock TCP port 25151.
> Thanks, for the response, Michael. As I mentioned, cobblerd is 
> running, I can telnet to the port, and I tried turning off iptables.
> Thanks,
> -Bill
> -----
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My apologies on my reading comprehension. Judging from the system name, 
you've found a bug with system names not being something I ordinarily 
expect them to be. Thankfully, there is an easy workaround that will do 
what you want.

Explanation -- What's going on is Cobbler system objects ("cobbler 
system add --name=$name") really like to be IP's or hostnames, because 
these are things that bootloaders understand. PXE, for instance, can't 
key off of a hostname. In most places, if a hostname is given, cobbler 
internally maps it to it's resolved IP when setting up a PXE tree. This 
is really needless because it causes a bunch of dns lookups in an area 
of the code that shouldn't have to be doing this. So, best practices 
should state that cobbler system objects, as currently implemented, 
should be keyed off of MAC addresses, not hostnames. Now, this 
restriction really shouldn't apply to virt, so what we'll have 
eventually is allowing any value for --name and have a seperate 
parameter for specifying the --mac-address (and we already have 
--ip-address upstream). If --mac-address isn't specified, you'll still 
be able to create system objects, they just won't be PXE-able.

It would look something like this:

cobbler system add --name=this_is_just_a_description 
[--mac-address=AA:BB:CC:DD:EE:FF] [--ip-address=]

So, how to get around the above problem?

Unless you need system specific kickstart templating, you can install 
koan using profiles, and it's much simpler. You won't have to create 
cobbler system objects for the machines unless you want cobbler to 
manage your DHCP and/or DNS features for these systems -- and in which 
case, you should be creating a system object that is keyed off a MAC 

So, how to run koan with profiles?

koan --virt --profile=foo --server=bootserver.example.com 

You can also create regular cobbler system objects using a MAC address 
of your choice, and provision from that...

koan --virt --profile=foo --server=bootserver.example.com 

And that won't run into the bug where the hostname isn't looked up.

This will be straightened out more in the next release.

Thanks for pointing this out!


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