Bug 1336952

Description of problem:
Overcloud nodes lose a custom domain name on reboot.

Version-Release number of selected component (if applicable):
OSP 8

How reproducible:
Create a yaml environment file containing:
parameter_defaults:
  CloudDomain: thedomain

Deploy the overcloud including the environment file in the "openstack overcloud deploy" command using -e.

ssh onto an overcloud node and "cat /etc/hostname".  Note that the file contains ".localdomain" as the domain name and not the one specified.

Reboot the node and note that the custom domain name is lost.

Steps to Reproduce:
1. See above.

Actual results:
Custom domain name is lost on reboot.

Expected results:
Custom domain name should be retained on reboot.

Additional info:
The following is from an email conversation with Steve Hardy:

*However* I noticed this isn't set correctly:
$ cat /etc/hostname
overcloud-controller-0.localdomain

Also these settings don't appear to survive a reboot, I rebooted the controller, then I see:

$ hostname -f
localhost
[heat-admin@overcloud-controller-0 ~]$ hostname overcloud-controller-0.localdomain

[heat-admin@overcloud-controller-0 ~]$ cat /etc/hostname overcloud-controller-0.localdomain

Here we can see why:

[root@overcloud-controller-0 ~]# journalctl  | grep hostname | grep CLOUDINIT | grep hostnamectl May 13 09:27:56 overcloud-controller-0 cloud-init[1086]: [CLOUDINIT]
util.py[DEBUG]: Running command ['hostnamectl', 'set-hostname', 'overcloud-controller-0.localdomain'] with allowed return codes [0] (shell=False, capture=True) May 13 09:58:42 overcloud-controller-0.localdomain cloud-init[1119]:
[CLOUDINIT] util.py[DEBUG]: Running command ['hostnamectl', 'set-hostname', 'overcloud-controller-0.localdomain'] with allowed return codes [0] (shell=False, capture=True)

And this is the code that does it:
http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/view/head:/cloudinit/sources/__init__.py#L195

Which gets its data from nova:
[heat-admin@overcloud-controller-0 ~]$ curl http://169.254.169.254/latest/meta-data/local-hostname
overcloud-controller-0

As we can see from the cloud-init code, it defaults to "localdomain"
because local-hostname isn't a fqdn.

#### Solutions ####

So.  At this point we have two options:

1 - Get local-hostname metadata to reflect the metadata we want

This is done by setting the dhcp_domain in nova.conf (not neutron as mentioned above).  I set it then restarted the nova services, then re-deployed and everything (including /etc/hostname) is set correctly and persists over reboot.

2 - Stop cloud-init messing with the hostnames and make the initial setting persistent

Clearly we ideally want to stop cloud-init messing with the correct CloudDomain derived hostname, so that we can allow operators to specify a domain via CloudDomain and have things just work.

I'm looking at the cleanest ways to do this, but the basic steps will be to correctly persist the CloudDomain derived fqdn on deployment, and disable the cloud-init update_hostnames module so it survives reboot, exact implementation tbc.

I raised this upstream bug so we can track (2):

https://bugs.launchpad.net/tripleo/+bug/1581472