Julian,

So I made the directory to be owned by maas user, root group, and this is the outcome:

ubuntu@maas:/etc/bind$ ls -l maas/
total 12
-rw-r--r-- 1 root root  99 Aug 29 08:57 named.conf.maas
-rw-r--r-- 1 root root 193 Aug 29 08:57 named.conf.rndc.maas
-rw-r--r-- 1 root root 539 Aug 29 08:57 rndc.conf.maas
ubuntu@maas:/etc/bind$ sudo chown -R maas:root maas
ubuntu@maas:/etc/bind$ ls -l maas/                                                                                                            
total 12
-rw-r--r-- 1 maas maas  99 Aug 29 09:05 named.conf.maas
-rw-r--r-- 1 maas root 193 Aug 29 08:57 named.conf.rndc.maas
-rw-r--r-- 1 maas root 539 Aug 29 08:57 rndc.conf.maas

Now, I re-enabled  the DNS server from the WebUI , the following error was seen in the celery.log. Additionally, I noticed that permissions on named.conf.maas were changed, causing bind9 to fail reloading the configuration file:

== Incorrect file permissions ==
ubuntu@maas:/etc/bind$ ls -l maas/                                                                                                            
total 12
-rw------- 1 maas maas  99 Aug 29 09:05 named.conf.maas
-rw-r--r-- 1 maas root 193 Aug 29 08:57 named.conf.rndc.maas
-rw-r--r-- 1 maas root 539 Aug 29 08:57 rndc.conf.maas

=== bind failure (syslog) ===

Aug 29 09:05:33 maas named[23407]: received control channel command 'reload'
Aug 29 09:05:33 maas named[23407]: loading configuration from '/etc/bind/named.conf'
Aug 29 09:05:33 maas named[23407]: /etc/bind/named.conf.local:9: open: /etc/bind/maas/named.conf.maas: permission denied
Aug 29 09:05:33 maas named[23407]: reloading configuration failed: permission denied

=== celery error log ===

[2012-08-29 09:05:33,405: INFO/MainProcess] Got task from broker: provisioningserver.tasks.write_full_dns_config[3b7fe6ce-380f-442c-a9[67/784]
0e71313]
[2012-08-29 09:05:33,446: INFO/MainProcess] Got task from broker: provisioningserver.tasks.rndc_command[86c0d418-cb60-4720-b051-212b0f891782]
[2012-08-29 09:05:33,451: INFO/MainProcess] Task provisioningserver.tasks.write_full_dns_config[3b7fe6ce-380f-442c-a9fe-56fcd0e71313] succeede
d in 0.0323147773743s: None
[2012-08-29 09:05:33,498: ERROR/MainProcess] Task provisioningserver.tasks.rndc_command[86c0d418-cb60-4720-b051-212b0f891782] raised exception
: UnpickleableExceptionWrapper('subprocess', 'CalledProcessError', (), 'CalledProcessError()')
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/celery/execute/trace.py", line 47, in trace
    return cls(states.SUCCESS, retval=fun(*args, **kwargs))
  File "/usr/lib/python2.7/dist-packages/celery/app/task/__init__.py", line 247, in __call__
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/celery/app/__init__.py", line 175, in run
    return fun(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/tasks.py", line 165, in rndc_command
    execute_rndc_command(arguments)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/dns/config.py", line 110, in execute_rndc_command
    stdout=devnull)
  File "/usr/lib/python2.7/subprocess.py", line 511, in check_call
    raise CalledProcessError(retcode, cmd)
CalledProcessError: CalledProcessError()
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/celery/execute/trace.py", line 47, in trace
    return cls(states.SUCCESS, retval=fun(*args, **kwargs))
  File "/usr/lib/python2.7/dist-packages/celery/app/task/__init__.py", line 247, in __call__
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/celery/app/__init__.py", line 175, in run
    return fun(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/tasks.py", line 165, in rndc_command
    execute_rndc_command(arguments)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/dns/config.py", line 110, in execute_rndc_command
    stdout=devnull)
  File "/usr/lib/python2.7/subprocess.py", line 511, in check_call
    raise CalledProcessError(retcode, cmd)
CalledProcessError: CalledProcessError()