[Bug 1413388] Re: [SRU] upgrade of MAAS removes local config for bind and breaks DNS

[Andres Rodriguez]

** Description changed:

  On an Ubuntu 14.04 host, I recently upgraded MAAS from
  1.5.2+bzr2282-0ubuntu0.2 to 1.5.4+bzr2294-0ubuntu1.2.  This is a
  production environment which uses MAAS to control both DNS and DHCP.
  
  During the upgrade MAAS silently (without prompting) rewrote
  /etc/bind/named.conf.options.  However, in the process, it dropped
  some of our local config and broke DNS resolution for all clients in
  this environment.  Specifically, it removed and did not re-add a
  forwarders entry.
  
  I've attached 3 files: the original named.conf.options, the version
  left after the MAAS upgrade and an artifical diff between the two to
  show what's actually changed (i.e. ignoring MAAS rearranging things,
  messing up whitespace and removing comments).
+ 
+ 
+ [Impact]
+ In 1.7+, MAAS started managing DNS forwarders as part of its DNS management feature. However, if a user in 1.5 would manually modify their configuration file to add forwaders, after an upgrade to 1.7+, DNS would en up broken. This adds the ability for MAAS to upgrade the DNS configuration correctly and migrate the manually configuration to the MAAS managed configuration. 
+ 
+ [Test Case]
+ 
+ Without the fix:
+ 1. Install maas 1.5
+ 2. Configure MAAS to manage DNS/DHCP
+ 3. Manually edit /etc/bind/named.conf.options and add forwaders, allow-cache, allow-recursion and allow-cache-query options.
+ 4. Upgrade to MAAS 1.7 with proposed fix.
+ 5. MAAS will migrate the DNS forwarders config into MAAS' DB.
+ 6. MAAS won't write allow-cache, allow-recursion, allow-cache-query.
+ 
+ 
+ [Regression Potential]
+ Minimal. This has been tested extensively in various environments, both on fresh installs and upgrades.

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https://bugs.launchpad.net/bugs/1413388

Title:
  [SRU] upgrade of MAAS removes local config for bind and breaks DNS

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