[Bug 871966] Re: FQDN written to /etc/hosts causes problems for clustering systems

[Clint Byrum]

After discussing with Scott Moser, its agreed that this may cause
issues, but not necessarily that it is a "bug" as much as a change in
behavior that needs documenting. Adding a ubuntu-release-notes task with
suggested release note.

** Changed in: cassandra (juju Charms Collection)
       Status: New => In Progress

** Changed in: cassandra (juju Charms Collection)
     Assignee: (unassigned) => James Page (james-page)

** Changed in: cloud-init (Ubuntu)
   Importance: Undecided => Low

** Also affects: ubuntu-release-notes
   Importance: Undecided
       Status: New

** Description changed:

- By writing the FQDN to /etc/hosts as resolving to 127.0.1.1, systems
- like Cassandra have a much harder time determining their address to
- communicate to other cluster members.
+ *** Ubuntu 11.10 Release Note ***
+ 
+ Cloud instances and servers pre-seeded with cloud-init will have their
+ FQDN written to /etc/hosts and pointed to the IP 127.0.1.1. This may
+ cause issues for daemons which try to listen on their hostname, rather
+ than 0.0.0.0, as they will now only be reachable locally, rather than on
+ the network address that their FQDN resolves to.
+ 
+ ***
+ 
+ 
+ By writing the FQDN to /etc/hosts as resolving to 127.0.1.1, systems like Cassandra have a much harder time determining their address to communicate to other cluster members.
  
  While some might see communicating your IP to others as  a bug, being
  able to use gethostname() and then resolving it to get the actual IP
  address of one's machine is fairly important.
  
  Its my understanding that in resolving bug #802637 , the Debian
  networking docs were used as a guide:
  
  http://www.debian.org/doc/manuals/debian-reference/ch05.en.html
  Point 5.1.2 specifically.
  
  It does suggest that one needs an FQDN in /etc/hosts.
  
  However cloud-init should only set the addresss if it cannot be
  determined.
  
  cloud-init should first try gethostbyname() on the FQDN. If it resolves,
  *do not write FQDN to /etc/hosts*. This assures that if it has been
  configured to be resolvable by some method in nsswitch.conf such as DNS
  or NIS or etc., it will not be overidden by /etc/hosts.

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https://bugs.launchpad.net/bugs/871966

Title:
  FQDN written to /etc/hosts causes problems for clustering systems

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