schroot fails to resolve localhost in the absence of internet connection

[Chow Loong Jin]

  affects ubuntu/eglibc
  affects ubuntu/schroot

In the absence of an Internet connection, nothing in a spawned schroot seems to
be able to resolve localhost. Connecting to 127.0.0.1 fails too.

The reason for this is that NetworkManager adds the following entry to
/etc/hosts, if it was not already present:
::1 $HOSTNAME localhost6.localdomain6 localhost6

`getent hosts` then shows two 127.0.0.1 entries:-
127.0.0.1 localhost.localdomain localhost
127.0.0.1 $HOSTNAME localhost6.localdomain6 localhost6

And /etc/schroot/setup.d/20nssdatabases then dumps this output into the
schroot's /etc/hosts during the setup process.

I don't know why this even works when there's an internet connection, but having
multiple 127.0.0.1 entries in /etc/hosts is definitely malformed and should be
fixed.

There appears to be some discussion about getent and IPv6[1] which mentions that
"getent ipnodes" should be used instead, but ipnodes doesn't seem to be a
supported database by Ubuntu's getent:-

hyperair@ipwn:~% getent ipnodes localhost6 [10:34AM]
Unknown database: ipnodes

[1] http://<email address hidden>/msg11440.html

--
Kind regards,
Loong Jin