Diskimage-builder currently writes cloud-init config file which adds a
host entry mapping the hostname and FQDN to 127.0.0.1 into every image
built. This is probably useful for some use cases but not for all, so we
now allow customizing the manage_etc_hosts value via
DIB_CLOUD_INIT_ETC_HOSTS variable and also not writing the config at all
if that variable is explicitly set to an empty string (currently the
default is 'localhost' but in the future the default will be empty
string).
Particular description of the problem this causes in TripleO follows:
We get hosts files like this:
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
127.0.0.1 ov-rl5i5saoc6h-1-hj5tzsbrdv4c-controller-dy6nuyarqy5z.novalocal ov-rl5i5saoc6h-1-hj5tzsbrdv4c-controller-dy6nuyarqy5z
# HEAT_HOSTS_START - Do not edit manually within this section!
192.0.2.17 ov-rl5i5saoc6h-0-wfzcsrqo34p6-controller-m3hy26lhxavl ov-rl5i5saoc6h-0-wfzcsrqo34p6-controller-m3hy26lhxavl.novalocal
192.0.2.15 ov-rl5i5saoc6h-1-hj5tzsbrdv4c-controller-dy6nuyarqy5z ov-rl5i5saoc6h-1-hj5tzsbrdv4c-controller-dy6nuyarqy5z.novalocal
192.0.2.16 ov-rl5i5saoc6h-2-a6v7saxnivm5-controller-7jboskte34r7 ov-rl5i5saoc6h-2-a6v7saxnivm5-controller-7jboskte34r7.novalocal
# HEAT_HOSTS_END
The duplicate hostname/FQDN entry for 127.0.0.1 and 192.0.2.15 confuses
Corosync, which then fails to start a cluster when using hostnames in
the config file instead of IPs.
Change-Id: Ia8582883f737548e2911d3f36a1943e5b236281b
Partial-Bug: #1447497
