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Make managing hosts entries optional

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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
This commit is contained in:
Jiri Stransky 2015-04-24 13:32:36 +02:00
parent c4072920ab
commit a43b23c45a
2 changed files with 25 additions and 2 deletions
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14
elements/base/README.rst
View File

@ -6,6 +6,20 @@ This is the base element.
Almost all users will want to include this in their disk image build,
as it includes a lot of useful functionality.
The `DIB_CLOUD_INIT_ETC_HOSTS` environment variable can be used to
customize cloud-init's management of `/etc/hosts`:
* If the variable is set to something, write that value as
cloud-init's manage_etc_hosts.
* If the variable is set to an empty string, don't create
manage_etc_hosts setting (cloud-init will use its default value).
* If the variable is not set, use "localhost" for now. Later, not
setting the variable will mean using cloud-init's default. (To
preserve diskimage-builder's current default behavior in the
future, set the variable to "localhost" explicitly.)
Notes:
* If you are getting warnings during the build about your locale

13
elements/base/install.d/10-cloud-init
View File

@ -9,6 +9,15 @@ set -o pipefail
# cloud-init May not actually be installed
mkdir -p /etc/cloud/cloud.cfg.d
dd of=/etc/cloud/cloud.cfg.d/10_etc_hosts.cfg << EOF
manage_etc_hosts: localhost
if [ ! -v DIB_CLOUD_INIT_ETC_HOSTS ]; then
echo "WARNING: In the future the default setting for manage_etc_hosts will not be overridden by this element."
echo "WARNING: Set DIB_CLOUD_INIT_ETC_HOSTS to 'localhost' to preserve current behavior."
fi
DIB_CLOUD_INIT_ETC_HOSTS=${DIB_CLOUD_INIT_ETC_HOSTS-localhost}
if [ -n "$DIB_CLOUD_INIT_ETC_HOSTS" ]; then
dd of=/etc/cloud/cloud.cfg.d/10_etc_hosts.cfg << EOF
manage_etc_hosts: $DIB_CLOUD_INIT_ETC_HOSTS
EOF
fi