Openstack nova Instance failed to push static IP through config drive. openstack/content/0000 is missing

So I need to bootstrap an instance that is configured as static IP through config drive, instead of the generic DHCP.  So with nova boot, everything seems to be happy but the instance just failed to get the static IP for some reason. Doing a nova console-log, the IP address shows like this in cloud-init.

cloud-init[775]: Cloud-init v. 0.7.5 running 'init' at Fri, 11 Sep 2015 17:56:46 +0000. Up 29.44 seconds.
cloud-init[775]: ci-info: +++++++++++++++++++++++Net device info+++++++++++++++++++++++
cloud-init[775]: ci-info: +--------+------+-----------+-----------+-------------------+
cloud-init[775]: ci-info: | Device |  Up  |  Address  |    Mask   |     Hw-Address    |
cloud-init[775]: ci-info: +--------+------+-----------+-----------+-------------------+
cloud-init[775]: ci-info: |  lo:   | True | 127.0.0.1 | 255.0.0.0 |         .         |
cloud-init[775]: ci-info: | eth0:  | True |     .     |     .     | fa:16:3e:4d:35:34 |
cloud-init[775]: ci-info: +--------+------+-----------+-----------+-------------------+

Obviously the eth0 is not getting the static IP. Once again I mounted the config-drive and then try to find the /openstack/content/0000 file but I can't find it.

[root@nova ~]# find /mnt/openstack | grep content
[root@nova ~]#

This is pretty weird as I remember the file should be there to allow static ip assignment to work through config-drive. So taking further looks, it seems the problem go to the subnet configuration. The subnet that the instance is on is having "enable_dhcp" equal to true, and that prohibited the config-drive to create the openstack/content/0000 file.

To disable DHCP for a subnet, run this.

# neutron  subnet-update  $SUBNET_UUID --enable-dhcp=False

Openstack broken metadata interfaces template

Was my 2nd time hitting the same issue and it wasted my whole day so I think I should document this as a note just in case it happens again.

In case you are seeing something like this from your metadata (be it metadata server, or config-drive), in this example I mounted the config drive as /mnt.

# cat /mnt/openstack/content/0000
DEVICE="{{ name }}"
NM_CONTROLLED="no"
ONBOOT=yes
TYPE=Ethernet
BOOTPROTO=static
IPADDR={{ address }}
NETMASK={{ netmask }}
BROADCAST={{ broadcast }}
GATEWAY={{ gateway }}
DNS1={{ dns }}

#if $use_ipv6
IPV6INIT=yes
IPV6ADDR={{ address_v6 }}
#end if

Chances that you are hitting this bug.

As cloud-init doesnt really recognize format like that, to fix the issue you will need to update the template /usr/share/nova/interfaces.template (assuming you are on CentOS/RHEL7) with something like this which is a debian-ish template

# Injected by Nova on instance boot
#
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
{% for ifc in interfaces -%}
auto {{ ifc.name }}
iface {{ ifc.name }} inet static
address {{ ifc.address }}
netmask {{ ifc.netmask }}
broadcast {{ ifc.broadcast }}
{%- if ifc.gateway %}
gateway {{ ifc.gateway }}
{%- endif %}
{%- if ifc.dns %}
dns-nameservers {{ ifc.dns }}
{%- endif %}
{% if use_ipv6 -%}
iface {{ ifc.name }} inet6 static
address {{ ifc.address_v6 }}
netmask {{ ifc.netmask_v6 }}
{%- if ifc.gateway_v6 %}
gateway {{ ifc.gateway_v6 }}
{%- endif %}
{%- endif %}
{%- endfor %}