Attached patch has been tested and fixes the reported issue.
** Description changed:
+ [Impact]
+
+ * If bind9 is installed and configured as a local DNS server on an
+ ubuntu instance on GCE then on every reboot cloud-init will fail to
+ retrieve instance metadata from GCE due to the lookup hostname not
+ resolving.
+
+ * Backporting of this is necessary as instances with bind9 installed
+ can no longer take advantage of cloud-init
+
+ * The patch fixes this bug by updating the hostname used in the
+ metadata lookup to one that is included in /etc/hosts. As such it will
+ resolve, even if bind9 hasn't started yet.
+
+ [Test Case]
+
+ #launch an instance of ubuntu 14.04 on GCE
+ sudo apt-get update
+ sudo apt-get install -y bind9
+ #Add the Google DNS servers as global forwarders and configure bind9 for the
GCE environment
+ cat << EOF | sudo tee /etc/bind/named.conf.options
+ options {
+ directory "/var/cache/bind";
+
+ forwarders {
+ 169.254.169.254;
+ };
+
+ recursion yes;
+ dnssec-validation no;
+ dnssec-enable no;
+ auth-nxdomain no;
+ listen-on { 127.0.0.1; };
+ };
+ EOF
+ sudo service bind9 restart
+ #setup your instance to use bind9 instead of the Google server
+ echo "supersede domain-name-servers 127.0.0.1;" | sudo tee -a
/etc/dhcp/dhclient.conf
+ sudo dhclient -pf /run/dhclient.eth0.pid -x
+ sudo dhclient -1 -v -pf /run/dhclient.eth0.pid -lf
/var/lib/dhcp/dhclient.eth0.leases eth0
+ if grep -q "nameserver 127.0.0.1" "/etc/resolv.conf"; then echo "resolv.conf
has been updated"; fi
+ if host -t A metadata.google.internal | grep '169.254.169.254' > /dev/null;
then echo "host lookup succeeded as expected"; fi
+ sudo service bind9 stop
+ if host -t A metadata.google.internal | grep 'connection timed out' >
/dev/null; then echo "host lookup failed as expected"; fi
+
+ #Now reboot the instance
+ sudo reboot
+ #Once rebooted run the following
+ if grep -q "http://metadata.google.internal./computeMetadata/v1/ is not
resolvable" "/var/log/cloud-init.log"; then echo "cloud-init failed to lookup
metadata as expected"; else echo "cloud-init did _not_ fail to lookup metadata
as expected"; fi
+
+ A patched ubuntu14.04 has been built. To test the patch run the above but
after reboot run
+ #launch a patched instance
+ gcloud compute instances create ubuntu1404-patched-cloudinit --image
daily-ubuntu-proche-cloudinit-1404-trusty-v20160627 --image-project
ubuntu-os-cloud-devel
+
+ #on a patched instance run the following after reboot
+ if grep -q "http://metadata.google.internal/computeMetadata/v1/ is not
resolvable" "/var/log/cloud-init.log"; then echo "cloud-init failed to retrieve
metadata"; else echo "cloud-init did successfully retrieve metadata as
expected"; fi
+
+ [Regression Potential]
+
+ * GCE are questing this change.
+ * The reported issue only affects GCE users and only a small set of those
users will be using a local DNS server.
+ * The change is a single character change and has been tested and as such
has limited regression potential.
+
+
+ [Original Bug Report]
+
cloud-init hostname breaks because /etc/hosts does not have the trailing
dot on metadata FQDN.
Background:
On Ubuntu, cloud-init sets the hostname using our metadata service. To do
this, it hits "metadata.google.internal." (note trailing dot) via HTTP.
We have entries in /etc/hosts for the metadata service to ensure that we
can access it at boot time (if DNS is not yet up) as we have other init
scripts which block bootup when metadata cannot be reached. However,
these /etc/hosts entries only have "metadata.google.internal" (no
trailing dot) entries.
When a customer runs their own bind9 daemon, it starts *after* cloud-
init, meaning that cloud-init must use /etc/hosts to find the metadata
service. When it cannot, it incorrectly sets the hostname to
"$hostname.localdomain" instead of just $hostname.
Proposed fix:
Update:
http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/view/head:/cloudinit/sources/DataSourceGCE.py
Line 28 should read:
'metadata_url': 'http://metadata.google.internal/computeMetadata/v1/'
** Patch added: "lp-1581200-gce-metadatafqdn.debdiff"
https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/1581200/+attachment/4692729/+files/lp-1581200-gce-metadatafqdn.debdiff
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https://bugs.launchpad.net/bugs/1581200
Title:
Ubuntu cloud-init expects trailing dot on GCE metadata FQDN
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