Debian element should activate eth0

Cloud images expect the primary interface to run dhclient in order
to come up and acquire an IP address. Although we have technology
to manage without this for the undercloud and so on, the seed
still relies on this machinery in order to bring up its first
interface.

Change-Id: I079a679779de760ee9ca6f93cbb22e69a65e03af

elements/debian/root.d/08-debootstrap

@@ -54,6 +54,9 @@ else
         sudo sh -c "echo deb $DIB_DISTRIBUTION_MIRROR wheezy-backports main >> ${TARGET_ROOT}/etc/apt/sources.list"
         sudo chroot ${TARGET_ROOT} apt-get update
         sudo chroot ${TARGET_ROOT} apt-get install -y -t wheezy-backports $CLOUD_INIT_PACKAGES
+        cat << EOF | sudo tee -a ${TARGET_ROOT}/etc/network/interfaces
+source-directory /etc/interfaces.d
+EOF
     else # unstable
         sudo chroot ${TARGET_ROOT} apt-get install -y $CLOUD_INIT_PACKAGES
     fi
@@ -72,6 +75,14 @@ LABEL=cloudimg-rootfs / ext4 errors=remount-ro 0 1
     # specify a hostname so that cloud-init does not default to (None)
     sudo sh -c "echo 'hostname: debian' > ${TARGET_ROOT}/etc/cloud/cloud.cfg.d/01_hostname.cfg"
 
+    # cloud images expect eth0 to use dhcp.
+    sudo mkdir -p ${TARGET_ROOT}/etc/network/interfaces.d
+    cat << EOF | sudo tee ${TARGET_ROOT}/etc/network/interfaces.d/eth0
+# The primary network interface
+auto eth0
+iface eth0 inet dhcp
+EOF
+
     echo Caching debootstrap result in $DEBOOTSTRAP_TARBALL
     sudo tar -C $TARGET_ROOT -zcf $DEBOOTSTRAP_TARBALL .
 fi