diff --git a/tools/build-image.sh b/tools/build-image.sh
index 71ac6d7e5b..d63f53e5e1 100755
--- a/tools/build-image.sh
+++ b/tools/build-image.sh
@@ -21,14 +21,25 @@
 
 set -e
 
-export ELEMENTS_PATH=${ELEMENTS_PATH:-nodepool/elements}
+## Other options
+# export DISTRO=${DISTRO:-centos-minimal}
+# export DISTRO=${DISTRO:-fedora-minimal}
 export DISTRO=${DISTRO:-ubuntu-minimal}
+
+## Overrite the release
+# export DIB_RELEASE=${DIB_RELEASE:-trusty}
+# export DIB_RELEASE=${DIB_RELEASE:-25} # fedora
+
+export ELEMENTS_PATH=${ELEMENTS_PATH:-nodepool/elements}
 export IMAGE_NAME=${IMAGE_NAME:-devstack-gate}
 export NODEPOOL_SCRIPTDIR=${NODEPOOL_SCRIPTDIR:-nodepool/scripts}
-export CONFIG_SOURCE=${CONFIG_SOURCE:-https://git.openstack.org/openstack-infra/system-config}
-export CONFIG_REF=${CONFIG_REF:-master}
 export EXTRA_ELEMENTS=${EXTRA_ELEMENTS:-}
 
+## Test your changes to system-config by overriding this; note you can
+## get a CONFIG_REF from gerrit should you have uploaded a change
+# export CONFIG_SOURCE=${CONFIG_SOURCE:-https://git.openstack.org/openstack-infra/system-config}
+# export CONFIG_REF=${CONFIG_REF:-refs/changes/12/123456/1
+
 ZUUL_USER_SSH_PUBLIC_KEY=${ZUUL_USER_SSH_PUBLIC_KEY:-$HOME/.ssh/id_rsa.pub}
 if [ ! -f ${ZUUL_USER_SSH_PUBLIC_KEY} ]; then
     echo "Error: There is no SSH public key at: ${ZUUL_USER_SSH_PUBLIC_KEY}"
@@ -36,6 +47,14 @@ if [ ! -f ${ZUUL_USER_SSH_PUBLIC_KEY} ]; then
     exit 1
 fi
 
+## If your firewall won't allow outbound DNS connections, you'll want
+## to set these to local resolvers
+# NODEPOOL_STATIC_NAMESERVER_V4=192.168.0.1
+# NODEPOOL_STATIC_NAMESERVER_V6=2000::...
+
+## This will get dib to drop you into a shell on error, useful for debugging
+# export break="after-error"
+
 # The list of elements here should match nodepool/nodepool.yaml
 disk-image-create -x --no-tmpfs -o $IMAGE_NAME \
     $DISTRO \