Initial framework for starting k3d clusters.

+* Create a new repo, add this as a submodule(generally placed as
+  k3d-allocator).
+* Copy examples/k3d.env.sample to $repo/.k3d.env, configure BUILD_NAME,
+  add to .gitignore.
+* Copy examples/app-start-k3d.sh to $repo/start-k3d.sh, adjust
+  relative path to k3d-allocator/start-k3d.sh, add to git.
+* Copy examples/k3d.conf.sample to $repo/k3d.conf, adjust if needed,
+  add to git.

+#!/bin/sh
+
+APP_DIR="$(cd "$(dirname "$0")/."; pwd -P)"
+
+exec "$APP_DIR/k3d-allocator/start-k3d.sh" --app-dir "$APP_DIR" "$@"
+

+---
+apiVersion: k3d.io/v1alpha5
+kind: Simple
+metadata:
+  name: local
+ports:
+  - port: 80:80
+    nodeFilters:
+      - loadbalancer
+  - port: 443:443
+    nodeFilters:
+      - loadbalancer
+
+options:
+  k3s:
+    extraArgs:
+      - arg: "--disable=traefik"
+        nodeFilters:
+          - servers:*

+# Copy this to .k3d.env, adjust as needed
+
+BUILD_NAME=um-local-adam
+

+#!/bin/bash
+
+set -xe
+
+APP_DIR=""
+BUILD_NAME=""
+while [[ $# -gt 0 ]]; do
+	case "$1" in
+		(--app-dir)
+			APP_DIR="$2"
+			shift 2
+			;;
+		(--build-name)
+			BUILD_NAME="$2"
+			shift 2
+			;;
+		(*)
+			break
+	esac
+done
+
+if [[ -f $APP_DIR/.k3d.env ]]; then
+	. $APP_DIR/.k3d.env
+fi
+
+[[ $APP_DIR ]] || { echo "Please pass --app-dir!" 1>&2; exit 1; }
+[[ $BUILD_NAME ]] || { echo "Please configure --build-name!" 1>&2; exit 1; }
+[[ -f $APP_DIR/k3d.conf ]] || { echo "No k3d.conf found in $APP_DIR!" 1>&2; exit 1; }
+
+if ! k3d cluster list "${BUILD_NAME}" 1>/dev/null 2>/dev/null; then
+	k3d cluster create -c "$APP_DIR/k3d.conf"  "${BUILD_NAME}"
+fi
+k3d kubeconfig merge "${BUILD_NAME}" --kubeconfig-merge-default --kubeconfig-switch-context
+
+generate_coredns_custom() {
+	search_domains="$(sed -n -e 's/^search //p' /etc/resolv.conf | tr ' ' '\n' | sed -e 's/\.$//')"
+	nameserver_address="$(sed -n -e 's/^nameserver *//p' /etc/resolv.conf | head -n 1)"
+	cat << _EOF_
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: coredns-custom
+  namespace: kube-system
+data:
+_EOF_
+	for search_domain in $search_domains; do
+		cat << _EOF_
+  ${search_domain}.server: |
+    ${search_domain}{
+      forward . ${nameserver_address}
+    }
+_EOF_
+	done
+}
+
+generate_coredns_custom | kubectl apply -f -
+kubectl rollout restart deployment -n kube-system coredns
+