Add dependency check for docker & compose

_common/functions.sh

@@ -7,3 +7,14 @@ pushd () {
 popd () {
     command popd "$@" > /dev/null
 }
+
+check_deps () {
+    if ! which docker > /dev/null; then
+        echo "ERROR: docker is not installed."
+        exit 1
+    fi
+    if ! docker compose version > /dev/null; then
+        echo "ERROR: docker compose is not installed, or is too old."
+        exit 1
+    fi
+}

cluster/start.sh

@@ -15,6 +15,8 @@ SCRIPTPATH="$( cd "$(dirname "$0")"; pwd -P )"
 
 source "$SCRIPTPATH/../_common/functions.sh"
 
+check_deps
+
 while getopts n:h o; do
   case "$o" in
     n)