ensure user is setup in preinstall hook

scripts/pre-install.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+
+OS="$(uname -s)"
+
+if [ "${OS}" = "Linux" ]; then
+    # Make a user and group for this app, but only if it does not already exist.
+    id unpoller >/dev/null 2>&1  || \
+        useradd --system --user-group --no-create-home --home-dir /tmp --shell /bin/false unpoller
+elif [ "${OS}" = "OpenBSD" ]; then
+    id unpoller >/dev/null 2>&1  || \
+        useradd  -g =uid -d /tmp -s /bin/false unpoller
+elif [ "${OS}" = "FreeBSD" ]; then
+    id unpoller >/dev/null 2>&1  || \
+        pw useradd unpoller -d /tmp -w no -s /bin/false
+else
+    echo "Unknown OS: ${OS}, please add system user unpoller manually."
+fi