Btw, a hack you can do here that preserves the old behavior is:

```
if head -n 1 $TMP | grep -q '^#!'; then
    echo "Executing user-data as script at ${TMP}"
    chmod +x $TMP
    $TMP

    if grep -q '^ETCD_DISCOVERY_URL=' $TMP; then
        eval $(grep  '^ETCD_DISCOVERY_URL=' $TMP | tail -n1)
    fi
fi
```