add a preset, although it doesn't seem necessary

install.sh

@@ -9,7 +9,7 @@ cd "${dir}"
 BINARY=$(curl https://api.github.com/repos/prometheus/node_exporter/releases/latest | jq -r '.assets[] | select(.name | contains("linux-amd64")) | .browser_download_url')
 curl -L $BINARY -o node-exporter.tgz
 
-mkdir -p prometheus/usr/{bin,lib/{systemd/system,extension-release.d}}
+mkdir -p prometheus/usr/{bin,lib/{systemd/{system,system-preset},extension-release.d}}
 tar xzf node-exporter.tgz
 
 cp -vrf node_exporter-*/node_exporter prometheus/usr/bin/node_exporter
@@ -31,6 +31,11 @@ ProtectSystem=strict
 WantedBy=multi-user.target
 EOM
 
+cat > prometheus/usr/lib/systemd/system-preset/00-prometheus-node-exporter.preset <<- EOM
+# enabling prometheus
+enable prometheus-node-exporter.service
+EOM
+
 source /etc/os-release
 echo -e "SYSEXT_LEVEL=1.0\nID=steamos\nVERSION_ID=${VERSION_ID}" >> prometheus/usr/lib/extension-release.d/extension-release.prometheus-node-exporter