use pm2 with systemd to make pingvin-share survive reboots (#3935)

install/pingvin-install.sh

@@ -47,7 +47,10 @@ sed -i '/"admin.config.smtp.allow-unauthorized-certificates":\|admin.config.smtp
 $STD npm install
 $STD npm run build
 $STD pm2 start --name="pingvin-share-frontend" npm -- run start
-$STD pm2 startup
+# create and enable pm2-root systemd script
+$STD pm2 startup systemd 
+# save running pm2 processes so pingvin-share can survive reboots
+$STD pm2 save
 msg_ok "Installed Pingvin Share"
 
 motd_ssh