The Complete WinNUT Guide: Connect Windows to Your NUT Server
Network UPS Tools (NUT) is the gold standard for managing uninterruptible power supplies (UPS) on Linux servers and Network Attached Storage (NAS) devices. However, keeping your Windows workstations safe during a power outage requires a bridging tool.
WinNUT-Client is a free, open-source Windows application that connects your PC to a central Linux NUT server. This guide will show you how to install, configure, and automate WinNUT to ensure your Windows machine shuts down safely before your battery dies. Prerequisites: What You Need First
Before configuring your Windows client, ensure your primary NUT server is fully operational.
NUT Server IP: The local IP address of your Linux or NAS system hosting the UPS.
UPS Name: The exact identifier defined in your server’s ups.conf file.
MONUSER Credentials: The username and password created in your server’s upsd.users file, explicitly granted upsmon master or upsmon slave privileges.
Network Connectivity: Ensure port 3493 (the default NUT port) is open through your server’s firewall. Step 1: Download and Install WinNUT
The original WinNUT project is legacy software. You must use the modern, actively maintained fork called WinNUT-Client.
Navigate to the official WinNUT-Client repository on GitHub. Download the latest .msi installer from the Releases page. Launch the installer on your Windows machine. Follow the setup wizard prompts. Complete the installation and launch the application. Step 2: Configure the Server Connection
When you open WinNUT-Client for the first time, you will see a main status dashboard showing a disconnected state. Click on Settings in the top menu bar. Locate the Connection Settings section. Enter your NUT server details into the fields: Host: Type your NUT server’s IP address. Port: Type 3493 (unless customized on your server). UPS Name: Type the exact name of your UPS. Username: Enter your NUT monitor username. Password: Enter your NUT monitor password. Click Apply and then OK.
Click Connect on the main dashboard to verify the status changes to OL (On Line). Step 3: Set Up Shutdown Triggers and Timers
You must define exactly how Windows behaves when the power goes out. WinNUT allows you to delay the shutdown sequence to ride out brief power flickers. Reopen the Settings menu. Navigate to the Shutdown tab. Configure your timing preferences:
Shutdown Delay: Set the number of seconds Windows waits after the UPS switches to battery power before initiating a shutdown. A value of 60 or 120 seconds is ideal for short outages.
Low Battery Shutdown: Check this box to force an immediate shutdown if the NUT server reports the UPS battery is critically low (LB), bypassing your standard delay timer. Define the execution command:
By default, WinNUT uses shutdown.exe /s /t 0 /f to safely and immediately turn off the PC. Leave this as default unless you need to trigger a custom script. Step 4: Automate WinNUT as a Windows Service
For reliable protection, WinNUT must run in the background automatically, even if no user is actively logged into the Windows machine. Open Settings and go to the Application or General tab. Check the box labeled Start minimized. Check the box labeled Start with Windows.
To run it completely independent of user logins, look for the Install as Service button.
Click Install Service (this requires administrative privileges).
Verify the service is running by opening the Windows Services manager (services.msc) and ensuring the WinNUT Client Service status is set to Running and the Startup Type is Automatic. Testing Your Configuration
Never wait for a real power outage to find out if your configuration works. Save all open work on your Windows PC. Unplug your UPS from the wall outlet.
Monitor the WinNUT dashboard; the status should immediately switch from OL (On Line) to OB (On Battery).
Watch the countdown timer trigger based on your Step 3 settings.
Let the timer expire to confirm Windows initiates a clean, safe shutdown. Plug the UPS back into the wall and restart your computer. Troubleshooting Common Errors “Access Denied” or Connection Refused
Fix: Double-check your upsd.users file on the server. Ensure the IP address of your Windows machine is permitted to connect in your server’s access control configuration. WinNUT Disconnects Frequently
Fix: Increase the Timeout and Retry Interval settings inside the WinNUT Connection settings tab. Wireless networks or busy local networks can cause brief packet drops. Windows Fails to Shut Down
Fix: Ensure WinNUT is running with Administrator privileges. If running as a standard desktop application, it lacks the system authority to execute the shutdown command. Converting it to a Windows Service resolves this issue.
To make sure your specific UPS model works perfectly with this setup, tell me: What brand and model of UPS are you using?
What operating system (TrueNAS, Ubuntu, Unraid, etc.) is hosting your NUT server?
Do you have multiple Windows PCs that need to connect to this same server?
I can provide the exact server configuration snippets or batch scripts tailored to your hardware.
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