NoUPSPoweroff

Problem Statement

The in house server is powered by a basic UPS that lacks advanced monitoring capabilities. To ensure the server can be gracefully shut down during a power outage, we need an external method to monitor the power state by using the battery status of another device (e.g., laptop).

Solution Evaluation

Benefits:

• No additional hardware needed
• Simple implementation
• Quick response to power outages

Considerations:

• Depends on the laptop being operational
• Single point of monitoring
• Network connectivity required

Warning

When executing sudo poweroff, this assumes the hypervisor can gracefully shut down VMs (e.g., Proxmox). Make sure your hypervisor supports this.

Prerequisites

• Linux with systemd
• acpi package (sudo apt install acpi)
• SSH key-based authentication configured
• Passwordless sudo on the UPS powered server

Installation

1. Clone the repository and prepare the script:

   git clone https://github.com/vwkyc/NoUPSPoweroff.git
   cd NoUPSPoweroff
   chmod +x NoUPSPoweroff.sh

Configuration

1. Edit the configuration file NoUPSPoweroff.conf:

   • General Settings:
     • minutes: Time to wait before shutdown when on battery (default: 25)
     • sleep_interval: Sleep interval between checks in seconds (default: 5)
     • status_interval: Status update interval in seconds (default: 120)
     • min_battery: Minimum battery percentage before immediate shutdown (default: 10)
     • ac_stable_time: AC power stability time before cancelling shutdown in seconds (default: 300 = 5 minutes)
   • File Paths: All temporary files use unique noupspoweroff_ prefixes to prevent conflicts
   • Servers: Define multiple servers to shutdown with [serverN] sections

2. Edit username in NoUPSPoweroff.service

3. Install the script and service:

   sudo install -m 755 NoUPSPoweroff.sh /usr/local/bin/
   sudo cp NoUPSPoweroff.service /etc/systemd/system/
   sudo cp NoUPSPoweroff.conf /etc/
   sudo systemctl daemon-reload
   sudo systemctl enable NoUPSPoweroff.service --now

ssh Poweroff

Allow passwordless poweroff on the UPS powered server:

1. Allow the user USERNAME to execute sudo poweroff without a password:

   sudo visudo

2. Add the following line at the end:

   USERNAME ALL=(ALL) NOPASSWD: /sbin/poweroff, /sbin/reboot, /sbin/shutdown
   

UPS Runtime Calculation

To determine the appropriate MINUTES value for the script, you need to calculate the expected runtime of your server on the UPS. Follow these steps:

1. Identify Your Server's Power Consumption:

   • Measure the power usage of your server in watts (W). This can be found in the server's documentation or by using a power meter.

2. Determine Your UPS Battery's Capacity:

   • Find the battery's capacity, typically expressed in ampere-hours (Ah) and voltage (V). This information is usually provided by the UPS manufacturer.

3. Calculate the Battery's Total Energy Storage:

   • Use the formula:

     Battery Energy (Wh) = Battery Capacity (Ah) × Battery Voltage (V)
     

4. Estimate the UPS Runtime:

   • Apply the formula:

     Runtime (hours) = Battery Energy (Wh) / Server Power Consumption (W)
     

   • Convert the runtime to minutes by multiplying by 60.

Example Calculation

Assume your server consumes 90 W, and your UPS has a battery capacity of 7.0 Ah at 12 V:

1. Calculate Total Battery Energy:

   7.0 Ah × 12 V = 84 Wh
   

2. Determine Runtime:

   Runtime (hours) = 84 Wh / 90 W = 0.933 hours = 56 minutes
   

In this scenario, the estimated runtime is approximately 56 minutes. To ensure a safe shutdown before the UPS battery is fully depleted, it's advisable to set the minutes variable in your configuration to a value slightly less than this estimate, accounting for factors like battery aging and efficiency losses.

Power Restoration Behavior

When AC power is restored after a power outage:

1. Immediate Detection: The script detects AC power restoration immediately
2. Stability Period: AC power must remain stable for 5 minutes (configurable via ac_stable_time) before cancelling any pending shutdown
3. Progress Updates: During the stability period, the script logs progress every check interval
4. Power Flicker Protection: If power is lost again during the stability period, the timer resets
5. Shutdown Cancellation: Only after the full stability period does the script cancel the pending shutdown

This prevents false cancellations from brief power flickers or unstable power conditions.

Status & Logs

Monitor the service status and logs:

systemctl status NoUPSPoweroff.service
journalctl -u NoUPSPoweroff.service -f

Troubleshooting

1. Check permissions:

   ls -l /usr/local/bin/NoUPSPoweroff.sh

2. Check logs:

   journalctl -u NoUPSPoweroff.service -f

Uninstallation

To disable and remove the NoUPSPoweroff service, follow these steps:

1. Stop and disable the service:

   sudo systemctl stop NoUPSPoweroff.service
   sudo systemctl disable NoUPSPoweroff.service

2. Remove the service file and script:

   sudo rm /etc/systemd/system/NoUPSPoweroff.service
   sudo rm /usr/local/bin/NoUPSPoweroff.sh

3. Reload the systemd daemon to apply changes:

   sudo systemctl daemon-reload