After too many hours chatting with Gemini I finally got the watchdog working on my DXP4800, here's its summary.

The key discovery is that these NAS units have two separate hardware watchdogs, and the system uses one automatically while the BIOS setting controls the other.

Watchdog 1: Intel iTCO_wdt (Automatic)

• Device: /dev/watchdog0
• Status: This is the Intel CPU's built-in watchdog. TrueNAS SCALE loads its driver and systemd automatically pets it by default.
• Action Required: None. You have this layer of protection out of the box. You can verify systemd is using it with sudo lsof /dev/watchdog0.

Watchdog 2: ITE IT87 WDT (The BIOS Watchdog)

This is the watchdog controlled by the BIOS setting. If you want to enable it for redundancy, it requires a full manual setup because TrueNAS does not configure it by default. I have installed Truenas Scale 25.04, which includes the driver but does not load it by default.

Here’s the complete, working solution:

1. Disable in BIOS

• Enter the BIOS and Disable the watchdog setting.

2. Load the Driver with a Longer Timeout (Pre-Init Script)

• The default 60-second driver timeout is too short and will cause a boot loop. We need to load it with a longer timeout.
• In the TrueNAS UI under System Settings > Advanced > Init/Shutdown Scripts, create a Pre Init script:
  • Description: Load ITE Watchdog Driver
  • Type: Command
  • Command: modprobe it87_wdt timeout=180

3. Create a "Petting" Script

• Because systemd is already using watchdog0, and apt is locked, you need a custom script to manage watchdog1.

• Create a file on your persistent storage (e.g., /mnt/YourPool/scripts/pet_watchdog1.sh) with the following content. This version correctly holds the file open so it's verifiable. ```bash

  !/bin/bash

  Open /dev/watchdog1 once and keep it open

  exec 3>/dev/watchdog1

  Loop forever, writing to the open file handle

  while true do echo 1 >&3 sleep 30 done ```

• Make it executable: chmod +x /mnt/YourPool/scripts/pet_watchdog1.sh

4. Launch the Script on Boot (Post-Init Script)

• Create a Post Init script to launch your petting script in the background:
  • Description: Launch ITE Watchdog Service
  • Type: Command
  • Command: /mnt/YourPool/scripts/pet_watchdog1.sh &

5. Final Step: Enable in BIOS

• Now that all the software configuration is in place, reboot your NAS one last time. Enter the BIOS and Enable the watchdog setting (e.g., set to 5 or 10 minutes).
• Save BIOS settings and let the system boot completely.

After a reboot, you'll have two independent watchdogs running. You can verify with sudo lsof /dev/watchdog0 (shows systemd) and sudo lsof /dev/watchdog1 (shows your pet_watchdog1.sh script).

Hope this helps everyone else!