This is a utility to secure a Linux system by forcing a shutdown under certain conditions. The system must be fully encrypted (except for /boot) so that on boot, a decryption password (or temporarily inserted hardware token) is required. Swap should also be encrypted or non-existent.

• If any one of a configured list of hosts fails ping commands for a certain number of times, the system shuts down.
• If the USB device list changes from the time this script starts, the system shuts down.

When this utility starts, it does a quick check to ensure that all listed hosts can be pinged. If they can't, it exits (rather than shutting down). This is to avoid locking out the rightful owner if there's a legitimate network issue right at startup.

When the service is started, there is a default delay (configurable in the deadman.py) that allows you to remove, for example, a keyboard used for decryption before the service captures the “original” USB device list.

Run install.sh as root. This will:

• Copy the python script to /deadman.py
• Copy the systemd file to /etc/systemd/system/deadman.service
• Reload systemd
• Enable the deadman service
• Start the deadman service
• Copy mount & unmount utility scripts to root's home directory.
  • These scripts are not used by the main logic. They are present to ease manual mounting & unmounting of encrypted volumes.

• Enable on boot: systemctl enable deadman
• Disable on boot: systemctl disable deadman
• Start: systemctl start deadman
• Stop: systemctl stop deadman
• Restart: systemctl restart deadman
• Status: systemctl status deadman -l

All configuration lives near the top of deadman.py. After installation, edit /deadman.py accordingly, then restart the service or reboot to apply changes.

This project includes the following security enhancements:

1. Systemd Hardening:

   • Certain directories are mounted read-only, home directories are protected, and the service has a restricted set of capabilities.
   • See deadman.service for details.

2. Forced Unmount with 1-Second Grace:

   • When shutdown conditions are met, this script tries to unmount /data for up to 1 second.
   • If unmount still hangs (e.g., due to open files), the system proceeds with immediate power-off.
   • These commands are configurable within the global constant shutdown_commands.

3. Global Power-Off Command:

   • The final forced power-off uses a global constant POWER_OFF_COMMAND.
   • You can change this if you prefer a different shutdown tool (for example, poweroff instead of shutdown).

4. Stricter Shell Scripts:

   • Scripts now use set -euo pipefail and absolute paths, reducing the risk of unexpected behaviors or PATH hijacking.

The Python script logs directly to stdout/stderr. Systemd/journald captures this output, which you can view with journalctl -u deadman or systemctl status deadman.

Once installed and running, normal usage does not change. However, be aware that an unexpected change in USB devices or repeated ping failures will cause an immediate shutdown. Ensure your network is stable and that you unplug any devices you don’t need within the startup delay window.