Auto lock screen if your smartphone is not connected via USB.
Tested on Arch Linux + Cinnamon but should be trivial to accommodate for any Linux distribution.
One of the most likely and severe security fuckups is simply forgetting to lock your desktop. The time-based locking is far not enough in most environments. Ideally, desktop should lock immediately when you depart from the computer. These simple scritps implement exactly that: locking the screen out when you disconnect the smartphone.
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You always get your smartphone with you when you leave your computer.
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You always connect your smartphone back with the USB cable when you come back to your computer (for charging, etc).
Connect your smartphone with USB cable.
Learn your smartphone serial number when connected as USB device:
lsusb # list all USB devices
lsusb -v # list all USB devices with full details
Create /etc/lock-unless-smartphone.conf with the serial number of your smartphone:
#!/bin/bash
export USB_DEVICE_SERIAL_NUMBER=XDE1231423 # replace with your smartphone S/N
Symlink *.service and *.timer files to /usr/lib/systemd/system/ respectively.
Enable and start the timer:
sudo systemctl enable lock-unless-smartphone.timer
sudo systemctl start lock-unless-smartphone.timer
Test the setup by disconnecting the smartphone cable. The desktop should lock in under 4 seconds. If not, debug with journalctl -r, systemctl list-timers, systemctl status lock-unless-smartphone.timer etc.