IDLE-CPU-SAVE SYSTEMD SERVICE

Systemd service/timer workflow that switches CPU governors when the user becomes idle or active.

Installation

1. Copy the provided .config and .local folders into your home directory:

   cp -rv .config ~/
   cp -rv .local ~/
   chmod +x ~/.local/bin/idle-cpu-save.sh

2. Confirm cpupower binary location:

   which cpupower || command -v cpupower

3. Add a sudoers rule (requires root) allowing execution of cpupower:

   echo "$(whoami) ALL=(root) NOPASSWD: $(which cpupower)" | sudo tee /etc/sudoers.d/50-idle-cpu-save

   Verify produced file syntax with:

   sudo visudo -c -f /etc/sudoers.d/50-idle-cpu-save

4. Reload and enable the timer/service (user-level):

   systemctl --user daemon-reload
   systemctl --user enable --now idle-cpu-save.timer

Configuration

After changing any configuration be sure to reload with systemctl --user daemon-reload

• Configure desired active and idle governors

  Use the GOV_IDLE and GOV_ACTIVE environment variables in idle-cpu-save.service.
  Set to correct values like powersave, performance, schedutil, ondemand depending on your kernel and cpupower support.
  Run cpupower frequency-info to check.

• Configure idle and active thresholds Use the IDLE_THRESHOLD_MS environment variable in idle-cpu-save.service to set the idle detection threshold (default: 120000ms = 2 minutes).
  Use the ACTIVE_THRESHOLD_MS environment variable to set the active detection threshold after coming from idle (default: 20000ms = 20 seconds). This allows faster switch to active state.

Troubleshooting

• Test the cpupower command directly:

   sudo /usr/bin/cpupower frequency-set -g schedutil

• Check current governor from sysfs (no root usually required for read):

   cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

• Inspect logs:

   journalctl --user -u idle-cpu-save.service -u idle-cpu-save.timer --since "5 minutes ago" --follow

• Start the service manually for testing:

   systemctl --user start idle-cpu-save.service
   journalctl --user -u idle-cpu-save.service --since "5 minutes ago"

• Desperate Mode (enabled extra logging):

   DEBUG=1 systemctl --user set-environment DEBUG=1
   systemctl --user daemon-reload
   journalctl --user -u idle-cpu-save.service --follow

  Cleanup when done:

   systemctl --user unset-environment DEBUG

Uninstall

1. Stop and disable the timer (user-level):

   systemctl --user disable --now idle-cpu-save.timer

2. Remove the service and timer files:

   rm ~/.config/systemd/user/idle-cpu-save.service
   rm ~/.config/systemd/user/idle-cpu-save.timer
   systemctl --user daemon-reload

3. Remove the script:

   rm ~/.local/bin/idle-cpu-save.sh

4. Remove the sudoers rule:

   sudo rm /etc/sudoers.d/50-idle-cpu-save

5. (optional) Restore a default CPU governor:

   sudo /usr/bin/cpupower frequency-set -g powersave

   check available governors with: cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors