power-profile-watcher

power-profile-watcher is a small Rust daemon that watches UPower for AC/battery changes and updates power-profiles-daemon automatically:

• AC power: performance
• Battery power: power-saver

It does an initial sync on startup and then only changes profiles when the power source changes. Manual profile changes still work normally until the next plug/unplug event.

Requirements

This program requires these services to be present and running:

• org.freedesktop.UPower
• net.hadess.PowerProfiles

On this machine, those are provided by:

• upower
• power-profiles-daemon

You can verify availability with:

busctl get-property org.freedesktop.UPower /org/freedesktop/UPower org.freedesktop.UPower OnBattery
busctl get-property net.hadess.PowerProfiles /net/hadess/PowerProfiles net.hadess.PowerProfiles ActiveProfile

Build

From the project directory:

cargo build --release

The compiled binary will be:

target/release/power-profile-watcher

Install Binary

Build the binary in this repository:

cargo build --release

Or install it into your Cargo bin directory:

cargo install --path .

The service installer command uses the path of the currently running executable, so it works both when you run the binary from target/release/ and when you run the cargo install copy from ~/.cargo/bin/.

Run Manually

You can test it directly before creating a service:

target/release/power-profile-watcher

You should see log lines when it starts and when it changes profiles.

Stop it with Ctrl+C.

If you installed it with cargo install --path ., run power-profile-watcher instead.

Install As A systemd User Service

Use the built-in installer command:

target/release/power-profile-watcher install-service

If you installed it with cargo install --path ., run:

power-profile-watcher install-service

This writes ~/.config/systemd/user/power-profile-watcher.service, reloads the user manager, and runs systemctl --user enable --now power-profile-watcher.service.

The generated unit sets Environment=RUST_LOG=info, so it emits normal log output by default.

Verify

Check service status:

systemctl --user status power-profile-watcher.service

Watch service logs:

journalctl --user -u power-profile-watcher.service -f

Check the current active profile:

powerprofilesctl get

Then test the actual behavior:

1. Plug in AC power and confirm the profile becomes performance.
2. Unplug AC power and confirm the profile becomes power-saver.
3. Manually change the profile in GNOME and confirm it stays changed until the next AC state transition.

Update After Code Changes

After modifying the program:

cargo build --release
target/release/power-profile-watcher install-service

Uninstall

Remove the user service with the built-in command:

target/release/power-profile-watcher uninstall-service

If you installed it with cargo install --path ., run:

power-profile-watcher uninstall-service

This disables the service, removes ~/.config/systemd/user/power-profile-watcher.service, and reloads the user manager.

Notes

• This program is not GNOME-specific. It works anywhere UPower and power-profiles-daemon are available.
• It uses direct D-Bus calls instead of spawning powerprofilesctl.
• It is event-driven. It does not poll.