wsl-tray

Windows tray icon that shows whether the WSL2 VM is running and how much CPU and memory it uses, with a menu entry that shuts it down.

It sits next to the clock like the keyboard-layout badge. Grey means the WSL2 VM is off; green, orange or red means it is running and shows how much of the machine it is using.

Left to right: off, running below 50 %, 50–75 %, above 75 %.

Percentages are relative to the whole machine (all logical cores, all physical RAM), the same way Task Manager reports vmmemWSL. The colour follows whichever of CPU or memory is higher.

Hover for the numbers:

Click (left or right) for the menu:

Shut down WSL2 runs wsl --shutdown after asking for confirmation. Start with Windows adds or removes an entry under HKCU\Software\Microsoft\Windows\CurrentVersion\Run.

Download

  

  

The buttons always fetch the latest release. Each release has four executables attached, wsl-tray-win11-x64.exe, wsl-tray-win11-arm64.exe, wsl-tray-win10-x64.exe and wsl-tray-win10-arm64.exe, with a SHA256SUMS file. There is nothing to install: put the file somewhere permanent, run it, and tick Start with Windows in the menu if you want it back after a reboot. It does not need administrator rights.

The Windows 11 and Windows 10 builds differ in one thing only: the name of the VM process they look for, vmmemWSL or vmmem. If the icon stays grey while a distribution is running, look the process up in Task Manager (Details tab) and take the other build, or pass the name with -process.

On Windows 11 the icon shows up next to the clock on first run (the app sets its own IsPromoted flag in HKCU\Control Panel\NotifyIconSettings, but only if you have not already decided about it in Settings › Taskbar).

Sponsoring

If wsl-tray is useful to you, you can support its development:

  

Command line

wsl-tray.exe [-poll 5s] [-interval 30s] [-process vmmemWSL] [-log FILE] [-render-test DIR]

Flags can be written as -poll 10s, -poll=10s or --poll 10s. Durations are written like 30s, 1m30s or 250ms.

Resource usage

Measured on Windows 11 25H2, AMD Ryzen AI MAX+ 395 (32 logical cores, 48 GB), 125 % display scaling, with the release build from this repository.

The only dependency is windows-sys, which contains nothing but extern declarations. There is no runtime, no COM, no allocation on the poll path beyond reusing one buffer.

For comparison, the original Go version of this program was a 2.4 MB executable using 16 MB of private memory and 8 threads; the difference is the Go runtime.

Measure it yourself: cargo test --release -- --ignored --nocapture poll_cost prints the per-poll cost on your machine.

How it works

• The VM shows up as a process called vmmemWSL (vmmem on Windows 10). Its presence is the on/off signal. wsl --list --running is not used because it says "no running distributions" while the VM is still alive and holding memory.
• CPU and memory come from NtQuerySystemInformation(SystemProcessInformation), the call Task Manager uses. It needs no handle to the process, which matters because vmmemWSL runs as SYSTEM and OpenProcess on it is denied to a normal user. CPU is the difference in kernel+user time between two samples divided by wall time and the number of logical cores; memory is the process's working set.
• The icon is the Font Awesome "linux" glyph, rasterized once into a small coverage mask (assets/tux.bin, generated by tools/gentux-rs) and scaled to the taskbar's icon size at run time. No font is involved, so it looks the same on every machine.
• wsl --shutdown is started with CreateProcessW and an explicit System32\wsl.exe path, without a console window.

Building

You need a stable Rust toolchain (1.88 or newer) with the MSVC target.

.\build.ps1

This runs cargo build --release and copies the result to .\wsl-tray.exe. Run that copy rather than the one under target\: Windows refuses to overwrite a running executable, so running from target\release makes the next build fail while the tray app is open.

.\build.ps1 -Win10 (or cargo build --release --features win10) builds the Windows 10 variant. The win10 feature does nothing but change the default of -process from vmmemWSL to vmmem.

The exe icon, the application manifest (per-monitor DPI, common controls v6) and the version resource are linked from pre-built objects in res\ (one per architecture), so rc.exe is not needed. To regenerate them after editing winres\:

go install github.com/tc-hib/go-winres@latest
go-winres make --in winres/winres.json --arch amd64,arm64 --out res/wsl-tray
Move-Item res\wsl-tray_windows_amd64.syso res\wsl-tray-amd64.res.obj -Force
Move-Item res\wsl-tray_windows_arm64.syso res\wsl-tray-arm64.res.obj -Force

To regenerate the icon mask after changing tools\gentux-rs\linux.svg or the stroke width:

cd tools\gentux-rs
cargo run --release

Tests and CI

cargo test --release runs the unit tests, including one that samples live processes on the machine. The GitHub Actions workflow builds the Windows 11 and Windows 10 variants for x64 and ARM64 on every push, runs the tests and clippy, and attaches all four executables to a release when a v* tag is pushed.

Layout

src/main.rs        window, tray icon, menu, autostart, Windows 11 promotion
src/monitor.rs     process sampling, wsl --shutdown
src/icon.rs        mask scaling, HICON creation, PNG output for -render-test
assets/tux.bin     icon mask (generated)
res/               resource objects; winres/ has their sources
tools/gentux-rs/   mask generator
docs/              screenshots

Each source file starts with a module comment that explains its part of the program (the message flow and re-entrancy rules in main.rs, why the process list is read the way it is in monitor.rs, the icon pipeline in icon.rs). cargo doc --document-private-items --open renders all of it.

License

BSD 3-Clause, see LICENSE. The Tux glyph is the "linux" icon from Font Awesome Free, CC BY 4.0; see THIRD_PARTY_NOTICES.md.