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Analyzing WSLg logs

WSLg is the component that runs graphical (GUI) and audio Linux applications on WSL. Its source lives in a separate repository: https://github.com/microsoft/wslg. The canonical list of diagnostics to request for a WSLg bug is the WSLg repo bug report template (.github/ISSUE_TEMPLATE/bug_report.yml in microsoft/wslg).

diagnostics/collect-wsl-logs.ps1 collects the logs into a wslg/ subfolder of the log archive (via wsl.exe --system --user root, with a timeout so a wedged service can't hang collection), so a standard WSL log collection already contains the log files below. Crash dumps (dumps/, wsl-crashes/) are only collected when the script is run with -Dump.

Architecture (just enough to read the logs)

WSLg runs a system distro (a small Azure Linux VM, separate from the user distro) that hosts: - weston (Wayland compositor) with the rdp-backend.so / rdprail-shell.so modules - Xwayland for X11 apps - pulseaudio with an RDP sink/source for audio - FreeRDP to stream the surfaces over an hvsocket to the Windows RDP client (msrdc.exe)

weston.log and wlog.log are written by weston/FreeRDP, pulseaudio.log by pulseaudio, and stderr.log is the combined stderr of WSLGd and the processes it launches.

Files (in the wslg/ folder, sourced from /mnt/wslg)

File Contents
versions.txt WSLg version, architecture, build date, component git hashes (weston, FreeRDP, mesa, pulseaudio)
weston.log Weston compositor + RDP backend log
wlog.log FreeRDP (WLog) log
pulseaudio.log PulseAudio log
stderr.log WSLGd and child-process stderr
dumps/ Legacy WSLg crash dumps (older builds only; collected with -Dump)
wsl-crashes/ Host-side WSLg crash dumps copied from %TEMP%\wsl-crashes (newer builds, e.g. core.weston; collected with -Dump)

Reading tips and common signatures

  • weston.log is truncated on every boot. Weston is started with --log=/mnt/wslg/weston.log and opens it truncating, so the file only ever contains the latest system-distro boot. To tell whether weston restarted, compare the boot timestamp on the first line (weston 9.0.0 ...) across snapshots, or correlate with dmesg.

  • System distro cycling / teardown. In dmesg (collected via the ETL GuestLog events or the debug console), this pair means the WSLg system distro's init exited and the distro was torn down (idle timeout or shutdown), which also restarts weston: Exception: Operation canceled @p9io.cpp:258 (AcceptAsync) WSL (1 - init()) ERROR: InitEntryUtilityVm:2551: Init has exited. Terminating distribution Repeating every ~25-60s with no GUI client attached is usually normal idle teardown, not a crash. A genuine weston crash instead leaves a core dump in wsl-crashes/ (or dumps/).

  • No GPU acceleration (software rendering). This means the virtual GPU (/dev/dxg, d3d12 mesa) is not usable, so rendering falls back to CPU: Xwayland glamor: GBM Wayland interfaces not available Failed to initialize glamor, falling back to sw Investigate GPU driver presence, /dev/dxg, and the mesa/d3d12 stack if the user reports black windows, slow rendering, or missing 3D.

  • Audio sink not connected (usually benign at boot). Expected until an RDP/audio client attaches: [rdp-sink] RDP Sink - Trying to connect to /mnt/wslg/PulseAudioRDPSink [rdp-sink] Connected failed If it persists while audio is actively broken, look at the RDP client (msrdc) audio channel.

  • Mostly-benign startup noise (not a root cause on its own):

    • WSLGd: Exception: No such file or directory @FontMonitor.cpp:280 - font share not mounted.
    • XDG_RUNTIME_DIR "/mnt/wslg/runtime-dir" ... mode 040777 (should be 0700) - common warning.
    • dbus: Unknown username "pulse" / Option "-listen" is deprecated - harmless.

When to escalate to the WSLg repo

WSLg code is not in this repository. Fixes to weston, FreeRDP, pulseaudio, or the RDP backend belong in https://github.com/microsoft/wslg. Use a commit-pinned permalink when referencing files there so the link does not drift, e.g. https://github.com/microsoft/wslg/blob/<commit-sha>/<path>.