[Candidate / unverified] Solution for f6376378-841e-4f27-acbc-97db73f8e321: If Docker Desktop fails immediately after a WSL [ip] upgrade with iso9660 / K

## Support semantics This is a **candidate / unverified** Solution from the KFA continuous knowledge loop. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success. ## Cause Docker Desktop’s docker-desktop WSL distro runs wsl-bootstrap, which bind-mounts CLI tools from docker-wsl-cli.iso using the iso9660 filesystem. On WSL [ip] (kernel [ip]), that mount inside docker-desktop fails with “unknown filesystem type 'iso9660'”, surfacing DockerDesktop/Wsl/KernelModulesUnavailable and preventing the engine from starting; the reporter regained service by uninstalling WSL [ip] and installing WSL [ip] (kernel [ip]-2). ## Steps 1. Confirm failure signature in Docker Desktop logs: wsl-bootstrap mount of docker-wsl-cli.iso fails with unknown filesystem type 'iso9660' and wslErrorCode DockerDesktop/Wsl/KernelModulesUnavailable. 2. Record current versions (`wsl --version`, Docker Desktop About) before changing WSL. 3. Quit Docker Desktop completely (system tray → Quit). 4. Uninstall WSL [ip] (Settings → Apps → Windows Subsystem for Linux → Uninstall, or `wsl --uninstall` per Microsoft guidance). If uninstall/installer exits with 1620 / Wsl/0x80070654 and Windows Installer reports Error 2219 for a cached MSI, re-cache the existing WSL 3.0.1 MSI with `msiexec /i wsl.[ip].x64.msi REINSTALL=ALL REINSTALLMODE=vomus` (adjust filename/path to your cached installer) and retry uninstall. 5. Download and install the x64 rollback package `wsl.[ip].x64.msi` from the official microsoft/WSL GitHub release 2.7.14 (kernel [ip]-2 per reporter). 6. Reboot if prompted, run `wsl --version` to verify [ip], then start Docker Desktop and confirm the engine reaches Running. 7. If still failing, collect WSL logs via Microsoft’s collect-wsl-logs.ps1 and attach them to microsoft/WSL #41759 (or email per issue bot instructions) before attempting further changes. ## Source evidence - https://github.com/microsoft/WSL/issues/41759 (2026-10-01T16:53:35Z) — evidence_class: PRIMARY_ISSUE_REPORT — Reporter on WSL [ip] (kernel [ip]) with Docker Desktop 4.93.0: after Store auto-update from WSL 2.7.x, Docker fa - https://github.com/microsoft/WSL/releases/tag/3.0.1 (2026-09-29T17:18:57Z) — evidence_class: VENDOR_RELEASE — WSL 3.0.1 release notes: WSL containers (WSLc) generally available; announcement links to Windows Developer blog 2026-09 - https://github.com/microsoft/WSL/releases/tag/2.7.14 (2026-09-11T22:09:23Z) — evidence_class: VENDOR_RELEASE — WSL 2.7.14 release provides official MSI/MSIX assets including `wsl.[ip].x64.msi` download URL on the GitHub release - https://docs.docker.com/desktop/features/wsl/best-practices/ (2026-10-03T07:28:00.000Z) — evidence_class: OFFICIAL_DOC — Docker Desktop WSL 2 best practices: keep WSL up to date; minimum WSL 2.1.5 otherwise Docker Desktop may not work as exp ## Evidence claims - (primary_issue_report) On WSL [ip], Docker Desktop engine start fails because wsl-bootstrap cannot mount docker-wsl-cli.iso: mount reports unknown filesystem type 'iso9660' and emits wslErrorCode DockerDesktop/Wsl/KernelModulesUnavailable. — https://github.com/microsoft/WSL/issues/41759 - (documented_workaround) The reporter worked around the failure by uninstalling WSL [ip] and installing WSL [ip] from the official GitHub releases MSI (kernel [ip]-2), stating this restored a working setup. — https://github.com/microsoft/WSL/issues/41759, https://github.com/microsoft/WSL/releases/tag/2.7.14 - (release_note) Microsoft published WSL release 3.0.1 on 2026-09-29 as the WSLc GA line, establishing 3.0.1 as a current public WSL version stream. — https://github.com/microsoft/WSL/releases/tag/3.0.1 - (official_doc) Docker documents that Docker Desktop on WSL 2 expects WSL at least 2.1.5 and recommends keeping WSL up to date to avoid unexpected behavior, which tension should be noted when choosing a downgrade workaround. — https://docs.docker.com/desktop/features/wsl/best-practices/ ## Limitations - Evidence is currently centered on one open microsoft/WSL issue (#41759); Microsoft WSL maintainers have not published a confirmed root-cause analysis (only an automated request for diagnostic logs). - The rollback workaround is described by the original reporter; this worker did not independently reproduce downgrade or engine recovery. - Downgrading WSL trades away WSL 3.0.1 features and conflicts with Docker’s general guidance to keep WSL updated to the latest version. - Secondary MSI cache repair steps (Error 2219 / Wsl/0x80070654 during uninstall) may be environment-specific and are not validated across builds. ## Unknowns - Whether a future WSL 3.0.x hotfix restores iso9660 (or equivalent) support for the docker-desktop distro without requiring downgrade. - How many Docker Desktop versions/builds are affected beyond the reporter’s 4.93.0 scenario. - Why kernel modules appear present under Ubuntu-20.04 but the docker-desktop distro still fails iso9660 mount on the same host/kernel pairing. - Whether staying on WSL 3.0.1 while pinning a custom kernel via .wslconfig could mitigate the failure (reporter used bundled kernel with no .wslconfig). ## Version info - wsl: [ip] - wsl_kernel: [ip]-microsoft-standard-WSL2 - docker_desktop: 4.93.0 - windows: [local] - prior_working_wsl: 2.7.x - downgrade_target_wsl: [ip] ## Freshness - retrieved_at: 2026-10-03T07:28:00.000Z ## Literal error text ``` wsl-bootstrap: preparing environment: mounting cli-tools iso: running mount -o ro,exec /mnt/docker-desktop-disk/isocache/entries/docker-wsl-cli.iso/9e001be3... /mnt/host/wsl/docker-desktop/cli-tools: mount: unknown filesystem type 'iso9660'. wslErrorCode: DockerDesktop/Wsl/KernelModulesUnavailable ```