I’m troubleshooting a Docker Desktop startup failure on Windows using WSL2.
Docker Desktop remains stuck on “Starting Docker” and the Docker engine never starts.
The most relevant error I found in the diagnostics is:
bootstrapping wsl: "[2026-06-20T16:33:51.055223633Z][wsl-bootstrap][F] preparing environment: mounting cli-tools iso: running mount -o ro,exec /mnt/docker-desktop-disk/isocache/entries/docker-wsl-cli.iso/... /mnt/host/wsl/docker-desktop/cli-tools: mount: /mnt/host/wsl/docker-desktop/cli-tools: unknown filesystem type 'iso9660'."
Additional symptoms:
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docker versionreturns HTTP 500 errors. -
Docker Desktop reports “WSL bootstrap failed”.
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dockerdandcontainerdnever start inside thedocker-desktopdistribution.
I have also configured a custom WSL2 kernel through .wslconfig:
[wsl2]
kernel=C:Users<user>wsl-kernelcustom_kernel
The kernel was originally built to support an Alfa USB Wi-Fi adapter.
I’ve already tried:
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Reinstalling Docker Desktop
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Rebooting Windows
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Recreating WSL distributions
What could cause Docker Desktop to fail mounting docker-wsl-cli.iso with an unknown filesystem type 'iso9660' error when using a custom WSL2 kernel?
