CLN on Windows

[0ceanSlim]

I see CLN is not available for windows as of yet. Is there a timeline for adding this support? Does the support have to do with anything with CLN, or is it just polar that doesn't support it on windows yet?

[jamaljsr]

The reason why CLN has not been supported on Windows is because I couldn't ever get the docker container to run without errors. If I recall correctly, it was caused by the unix socket file lightning-rpc being persisted in the host mounted docker volume that Polar creates. There may be a way to work around it by instructing CLN to store this file in a location outside of the volume mounted dir, but the ramifications of that would need to be investigated. I'm also not sure if Mac/Linux users rely on that file being exposed to the host machine.

Since it's been a pretty long time since I've looked into this, I'd agree it's at least worth looking into it again. Thanks for the feedback.

[Jem256]

Hi @jamaljsr , I've been investigating this and have a working solution. The original hsmd: fsyncdir crash from your 2019 gist has been fixed upstream. But on current CLN (v25.12), the crash has moved to gossipd (my logs). It fails to initialize gossip_store and the node crash loops with STATUS_FAIL_INTERNAL_ERROR: Could not re-initialize gossip_store. The filesystem operations that CLN relies on don't work on Windows Docker bind mounts (9p/virtiofs → NTFS).

The proposed fix: named Docker volumes on Windows
On Windows, instead of bind-mounting ./volumes/c-lightning/<name>/lightningd to the host, we use a named Docker volume (e.g., polar-n1-alice-lightning). Named volumes live on the Docker VM's internal ext4 filesystem, which CLN handles without issue. On Linux/macOS, the existing bind mount is preserved.

The tradeoff is that the CLN data directory isn't directly browsable on the Windows host. However, users can still inspect the data through Docker Desktop's Volumes UI.
I have a working branch with these changes and have confirmed CLN starts and stays online on Windows. I would appreciate your feedback on my approach.