fix: fall back to fusermount when /dev/fuse is inaccessible#1
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fuse_mount_sys already falls back to fusermount on mount(2) EPERM, but returns a hard error when DevFuse::open() fails. This means unprivileged containers that lack /dev/fuse but have a (possibly proxied) fusermount binary never reach the fallback path. Return Ok(None) on NotFound/PermissionDenied from DevFuse::open() so the caller retries via fusermount, matching the mount(2) behavior.
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This was referenced Apr 28, 2026
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Can you push this on upstream fuser ? I would like to push my commit too |
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Merging for now |
XciD
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## Summary Bumps the pinned `fuser` SHA on the `sidecar-multi-fd` branch of `huggingface/fuser` to pick up [PR #1](huggingface/fuser#1), which makes `fuse_mount_pure` fall back to `fusermount` when `DevFuse::open()` returns `NotFound` or `PermissionDenied`. Previously the fallback path only fired on `mount(2) EPERM`, so an inaccessible `/dev/fuse` (typical in unprivileged Kubernetes pods) bailed out hard before fusermount was ever tried. Closes #147. Unblocks [skypilot-org/skypilot#9418](skypilot-org/skypilot#9418). ## Verification Reproduced on an AL2023 EC2 box by `chmod 0` on `/dev/fuse` (simulating an unprivileged container with no device access): Before: ``` ERROR Permission denied: mounting a FUSE filesystem requires root privileges. Try running with: sudo ... ERROR FUSE mount failed: Permission denied (os error 13) ``` After (with the bumped fuser): ``` ERROR FUSE mount failed: fusermount: failed to open /dev/fuse: Permission denied ``` The error provenance shifts from the direct `DevFuse::open` path to `fusermount`, confirming the fallback is now taken. In a real unprivileged-Kubernetes setup where fusermount is proxied to a privileged host context (as SkyPilot does), this path succeeds end-to-end.
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`fuse_mount_sys` already falls back to fusermount on `mount(2)` EPERM, but returns a hard error when `DevFuse::open()` fails. This means unprivileged containers that lack `/dev/fuse` but have a (possibly proxied) fusermount binary never reach the fallback path.
This returns `Ok(None)` on `NotFound`/`PermissionDenied` from `DevFuse::open()` so the caller retries via fusermount, matching the `mount(2)` behavior.