when mounting a fuse fs by fstab on can write:
/nix/store/sdlflj/bin/somefuseexe#argument /mountpoint fuse setuid=someuser
mount is run by root, and setuid is a way to tell mount.fuse to run
somefuseexe as someuser instead. Under the hood, mount.fuse uses su.
The problem is that mount is run by systemd in a seemingly very empty
environment not containing /run/current-system/sw/bin nor
/run/wrappers/bin in $PATH, so mount fails with "su command not found".
We now patch the command to run su with an absolute path.
man mount.fuse3 indicates that this option is reserved to root (or with
enough capabilities) so not using
/run/wrappers/bin/su is thus correct. It has the very small advantage of
possibly working on non nixos.
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