How to debug FUSE filesystem when it is running in daemon mode?

Question

I am debugging a FUSE filesystem. It runs fine whenever I enable the -d or -f flag, but whenever I make it a daemon, it stops working (showing no files).

Is there a way for the daemon to print something to a log file? I have tried

-ologfile='./log'

but I just get an "unknown option" message.

Answer 1

The only way is to add a log function of your own would be in the code of this file system, using libfuse function fuse_set_log_func:

https://libfuse.github.io/doxygen/fuse__log_8h.html#af19307887778edec299c02c1e858addd

To debug the file system as it is, in some implicit way, would be to strace the file operations you are calling on it. for instance, strace ls /mnt/my_fuse will at least show you errors if some system call fails. It might give you a clue what fuse function is failing on the fuse side of this call.