ettom / dffs

About

dffs is a minimal FUSE-based pseudo-filesystem written in C, designed for educational and testing purposes. It exposes two special files, /used and /avail, that can be read from and written to in order to adjust the "used" and "available" space in the filesystem.

I wrote this mostly so I can have homepage display the space usage for filesystems that it doesn't have direct access to. I have it set up so a systemd timer periodically writes the usage of some other filesystem to the special files. I then make the dffs mountpoints available to the Docker container via a volume. It's set up roughly like this:

fs="z0"
mountpoint="/var/lib/homepage/dffs/$fs"
dffs -o fsname="dffs-$fs" "$mountpoint"
while :; do
    zfs get -o value -Hp used "$fs" > "$mountpoint/used"
    zfs get -o value -Hp avail "$fs" > "$mountpoint/avail"
    sleep 60
done

Build

make

or

nix-build -E 'with import <nixpkgs> {}; callPackage ./. {}'