Reserved space includes: - inodes space in use (2 blocks per) - about 5.2% of the space The 5.2% reserved space was computed empirically when working on a previous EXT4 image builder. It seems to stabilize around 5% even for much larger filesystems.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at https://nixos.org/nixos and in the manual in doc/manual.