files/directories/subvolumes inside it, but nothing in parent subvolumes.
Also every btrfs filesystem has a default subvolume as its initially top-level
-subvolume, whose subvolume id is 5(FS_TREE).
+subvolume, whose subvolume id is 5. (0 is also acceptable as an alias.)
A btrfs snapshot is much like a subvolume, but shares its data(and metadata)
with other subvolume/snapshot. Due to the capabilities of COW, modifications
EXIT STATUS
-----------
-*btrfs subvolume* returns a zero exit status if it succeeds. Non zero is
+*btrfs subvolume* returns a zero exit status if it succeeds. A non-zero value is
returned in case of failure.
AVAILABILITY