Filesystems
Each file volume (filesystem) has a type, determined by its disk layout or the network protocol used to access it.
ufs (ffs), lfs, nfs, rfs, cdfs, etc.
Filesystems are administered independently.
Modern systems also include “logical” pseudo-filesystems in the naming tree, accessible through the file syscalls.
procfs: the /proc filesystem allows access to process internals.
mfs: the memory file system is a memory-based scratch store.
Processes access filesystems through common system calls.