We provide an implementation of the UNIX I/O interface for clients running Linux versions 2.4 (2.4.19 and later) and 2.6. This interface implements the traditional open, read, write, and close interface as well as providing the directory operations necessary for applications such as ls to work.
It is important to note that there is a difference between implementing the UNIX I/O API and implementing the POSIX semantics for this API. File systems exported via NFS (versions 2 and 3) do not exhibit many of the POSIX semantics, and even local file systems may not guarantee atomicity of writes that cross disk block boundaries. We also do not implement the full POSIX semantics. Here we will document aspects of the POSIX semantics that we do not implement.