The lufsd daemon

As soon as lufsd starts the execution, it loads a well-known shared library (its name is derived from file system name, i.e. $\texttt{liblufs-pkgfs.so}$), that holds rewritten system calls for the specific file system. Upon successful opening, the server will try to resolve some symbols. PackageFS symbols are described later in section 5.3.1, where their implementation will be explained. Meaningful functions they include are:

• $\texttt{init}$ : it initializes the file system reading configuration options, and setting the cache to be used. Then it allocates and returns a structure to hold all of its information;
• $\texttt{mount}$ : it is called to carry out PackageFS mounting;
• $\texttt{umount}$ and $\texttt{free}$ routines that are invoked at unmount time.
• Other functions, as the reader can imagine, override regular system calls shown in chapter 3. PackageFS mostly relies on implementation of these functions.

In the end, it has to be said that lufsd provides a cache which primary goal is to speed up access to network file systems. It saves last visited directories and their entries in a hash table and keeps them valid for a configurable amount of time.