UNIX Filesystems: Evolution, Design, and Implementation

Other Pseudo Filesystems

There are a large number of different pseudo filesystems available. The following sections highlight some of the filesystems available.

The UnixWare Processor Filesystem

With the advent of multiprocessor-based systems, the UnixWare team introduced a new filesystem type called the Processor Filesystem [NADK92]. Typically mounted on the /system/processor directory, the filesystem shows one file per processor in the system. Each file contains information such as whether the processor is online, the type and speed of the processor, its cache size, and a list of device drivers that are bound to the processor (will run on that processor only).

The filesystem provided very basic information but detailed enough to get a quick understanding of the machine configuration and whether all CPUs were running as expected. A write-only control file also allowed the administrator to set CPUs online or offline.

The Translucent Filesystem

The Translucent Filesystem (TFS) [HEND90] was developed to meet the needs of software development within Sun Microsystems but was also shipped as part of the base Solaris operating system.

The goal was to facilitate sharing of a set of files without duplication but to allow individuals to modify files where necessary. Thus, the TFS filesystem is mounted on top of another filesystem which has been mounted read only.

It is possible to modify files in the top layer only. To achieve this, a copy on write mechanism is employed such that files ...