Книга: Distributed operating systems

9.1.6. The UNIX Subsystem

9.1.6. The UNIX Subsystem

Since Chorus is now a commercial product, it must give the masses what they want, and what they want (at least in the high-end workstation world) is compatibility with UNIX. Chorus accomplishes this goal by providing a standard subsystem, called MiX, that is compatible with System V. the compatibility is both at the source level (i.e., unix source programs can be compiled and run on Chorus) and at the binary level (i.e., executable programs compiled on a true UNIX system for the same architecture run without modification on Chorus). An earlier version of MiX (3.2) was compatible with 4.2 BSD, but we will not discuss that version further in this chapter.

MiX is also compatible with UNIX in other ways. For example, the file system is compatible, so Chorus can read a UNIX disk. Furthermore, the Chorus device drivers are interface compatible with the UNIX ones, so if UNIX device drivers exist for a device machine, they can be ported to Chorus with relatively little work.

The implementation of the MiX subsystem is more modular than UNIX. It consists of four processes, one for process management, one for file management, one for device management, and one for streams and interprocess communication. These processes do not share any variables or other memory, and communicate exclusively by remote procedure call. Later in this chapter we will describe in detail how they work.

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