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Peter Reiher<br />

University of California<br />

35.1 Definitions and Importance<br />

© 2002 by CRC Press LLC<br />

35<br />

Distributed Operating<br />

Systems<br />

35.1 Definitions and Importance<br />

35.2 Why Are Distributed Operating Systems<br />

Hard to Build?<br />

35.3 Components of Distributed Operating Systems<br />

File Systems • Interprocess Communications<br />

Services • Naming Services • Recovery, Reliability, and<br />

Fault Tolerance Services • Process Migration • Security<br />

Services<br />

35.4 Sample Distributed Operating Systems<br />

Locus • Amoeba • Plan 9<br />

35.5 Recent Research in Distributed Operating Systems<br />

Distributed File Systems • Networks of<br />

Workstations • Distributed Systems for Ubiquitous<br />

Computing • Security in Distributed Operating Systems<br />

35.6 Resources for Studying Distributed<br />

Operating Systems<br />

A distributed operating system is software that runs on several machines whose purpose is to provide a<br />

useful set of services, typically to make the collection of machines behave more like a single machine.<br />

The distributed operating system plays the same role in making the collective resources of the machines<br />

usable that a typical single-machine operating system plays in making that machine’s resources more<br />

usable.<br />

Distributed operating systems are usually viewed as running cooperatively on all machines whose<br />

resources they control. These machines might be capable of independent operation, or they might be<br />

usable merely as resources in the distributed system. Unlike parallel operating systems, a distributed<br />

operating system typically runs on loosely coupled hardware. Parallel operating systems tend to focus on<br />

making all available resources usable by a single large task, while distributed operating systems focus on<br />

making the collection of resources usable by a set of loosely cooperating users. Network operating systems<br />

are sometimes regarded as systems that attempt merely to make the network connecting machines more<br />

usable, without regard for some of the larger problems of building effective distributed systems. The distinctions<br />

between parallel, distributed, and network operating systems are somewhat arbitrary, because all<br />

must handle similar problems.<br />

Distributed operating systems are not in common use today. Altghough many interesting research systems<br />

have been built since the 1970s, and some systems have been in use for many years, they have not displaced<br />

more traditional operating systems designed primarily to support single machines; however, some of<br />

the components originally built for distributed operating systems have become commonplace in today’s

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