Page 461 - DCAP103_Principle of operating system

Principles of Operating Systems

Notes 14.6.8.4 NFS Version 4
Version 4 of the Network File System was designed to simplify certain operations from its
predecessor. In contrast to NSFv3 which is described above, NFSv4 is a stateful file system.
This permits open operations to be invoked on remote files, since the remote NFS server will
maintain all file system related structures, including the file pointer. Read operations then
need not include absolute read ranges, but can be incrementally applied from the previous file
pointer position. This results in both, use of shorter messages, and also in the ability to bundle
multiple NFSv3 operations in one network transaction. The stateful nature of NFSv4 makes
it easy to also integrate the variety of NFSv3 protocols described earlier in this section into
one coherent protocol. There is no need to support separate protocols for mounting, caching,
locking, or secure operations. NFSv4 also works better with both Linux (and UNIX in general)
and Windows file system semantics.

14.7 Security in Linux

Linux, as a clone of MINIX and UNIX, has been a multiuser system almost from the beginning.
This history means that security and control of information was built in very early on. In the
following sections, we will look at some of the security aspects of Linux.

Self Assessment

Fill in the blanks:
6. ....................... command is used to create Linux file system.
7. In the Linux process, the ....................... contains the machine instruction.
8. The kernel and memory map parts of main memory in Linux are ....................... in memory.

9. A ....................... file is one consisting of a sequence of numbered blocks.
10. ....................... contains information about the layout of the file system.

14.8 Summary

• The first version of Linux 0.01 was released in 1991. It was cross-developed on a MINIX
machine and borrowed numerous ideas from MINIX ranging from the structure of the
source tree to the layout of the file system.

• Linux is a multiprogramming system, so multiple independent processes may be running
at the same time.
• When the computer is start, the BIOS performs powers-ON self (POST) and initial device
process.
• The Linux memory model is straightforward to make programs portable and to make
it possible to implement Linux on machine with widely differing memory management
units.
• The I/O system in Linux is fairly straightforward.
• The most visible part of any operating system, including Linux is the file system.

• Security of Linux. The Linux as a clone of MINIX and UNIX has been a multiuser system
almost from the beginning.

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