Key Positions

Laboratory work № 2

Work with File System

Goal of work

1.1 To study structure of file system OC UNIX, rights for file access, attributes and flags.

1.2 To study ways of specifying attributes, flags.

Key Positions

2.1 Structure of the file system of UNIX
UNIX operating system differs from most systems because it is a file orientated. UNIX developers have decided that the operating system will be much easier if all its elements are seen as files. Disks, drives, terminals, modems, network connections, etc. - All of them are considered as files in UNIX. In some recent versions of UNIX (for example System V Release 4), even processes are files.
Therefore, to understand UNIX, you need to understand what is file. File is a chain of bytes of arbitrary length. There are no system constraints for the structure of the file does not exist. In UNIX there are only a few special types of files (for tracking the number of disks and other purposes). The structure of the files is programs that use them, but not the operating system UNIX (many binaries – i.e., program-start with a magic number. This is a special two-byte sequence that tells the kernel how to execute the file). Headers files are also determined by the application, which is working with them, and not the file system UNIX.
UNIX file system has a tree (hierarchical) structure (Fig. 5).
All files are in a UNIX shared to directories. Catalog - this is nothing like a file a special form, which lists the other files. This catalog may contain any number of files, but in terms of speed, number of files per directory should not exceed 100. The catalog can include other catalogs. At the top of the “tree” is the catalog which is called the root and has a special name - / (pronounced "slash", but never recorded in the form of the word).

Figure 5. File system UNIX tree

In UNIX «point of reference" is a ready-made, large enough file system tree. When you log on you find yourself somewhere in the lower her part of the tree in the directory created for your system administrator. This directory, i.e. area of file system, that belongs to you personally, and stores your files, called the initial directory.

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