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Tuesday, August 2, 2011

File Systems in Unix OS.

many of you have heard about File system. But many of the people do not know about the file system. I am going to explain a few things about Unix file system. 

What is an File system?

In Simple words the File system is to organize the data in the computer that handled by the Operating System. 

Many OS's are available in the market. I am going to explain a few things about the Unix OS.  In the olden days like 1980's file systems were either disk based in which all the files were held on a physical disk or were RAM based. In the RAM based file system, the file system will be survive only till the system was rebooted. In the last 15 years many pseudo file systems have introduced. 

The Unix File system is a collection of  files and directories. It has the following properties. 

It has a root directory (/) that contains other files and directories. Most disk-based filesystems will also contain a lost+found directory where orphaned files are stored when recovered following a system crash.

Each file or directory is uniquely identified by its name, the directory in which it resides, and a unique identifier, typically called an inode.

By convention, the root directory has an inode number of 2 and the lost+found directory has an inode number of 3. Inode numbers 0 and 1 are not used. File inode numbers can be seen by specifying the -i option to ls.

It is self contained. There are no dependencies between one file system and any other.  

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