Understanding Basics of FileSystem
Understanding Basics of File-system
Lets try to understand what is a FileSystem and whats the need for one .
Examples of a FileSystem are ext2, ext3, ext4, XFS, NTFS, Fat32, Fat16
Lets begin by examining Human reading and writing skills .
Page1 Honesty is the best policy. You should Always be honest.
Lets examine .
- How did you figure out the words (Honesty, best, Always )
- How did you figure out how many lines are there
- How did u figure out the alphabets . H, O, N, E, S, T.
Human brain has been taught the semantics of reading and writing . The semantics goes by
- Group of alphabet together with space as delimiter is a word .
- A new Line is how we discover the start of a line .
- To read a word one needs to read from left to Right(HONESTY) and not vice Versa(YTSENOH)
- To read a line we read from left to right and not vice versa.
- Each alphabet has been associated with a specific sound and a specific way of writing it. How you pronounce “a” differs from “h” and same for writing it.
Lets try to understand from CPU perspective how does the world look like .
- Everything is represented as 0 and 1 .
- 0 and 1 themselves are state representation. can be represented as Voltage +10v => 1 , +5v=>0
- CPU sees no difference at all between different kind of files.
- CPU has no idea of how to read a word , line , sentence paragraph
- All it knows is Binary form of OPCODE PARAM PARAM
Lets try to understand from Hard-disk (Storage ) perspective how does the world look like
- There are two state it is aware of Magnetized and demagnetized
- The state can be translated to 0 and 1 by some external translator like Drive of the hard-disk.
- Hard disk is aware of track and sectors.
- It has no clue of what is a file a directory.
- It has no clue what is a text file , a c file , a binary file , a java file , a php file .
- It just magnetizes , demagnetize tracks and sectors based on the request made by the driver.
Lets try to understand from Operating System (OS ) perspective how does the world look like
- Operating system interacts with CPU, Hard-disk , Humans and all other resources.
- Operating System takes care of saving a file and retrieving back the info of the file in the same format.
- Operating System understand which application to open for which specific type of file.
- Operating system needs to provide humans view of file and directories
- Operating system needs to interact with CPU in terms of 0 and 1 .
- Operating system Provides ASCII translation
The catch is Operating System can be shutdown and still it needs to retrieve all info saved in the hard-disk And OS needs to provide the same view of File and directories as it was before shutdown .
Here comes the part where OS maintains the semantics just like Humans to differentiate file and directories, The semantics in detail cover everything
- How to distinguish file from a directory
- How to differentiate where a file starts and where it ends on hard-disk.
- Just realize its not a human but some code with some logic which can understand the boundaries .
- From hard-disk perspective OS is just getting back a stream of 0 an1 (demagnetized , magnetized)
- Along with actual file some meta info is also being saved this constitutes the data of the File system
FileSystem logic is also extended to maintain a in memory fileSystem known as /proc fileSystem in linux.
Linux Provides a variety of commands to explore and work on file system
|ls||list content inside a directory|
|vim fileName||create a file|
|df -hk||usage of directories|
|lsblk||In detail info of all Hard-disk attached|
|iostat -d -x 5||Live I/O info of the hard-disk|