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Good Morning. Session -5. Recap…. Understanding Distributions Major Distribution. Session Objectives. Understanding File System File System Used Windows (FAT, FAT32,NTFS) Linux (ext2,ext3) File / Directory Structure of Red Hat LINUX Linux FHS vs Windows File System. File System.

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Good Morning

Session -5

  • Understanding Distributions
  • Major Distribution
Session Objectives
  • Understanding File System
  • File System Used
    • Windows (FAT, FAT32,NTFS)
    • Linux (ext2,ext3)
  • File / Directory Structure of Red Hat LINUX
  • Linux FHS vs Windows File System
File System

File systems organize the data stored on computer hard drives, keeping track of the physical locations of all data elements on disk while allowing users to quickly and reliably retrieve files when needed

The file system acts as a digital index that lets a computer instantly find a specific file, regardless of the size or configuration of the storage drive or where the data bytes associated with the file sit on the drive's storage platters.

The file system is based on management of clusters, the smallest disk unit that the operating system is able to manage.

A cluster consists of one or more sectors, so the larger the cluster size, the fewer entities the operating system will have to manage.

  • File systems have come a long way since MS-DOS and early versions of Windows. Those operating systems organized files under the FAT file system
    • it represents logical areas of the disk in allocation units called clusters, and maps the locations of file data to those areas using a file allocation table (FAT).
    • FAT is also called FAT16 because it uses a 16-bit address space for tracking files and clusters.
    • FAT clusters vary with the size of the disk.
    • FAT's 16-bit address space can support up to 65,536 clusters (216).
    • With a 65MB disk, cluster sizes were just 1KB in size, but they ballooned as disks emerged that were able to hold gigabytes of data. And since only a single file can be written to a cluster, this created inefficiencies that ended up wasting as much as 50% of available space on a 2GB disk drive
  • FAT32, which debuted with Windows 95 , introduced a 32-bit address space.
  • By increasing the size of the file allocation table, it could support more clusters that were smaller in size on large disk drives, reducing the potential for wasted drive space.
  • Another FAT32 innovation was that it could handle file names with up to 255 characters, whereas FAT could only handle names with up to eight characters.Users could finally create long file names to better describe the contents.
  • The advent of FAT32 extended the maximum addressable volume size from 2GB to 2TB and improved reliability by allowing the system to switch to a copy of the file allocation table if the default copy should become damaged.
  • The next development in Windows file systems was the New Technology File System (NTFS), introduced with Windows NT (which also supported FAT32).
  • With a 64-bit address space and the ability to vary cluster size independently of the disk drive size, NTFS virtually eliminated the cluster size limitation problem.
  • It also brought other benefits, including file and directory security attributes, file encryption and support for storage volumes of up to 16TB and 232 clusters.
  • NTFS replaced the familiar file allocation table format with the Master File Table (MFT), which holds more information about files than did FAT. The MFT references all files and directories on the disk drive, including associated metadata such as security settings.
  • The NTFS also introduced a high level of fault tolerance. It logs disk operation activity prior to committing the transaction. If the system crashes during an update, it can examine the log file and restore the data. When read or write errors occur during normal operation, NTFS automatically identifies and blocks out the bad clusters and copies the data to a new location. Finally, NTFS creates a mirror of the MFT and can revert to the mirror should the original fail.
Ext2 & Ext3
  • The Linux file system, called Extended File System 2, evolved to rectify limitations of Linux's original file system, Ext, which the operating system inherited from its Minix predecessor. Under the Minix file system, the maximum file system size was restricted to 64MB and file names to 14 characters.
  • Ext supported 2GB file systems and 255-character file names but suffered from some performance limitations. Ext2 supports 4TB file systems and 255 character file names and remedies those problems.
  • The Ext2 architecture uses a data structure called identification nodes (inodes) to refer to and locate files and associated data. The inode table includes the file type, size, access rights, pointers to associated data blocks and other attributes. The file system organizes disk space into groups of blocks, which contain both inode information and associated data blocks.
  • The Linux kernel uses the Virtual File System layer, which interacts with the file system to perform disk I/O. This gives Linux the ability to support multiple file systems, including DOS, FAT16 and FAT32 (which it supports as a native file system).               
File System Specs

*4GB under Windows NT

Red Hat is committed to the Filesystem Hierarchy Standard (FHS), a collaborative document that defines the names and locations of many files and directories

An operating system's file system structure is its most basic level of organization. Almost all of the ways an operating system interacts with its users, applications, and security model are dependent upon the way it stores its files on a storage device. It is crucial for a variety of reasons that users, as well as programs, be able to refer to a common guideline to know where to read and write files.

The major advantages of using the FHS are the predictability and consistency of file locations. Instead of an administrator searching the entire filesystem for a particular type of file, he can know that it will be in one of a few established locations.

FHS provides sepcific requirements on placement of files in the directory structure. The placement of files are based upon the type of information they contain.

For more information on the FHS, refer to

A file system can be seen in terms of two different logical categories of files:

Shareable vs. unshareable files — Shareable files are those that can be accessed by various hosts; unshareable files are not available to any other hosts.

Variable vs. static files — Variable files can change at any time without any intervention; static files, such as read-only documentation and binaries, do not change without an action from the system administrator or an agent that the system administrator has placed in motion to accomplish that task


The / (Root) Directory

The root partition/volume is identified by a forward slash (/). All other directories are attached (mounted) to this parent directory. It is equivalent to the system drive (C:\ ) in Windows.

The /bin Directory

This directory contains all the commands that will be used by the user i.e. common Linux user commands. It can’t contain any subdirectory

The /dev Directory

The /dev directory contains file system entries that represent devices that are attached to the system. These files are essential for the system to function properly

The /mnt Directory

The /mnt directory is for temporarily mounted file systems, such as CD-ROMs , floppy disks or usb drives.

The /lib Directory

The /lib directory should contain only those libraries that are needed to execute the binaries in /bin and /sbin. These shared library images are particularly important for booting the system and executing commands within the root file system

The /etc Directory

The /etc directory is reserved for configuration files that are local to your machine. No binaries are to be put in /etc. Any binaries that were formerly put in /etc should now go into /sbin or possibly /bin.

The X11 and skel directories are subdirectories of the /etc directory. The X11 directory is for X11 configuration files such as XF86Config. The skel directory is for "skeleton" user files, which are used to populate a home directory when a user is first created.

The /usr Directory

The /usr directory is for files that can be shared across a whole site. The /usr directory usually has its own partition, and it should be mountable read-only.

The /root Directory

This is the home directory of the user “root”.

The /home Directory

It contains the directory of users on the system. The subdirectory will be named for the user to whom it belong.

The /boot Directory

It contains the kernel of the system and also contains all the programmes required for booting like Boot Loader.

The /var Directory

It contains variable information such as system log and print queues.

The /proc Directory

Within the /proc/ directory, one can find a wealth of information about the system hardware and any processes currently running. In addition, some of the files within the /proc/ directory tree can be manipulated by users and applications to communicate configuration changes to the kernel.

Linux File Systems Versus Windows-Based File Systems

In MS-DOS and Windows file systems, drive letters represent different storage devices (forexample, A: is a floppy drive and C: is a hard disk). In Linux, all storage devices are fit into the file system hierarchy. So, the fact that all of /usr may be on a separate hard disk or that /mnt/rem1 is a file system from another computer is invisible to the user.

Slashes, rather than backslashes, are used to separate directory names in Linux. So,C:\home\chris in an MS system is /home/chris in a Linux system.

Filenames almost always have suffixes in DOS (such as .txt for text files or .doc for word processingfiles). Although at times you can use that convention in Linux, three-character suffixes have no required meaning in Linux. They can be useful for identifying a file type.

Many Linux applications and desktop environments use file suffixes to determine the contents of a file. In Linux, however, DOS command extensions such as .com, .exe, and .bat don’t necessarily signify an executable (permission flags make Linux files executable).

Every file and directory in a Linux system has permissions and ownership associated with it. Security varies among Microsoft systems. Because DOS and MS Windows began as single-user systems, file ownership was not built into those systems when they were designed. Later releases added features such as file and folder attributes to address this problem.