File Systems FAT & NTFS and NTFS Permissions by MAZHAR IQBAL BUTT.2

The methods of collection of files anddata file management structures thatan operating system uses to keeptrack of files on a physical disk orlogical partition. This part of theoperating system includes the way ofNaming, Storing, Organizing,Cataloguing and Retrieval of files ondisk. It handles access to input &output devices and data transfers.

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A file system refers to the logicalorganization of files, specifiesconventions for naming files, forstoring data in files, and forspecifying locations of files.

A File System translates the physical(sector) view of a disc into a logical(files, directories) structure, whichhelps both computers and userslocate files.

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A file system may be "flat" (nodirectories) or hierarchical (withdirectories and subdirectories).

Some file systems are built-incomponents of the operating system,while others are installable andinteract smoothly with the operatingsystem but provide more features,such as backup procedures and fileprotection.

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Some of the common file systems are:FAT (FAT16/FAT32) and NTFS on WindowsSystems and UFS/JFS on Unix Systems, S51K,ext2, Andrew File System (AFS), CommonInternet File System (CIFS), distributed filesystem (DFS), Fast File System (FFS),Hierarchical File System (HFS) for AppleMacintosh, Institutional File System (IFS),Network File System (NFS), EXTFS for Linux,HPFS (High Performance File System ) forOS/2, ISO 9660 for CDROMs and ISO 13346for DVDs, UDF (Universal Disk Format) for bigcapacity DVD RAM Disks

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File System Format

When installing anOperating System, thehard drive must first beformatted with a filesystem.

Windows uses two mainformats FAT32 andNTFS.

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FAT stands for File Allocation Tableand became available with Windows95 and is used for DOS, Windows95, 98, and ME. It can support largehard disk sizes of up to twoterabytes.

NTFS stands for New TechnologyFile System and has been used inWindows NT, 2000 & XP.

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"NTFS has features to improvereliability, such as transaction logsto help recover from disk failures.

To control access to files, you canset permissions for directoriesand/or individual files.

NTFS files are not accessible fromother operating systems such asDOS.“

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It is easier to protect files andrecover them after a failure, but theformatting cannot be read onprevious versions of Windows.

However, systems using the NTFSfile system can read disks usingFAT32.

Also, Windows NT, 2000, and XP canbe installed on disks that areformatted with FAT32.

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File Name & File Type

MS-DOS uses 8 characters file name, adot, then a 3 characters extension thatdenotes the type of file and are not case-sensitive.

UNIX Filenames can be up to 254characters long and are case-sensitive.

Windows Filenames can be up to 255characters long and are not case-sensitive.

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Operating System Functionality ofFile SystemThe hard disk is comprised of a largenumber of sequentially numberedsectors. As files are created, free sectorsare allocated to hold the file contents andmarked as allocated.To keep track of the sectors and whetherthey are allocated or free, and to whichfile they belong, the operating systemmaintains a number of tables.

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File Allocation Table (FAT) is a file

system (like a Table) that was

developed for MS-DOS to locate files

on a disk.

Due to fragmentation, a file may be

divided into many sections that are

scattered around the disk. The FAT

keeps track of all these pieces.

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FAT12This is initial version of FAT for floppy diskswith many limitations: no support forhierarchical directories and the disk size limitedto 32MB.FAT16The partition size reached at 2 gigabytes.VFAT (Virtual FAT)It is supported by Windows 95 and above andWindows NT 3.5 and above. It allows file anddirectory names up to 255 characters inlength.

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FAT32To increase drive sizes in the rangeof 2 terabytes. The maximumpossible file size for a FAT32 volumeis 4 GB minus 1 byte (232-1 bytes).FAT32 has the ability to relocate theroot directory and use the backupcopy of the FAT instead of thedefault copy.

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The Windows NT FileSystem (NTFS) providesperformance, reliability,and compatibility notfound in the FAT filesystem, whereasadvanced operationssuch as file-systemrecovery on very largehard disks.

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After formatting a volume with the NTFSfile system results in the creation ofseveral system files and the Master FileTable (MFT).

MFT contains information about all thefiles and folders on the NTFS volume. Itis the first file on an NTFS volume. TheNTFS file system also supports dataaccess control and ownership privilegesthat are important for the integrity ofcritical data.

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NTFS files and folders can have

permissions assigned whether they

are shared or not. NTFS is the only

file system on Windows NT that

allows you to assign permissions to

individual files.

The NTFS file system has a simple

but very powerful design.

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Everything on the volume is a fileand everything in a file is anattribute, from the data attribute, tothe security attribute, to the filename attribute. Every sector on anNTFS volume that is allocatedbelongs to any file.The file system metadata(information that describes the filesystem itself) is part of a file.

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Converting to NTFS Using the SETUPProgram

It begins by checking the existing file systemand gives the choice of converting to NTFS.

Converting to NTFS Using CONVERT.EXE

By using Convert.exe from the commandprompt.

Open Command Prompt. In the commandprompt window, type: convert drive_letter:/fs:ntfs

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A permission is a rule associated with anobject to regulate which users can gainaccess to that object and in whatmanner.NFTS permissions cover• NTFS file and folder permissions• Access Control Lists (ACL)• Using NTFS permissions• Planning NTFS permission• Using special access permission• COPYING/MOVING data• Troubleshooting permission problems

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Different kinds of permissions can beassigned to files and folders and theirusage.Permissions can be used only on NTFSformatted partitions or volumes, sothese are referred to as NTFSpermissions.Administrators, the user that owns thefiles or folders, and all other users orgroups that have the Full Controlpermission to those file and folders canset/reset these permissions.

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Default NTFS permissions are Full Control toeveryone.NTFS File Permissions are used to control theaccess that a user, group or application has tofiles.

To change the permission set on a file, takeownership of the file, and perform actions permittedby all of the other NTFS file permissions.

Full Control

To modify/delete a file.Modify

To run and execute the application.Read & Execute

To overwrite the file, change its attributes, view itsownership, and view the permissions set.

Write

To read the file, view its attributes, ownership, andpermissions set.

Read

Allowed AccessNTFS FilePermission

NTFS FILE PERMISSIONS

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NTFS Folder Permissions allowwhat access is granted to a folderand the files and subfolders withinthat folder.These permissions can be assignedto a user or group.The only major difference betweenNTFS file and folder permissions isthe List Folder Contents NTFS folderpermission.

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To change permissions on the folder, takeownership of it, and perform all activities includedin all other permissions.

Full Control

To delete the folder.Modify

To navigate through all files and subfolders.Read &Execute

To view the files and subfolders contained withinthe folder.

List FolderContents

To create new files and folders within the parentfolder as well as view folder ownership andpermissions and change the folder attributes.

Write

To view the files, folders & subfolders of the parentfolder, their ownership, permissions, and attributesof that folder.

Read

Allowed AccessNTFS FilePermission

NTFS FOLDER PERMISSIONS

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When a user tried to access a file orfolder, the operating system look at theuser's ACL (Access Control List) anddetermine whether the user was allowedaccess. The ACL was created only after asuccessful logon.

Then ACL checks for an ACE (AccessControl Entry) for that user account. TheACE will indicate what permissions areallowed for that user account.

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Right click on File/FolderClick Properties

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Select Security TabClick Advanced button tochange the defaultpermissions.

(By default Folders & Filesinherit permissions fromparents. If you want changepermissions you have toremove Inheritance.)

ACL(Access Control List)

ACE(Access Control Entry)

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Removebutton isdisabledbecausepermissionsare inherited.

Un-check the Inherit from parent thepermission entries that apply to child objects.

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Click Copy

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Remove button is enabled, you canchange default permissions now.

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Remove all usersTo add user for which you will configurepermission Click Add

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Type the name of user or clickAdvanced button to look formore users.

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Select appropriatecheck boxes in frontof Permissions.If you want to applythese permissions toall subfoldersSelect Apply thesepermissions toobjects check-box.

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Add & Apply anyfurther users &permissions ifrequired.

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You can alsoapplyPermissions onsubfolders onAdvancedSecuritySettings Dialogbox

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Click YesIt will applies permission to allfiles & folders in that folder.

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Select Sharing TabOpen Properties ofFolder which youwant to Share

SHARING FOLDERS

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Click on Share thisFolder, & typename of share.

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By default onlyRead permission isapplies to Everyonegroup.If you want toenable users towrite files in thisfolder, Changepermissions shouldassigned.