Unix File Access
UNIX® is provides security to directory and the file system. For security reason a file or directory has assigned permissions to use them and every user in the UNIX system is assigned set of permission while creating user account. Before going to discuss the file permission, let’s discuss the user account types in the UNIX. There are three types of user accounts on a UNIX system that are root account, system account and normal user account. Root account: It is a super account in UNIX system and created when the Operating System installed. It has complete, unfettered control of the system and can run any commands without any restriction. This user account in UNIX system is treated as an administration. System accounts: System accounts are those accounts that are needed for a specific system operation or function of system-specific components. For emailing activity mail system accounts are created. These accounts can perform some specific function on system, and any modifications to them could adversely affect the system. User accounts: User accounts are those accounts that through which system interactive operations can be performed by normal users and groups of users. General users are typically assigned to these accounts and usually have limited access to critical system files and directories. All these accounts are managed by the system administrator (it is a root account). UNIX supports Group Account concept in which a number of user accounts can be combined with certain permissions and policies. Group account controls the file and directory handling and mange permissions to use these files. A group account must be created before the creation of user account and it must be added into a group account by using the groupadd UNIX command. In UNIX every file and directory has read, write and execution access modes. These read, write and execution permission is defined by the Owner or the system administrator. These permissions...
References: UNIX permissions help. Retrieved from http://www.zzee.com/solutions/unix-permissions.shtml
Unix - User Administration. Retrieved from http://www.tutorialspoint.com/unix/unix-user-administration.htm
File-System Interface. Retrieved from http://www.dia.unisa.it/professori/rescigno/SO/Silb_exerc/10-sol.pdf
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