ABSTRACT
The chapter shows the protection and security mechanisms that Linux provides. It describes the types of users of a Linux file, how a user can set and change permissions for a file. The chapter discusses the basic operations that can be performed on a Linux file, how a user can determine access privileges for a file, special protection bits, set-user-ID, set-group-ID, and sticky bit, and also describes their purpose. The Linux commands mcrypt and openssl can be used to encrypt and decrypt files. Access permissions for files can be viewed by using the ls -l command. When used with directories, this command displays attributes for all the files in the directories. The ls -ld command can be used to view access permissions for directories. The owner of a file can change access privileges on it by using the chmod command.
