Book Image

CentOS System Administration Essentials

Book Image

CentOS System Administration Essentials

Overview of this book

Table of Contents (18 chapters)
CentOS System Administration Essentials
About the Author
About the Reviewers

Special permissions

The permissions or mode of a file you we will be familiar with is Read, Write, and eXecute (RWX). These permissions can be set to the three objects:

  • User

  • Group

  • Others

The standard permissions are shown with their octal notation, should you want a quick revision exercise, as follows:

There is a fourth block of permissions that precedes user, group, and others. This block is for the special permissions; however, rather than representing RWX, the permissions comprise of:

  • The set user ID (SUID) bit

  • The set group ID (SGID) bit

  • The sticky bit

Using symbolic notations, these permissions can be added to file1, which acts as our axiom for the filename during the following demonstration:

$ chmod u+s file1 #adding the SUID Bit
$ chmod g+s file1 #adding the SGID Bit
$ chmod o+t file1 #adding the Sticky Bit

The SUID bit

The set user ID bit is used when a program needs to run using another user ID other than the user running the program. When set, the program runs with the permissions of the...