Understanding File Permissions and Ownership

 

In Linux, every file is owned by a single user and a single group, and has its own access permissions. The basic Linux permissions model works by associating each system file with an owner and a group and assigning permission access rights for three different classes of users: The file owner, the group members, and others (everybody else)^.

File ownership can be changed using the chown and chgrp commands. Every file and directory in Linux has three kinds of owners: User, Group, and Other. User is the owner of the file. When you create a file, you become the owner of the file. The ownership can be changed as well, . Every user is part of a certain group(s). A group consists of several users and this is one way to manage users in a multi-user environment. Other can be considered as a big group with all the users on the system. Basically, anyone with access to the system belongs to this group .

Every file and directory in Linux has three permissions for all the three kinds of owners: Read, Write, and Execute. Understanding file permissions and ownership is crucial for a Linux user.

change file permissions linux

 

To change file permissions in Linux, you can use the chmod command. The basic syntax of the command is as follows:

chmod [permissions] [file]

Here, [permissions] are the permissions you want to assign to the file, and [file] is the name of the file whose permissions you want to change. The [permissions] parameter is a combination of three different types of permissions: read (r), write (w), and execute (x). Each permission is represented by a digit, where r is 4, w is 2, and x is 1. You can add these digits together to create a unique permission code for each user type (owner, group, and others). For example, if you want to give the owner read and write permissions, the group read permissions, and others no permissions, you would use the following command:

chmod 640 [file]

Here, 6 represents the owner’s permissions (4 for read and 2 for write), 4 represents the group’s permissions (4 for read), and 0 represents others’ permissions (no permissions).

You can also use the chown and chgrp commands to change the ownership of a file or directory. The basic syntax of the commands is as follows:

chown [user] [file]
chgrp [group] [file]

Here, [user] is the name of the user you want to assign ownership to, [group] is the name of the group you want to assign ownership to, and [file] is the name of the file or directory whose ownership you want to change.