Linux permissions and file ownership

Linux permissions and file ownership are an important part of the Linux file system. They determine which users or groups can access, modify or execute a file or directory.

There are three types of permissions:

• Read (r)
• Write (w)
• Execute (x)

Each permission can be assigned to three types of users:

• Owner (user who created the file/directory)
• Group (users belonging to a specific group)
• Others (all other users)

File ownership, on the other hand, determines which user or group owns a file or directory.

Here are some examples of how to work with Linux permissions and file ownership:

• Displaying permissions and ownership To view the permissions and ownership of a file or directory, use the ls -l command. The output will show the permissions and ownership in the following format:

In this example, the file myfile.txt is owned by username and belongs to the groupname group. The permissions are set to read and write for the owner, and read-only for group members and others.

• Changing file permissions To change the permissions of a file or directory, use the chmod command. For example, to give the owner and group write permissions and others no permissions to a file, you can use the following command:

In this example, the first number (6) sets the permissions for the owner, the second number (6) sets the permissions for the group, and the third number (0) sets the permissions for others. The numbers correspond to the permission types (4 for read, 2 for write, 1 for execute) and can be added together to set multiple permissions.

• Changing file ownership To change the ownership of a file or directory, use the chown command. For example, to change the owner of a file to newuser, you can use the following command:

In this example, the file myfile.txt will now be owned by newuser.

• Changing group ownership To change the group ownership of a file or directory, use the chgrp command. For example, to change the group of a file to newgroup, you can use the following command:

In this example, the file myfile.txt will now belong to the newgroup group.

These are just a few examples of how to work with Linux permissions and file ownership. It's important to understand how these concepts work and how to properly manage them, in order to maintain the security and integrity of your Linux system.