Understanding and Using the chmod Command in Linux

The chmod command in Linux is used to change the permissions of a file or directory. Permissions control who can read, write, and execute a file or directory, and are important for maintaining the security of your system. In this article, we will explain when to use the chmod command and how to use it, with some examples.

When to Use chmod

You may need to use the chmod command if you want to change the permissions of a file or directory, for example, to give other users access to a file, or to restrict access to a sensitive file.

How to Use chmod

The basic syntax of the chmod command is as follows:

chmod [permissions] [file or directory]

The permissions argument is a combination of letters and numbers that specify the new permissions for the file or directory. The letters “r”, “w”, and “x” represent read, write, and execute permissions, respectively. The numbers “4”, “2”, and “1” represent the same permissions, respectively.

For example, to give a user read and execute permissions for a file named “example.txt”, you would use the following command:

chmod +rx example.txt

To remove execute permissions for a directory named “example”, you would use the following command:

chmod -x example

You can also use the numbers “4”, “2”, and “1” to specify permissions, rather than the letters “r”, “w”, and “x”. For example, to give a user read and execute permissions, you would use the number “5”, which is the sum of “4” (read) and “1” (execute).

To give read, write, and execute permissions to all users, you would use the number “7”, which is the sum of “4” (read), “2” (write), and “1” (execute).

Examples

1. Give read and write permissions to all users for a file named “example.txt”

2. Remove execute permissions from a directory named “example” for the owner

3. Give read, write and execute permissions to owner and read and execute permissions to group and other users for a file named “example.txt”

In conclusion, chmod command is a powerful tool in Linux that allows you to change the permissions of files and directories. By understanding when to use it and how to use it, you can maintain the security of your system and give other users access to the files they need.

See our list of 75 Linux commands you should know about.