What are file permissions ? Linux File Permissions Explained

What are file permissions ? Linux File Permissions Explained

Linux file permissions are a powerful tool that allows you to control who can access and manipulate files on your system. Understanding how to use file permissions is essential for anyone who wants to work with Linux, whether you’re a beginner or an experienced user. In this blog post, we’ll take a closer look at what file permissions are, how they work, and how to use them to keep your files and data secure.

What are File Permissions?

When you create a file or directory in Linux, the system assigns a set of permissions to it. These permissions determine who can read, write, and execute the file, and they’re an important part of the Linux security model. Every file and directory on a Linux system has three sets of permissions: user, group, and others.

User permissions determine what the owner of the file can do with it. Group permissions determine what members of the file’s group can do with it. And others permissions determine what all other users can do with it. Each set of permissions can be either read (r), write (w), or execute (x).

How do File Permissions work?

File permissions in Linux are represented by a string of letters and symbols. The string is divided into three parts, each representing the permissions for the user, group, and others. For example, the string “rwxr-xr-x” means that the user has read, write, and execute permissions, the group has read and execute permissions, and others have read and execute permissions.

The first character in the string represents the user’s permissions, the second character represents the group’s permissions, and the third character represents the others’ permissions. The remaining characters in the string are used to indicate the file type and special permissions.

To view the permissions on a file or directory, you can use the ls -l command in the terminal. This command will show you a list of all the files and directories in the current directory, along with their permissions, ownership, and timestamps.

How to Change File Permissions?

Changing file permissions is done using the chmod command. The chmod command allows you to change the permissions on a file or directory by specifying the new permissions in either octal or symbolic form.

The octal form of chmod uses a three-digit number to represent the permissions. The first digit represents the user’s permissions, the second digit represents the group’s permissions, and the third digit represents the others’ permissions. Each digit is a combination of the numbers 4, 2, and 1, which represent the read, write, and execute permissions respectively.

The symbolic form of chmod uses a combination of letters and symbols to represent the permissions. The letters u, g, and o represent the user, group, and others permissions respectively. The symbols + and – are used to add or remove permissions, and the symbol = is used to set the permissions to a specific value.

For example, to give the user read and write permissions, and the group and others read-only permissions on a file, you would use the command:

chmod u+rw,g+r,o+r file.txt

Alternatively, you can use the octal form of chmod, which is 755, to achieve the same result.

chmod 755 file.txt

Commonly used file permissions

Some common examples of file permissions are listed below:

1. rwxrwxrwx: This set of permissions gives the user, group, and others full read, write, and execute permissions. This is often used for scripts or programs that need to be executed by anyone.
2. rw-rw-rw-: This set of permissions gives the user, group, and others full read and write permissions, but no execute permissions. This is often used for files that need to be read and written by anyone, but not executed.
3. rwxr-xr-x: This set of permissions gives the user full read, write, and execute permissions, while the group and others have read and execute permissions only. This is often used for files that need to be executed by the user, but only read by others.
4. rw-r--r--: This set of permissions gives the user full read and write permissions, while the group and others have read-only permissions. This is often used for files that need to be read and written by the user, but only read by others.
5. rwx------: This set of permissions gives the user full read, write, and execute permissions, while the group and others have no permissions. This is often used for sensitive files that should only be accessible by the user.

Conclusion

File permissions are a fundamental aspect of the Linux operating system. They allow you to control who can access and manipulate files on your system, and are an important part of the Linux security model. Understanding how to use file permissions is essential for anyone who wants to work with Linux