Advanced File Permissions in Linux

Introduction

Linux is a powerful and adaptable operating system with numerous features that make it suitable for both personal and business use. File permissions are one of these features that is very important because they let you control who can access and change your files. We'll take a closer look at Linux's advanced file permissions in this article, focusing on some of the most important ideas and commands.

Setting File Permissions in Linux

Understanding Linux file permissions starts with knowing how to set them. The chmod command, which stands for "change mode," is used to accomplish this. Change the permissions of a file or directory with the chmod command, which lets you specify who can read, write, and execute the file.

You will need to specify the permissions for each user type using a combination of letters and numbers when setting the permissions for a file. Read, write, and execute are represented by the letters r, w, and x in this context. 7 stands for full access, while 6 stands for read and write, 5 stands for read and execute, 4 stands for read only, 3 stands for write and execute, 2 stands for write only, and 1 stands for execute only.

For example, The following command would be used to set the permissions for a file so that the owner has full access, the group has read and execute access, and no one else has access −

$ chmod 750 filename

You can also set permissions using octal notation. A series of three digits is used to represent the permissions granted to each user type in this way. The permissions granted to the owner are represented by the first digit, the permissions granted to the group by the second digit, and the permissions granted to everyone else by the third digit.

The -R option is used to recursively perform the action of chmod command for all of the directory's files and subdirectories.

Displaying File Permissions in Linux

After establishing a file's permissions, it is helpful to know how to display them. The “ls -l” command, which shows a list of files in a directory and their permissions, can be used to accomplish this.

For instance, the output of the “ls -l” command might look something like this −

drwxrwxr-x  2  john users 4096 Feb 2 10:20 Documents
-rwxrwxr-x  1  john users 8192 Feb 2 10:20 file.txt

In the example above, the first column displays the permissions for each file. The type of file is indicated by the first character, with d representing a directory and - representing a standard file. The permissions for each user type are represented by the following nine characters: r for read, w for write, and x for execute.

The group (users) has read and execute access to both the Documents directory and the file.txt file, whereas the owner (john) has full access to both.

Changing File Ownership in Linux

In Linux, every user and group owns every file and directory. The chown command lets you change who owns a file or directory. The chown command uses the following syntax −

$ chown [OPTION]... [OWNER][:[GROUP]] FILE...

For instance, the following command would be used to change user1's ownership of file.txt −

$ sudo chown user1 file.txt

Run the following command to change the owner of a directory named dir to user1 −

$ sudo chown -R user1 dir

The -R option is used to recursively change ownership for all of the directory's files and subdirectories.

Changing Group Ownership in Linux

In Linux, each directory and file is a member of a group as well. Using the chgrp command, you can change a file or directory's group ownership. The chgrp command uses the following syntax −

$ chgrp [OPTION]... GROUP FILE...

For instance, to assign group1 ownership to a file with the name file.txt, run the following command −

$ sudo chgrp group1 file.txt

Run the following command to change the group ownership of a directory named dir to group1 −

$ sudo chgrp -R group1 dir

The -R option is used to recursively change group ownership for all of the directory's files and subdirectories.

Conclusion

In conclusion, we have learned about Linux's advanced file permissions, including how to change ownership of files and directories, set permissions, and modify permissions. Working with Linux requires an understanding of file permissions, as does knowing how to effectively manage them. You can now work with file permissions in Linux with confidence by utilizing the information provided by this article.