How to set file and folder permission on Linux

You can set read, write and execute permissions on files and folders in Linux. You can apply these permissions to owner, group and those who are neither owner nor group member.

In the above screenshot you can see the highlighted section as drwxr-xr-x. The first character, d, simply implies that it's a directory where for files it should be -. The latter 9 characters are those that defines the permission for the folder.

The first 3 of the 9 characters are permissions for the user, the following 3 for the group and followed by for other users, represented by r (read), w (write), x (execute) and - (no permission). The assigned user and group for the directory is both root.

The above example's permission could then be defined as the followings;

Each category is can be represented by a single letter (u, g, o). Octal notation is a way of representing the permission in binary and to then total up the number. r-x for example is 1*(2^2) + 0*(2^1) + 1*(2^0), which results in 5. Here's a table for easier illustration;

With that out of the way, you can start configuring permission for your files and folders.

1. Get current permission of file.

   $ stat -c "%a : %A" /var/www/html/index.html 
   644 : -rw-r--r--

2. Add write permission for group for file.

   $ sudo chmod g+w /var/www/html/index.html
   [sudo] password for user:

3. Remove read permission to other for file.

   $ sudo chmod o-r /var/www/html/index.html

4. Set read and execute permission of user for file.

   $ sudo chmod u=rx /var/www/html/index.html

5. Check current permission of file.

   $ stat -c "%a : %A" /var/www/html/index.html 
   560 : -r-xrw----

6. Set all permission using octal and wildcard for all files and folders.

   $ sudo chmod 560 /var/www/html/*

7. Set all permission recursively for all files and folders..

   $ sudo chmod -R 560 /var/www/html/

8. Check current permission for all files and folders.

   $ sudo ls -l /var/www/html/
   total 20
   dr-xrw---- 2 root root  4096 Jan  24 09:58 css
   -r-xrw---- 1 root root 10918 Jan  23 19:57 index.html
   dr-xrw---- 2 root root  4096 Jan  24 09:57 js