File permissions linux cheatsheet

A Linux file system is made up of users, groups and files. The files need the appropriate permissions so that users can work with them.

File permissions

In order to create, remove, update and delete files on your linux system. Files and folders need to have the correct permissions. Heres a list of some of the most common commands.

List users of the file system

less /etc/passwd

List all files and folders in current directory with file permissions and ownerships

ls -l

Change permissions of a single file or folder

chmod 755 filename,

Change all files and folder permissions

Recursively change all the files in the directory permissions to 755, and all file permissions to 644:

sudo find /var/www/html/ -type d -exec chmod 775 {} \;
sudo find /var/www/html/ -type f -exec chmod 664 {} \;

View the permission settings of a specific directory

ls -ld directory_name

View information on a file

This will output lots of file information but also permission information in octal format

• see mode in the output

stat filename

Return the numeric value of a directory

stat -c %a directory_name

See what groups a user belongs to

id -Gn user

Change file and folder ownership to the current logged in user Recursively

sudo chown -R $USER:www-data /var/www/html

How symbolic permissions map to numeric codes:

r (read) is 4
w (write) is 2
x (execute) is 1

So:

rwx (read, write, execute) is 7
r-x (read, execute) is 5
r-- (read only) is 4

For example, rwxr-xr-x corresponds to:

Owner: rwx = 7
Group: r-x = 5
Others: r-x = 5