File permissions

chmod
You can change file permissions with:

Numbers are obtained in the following way:
 * [u] is the number for user permissions
 * [g] is the number for group permissions
 * [o] is the number for other users permissions
 * 7 = 4 + 2 + 1 (read/write/execute)
 * 6 = 4 + 2 (read/write)
 * 5 = 4 + 1 (read/execute)
 * 4 = 4 (read)
 * 3 = 2 + 1 (write/execute)
 * 2 = 2 (write)
 * 1 = 1 (execute)

chown
You can change owner and group of file with:

You can change owner of folder and files inside recursively with:

gpasswd
You can add user to group with:

You can remove user from group with: