chmod : Used to change the read, write and execute privileges of a file or directory for the owner, the group(s) they belong to, and all others (often called everyone)
chmod 777 somefile.txt : This would change the file somefile.txt to read/write/execute for the owner, the group belonged to, and everyone else (universal permissions)
Numeric and character values for the permissions are as follows:
r – 4 – Read permissions
w – 2 – Write permissions
x – 1 – Execute permissions
Adding these values together determines the privilege number
Example: chmod 755 somefile.txt
User: read (4) + write (2) + execute (1) = 7
Group: read (4) + execute (1) = 5
Everyone: read (4) + execute (1) = 5
Permissions can also be changed by single category using character representation
Example: chmod g+rw somefile.txt
Adds group permissions of read and write to the file called somefile.txt
Character values as follows:
u – User
g – Group
a – Everyone
r – Read
w – Write
x – Execute
+ – Add the values indicated
- – Remove the values indicated
chown: Change ownership to a specific user and/or group