Mastering Linux File Permissions: A Simple Guide to Numbers and Letters

A simple way to understand Linux file permissions is to use numbers and letters. Here’s a quick guide:

Numeric Representation

Each permission type has a value:

• Read (r): 4

• Write (w): 2

• Execute (x): 1

Add these values to get permission for each category (Owner, Group, Others). For example:

• rwx (read, write, execute) = 4 + 2 + 1 = 7

• rw- (read, write) = 4 + 2 = 6

• r-- (read-only) = 4

So, rwxr-xr-- translates to 754.

Letter Representation

Think of permissions as three letters for each category:

• Owner: rwx

• Group: r-x

• Others: r--

Mnemonic

Use the mnemonic “Read, Write, Execute” to remember the order, and the numbers 4, 2, and 1 for read, write, and execute.