Last Updated: 2024-04-26

What does 755 mean? Would it be OK to chmod -R 755 .?

Each of the three digits represents the permissions to a certain entity :

• user (7)
• group (5)
• others (5)

As for the actual numbers, they are the sums of the permission bits. The components are:

• read: 4
• write: 2
• execute: 1

These are then summed. Thus:

• To represent rwx triplet use 4+2+1=7
• To represent rw- triplet use 4+2+0=6
• To represent r– triplet use 4+0+0=4
• To represent r-x triplet use 4+0+1=5

Returning to chmod -R 755. This sets read and execute bit on every file in this tree for every user. This is probably a bad call (the execute part)

Instead you just want the execute permission on a directory to allow other users to list the contents of those directories and to cd into them. $ find storage/ -type d -exec chmod 755 {} \;

(Remember: you need execute permissions on a directory to go into it)

How to remember

They are powers of 2:

• r=4 (read)
• w=2 (write)
• x=1 (execute)

Trick: Least permission, biggest number.

Sum them together to get desired number: e.g. if you want rwx, then that's 4 + 2 + 1 = 7. If you want your group and others to have read only, then they both get 4. Now concatenate to get 744.

To change many files, globbing does not work. Use chmod -R 744 folder

Resources

• https://www.cyberciti.biz/faq/unix-linux-bsd-chmod-numeric-permissions-notation-command/