Why All Users Can Write to /tmp

I've been wondering for a while now: how come all the users on a system are able to write to the /tmp directory. And turns out, that /tmp is a special directory which uses sticky bit to achieve just that.

What is /tmp?

/tmp is a special directory used for storing temporary files created by users and system processes.

Permissions Explained

By default, /tmp is owned by root but has the following permissions:

drwxrwxrwt

This breaks down as:

• drwxrwxrwx: All users can read, write, and execute (list contents) in /tmp.

• The t (sticky bit): Ensures only the owner of a file (or root) can delete or rename it.

Why is /tmp World-Writable?

• Temporary Storage: Allows any user or process to create files for temporary use.

• Security: The sticky bit prevents users from deleting or renaming files that don’t belong to them.

Summary

All users can write to /tmp because of its world-writable permissions and the sticky bit, which together provide a secure and flexible temporary workspace for everyone on the system.

Reference(s):

• Reddit - Linux4Noobs

• Stack Exchange