This question already has an answer here:

My (admittedly dated) understanding of unix is that in /etc/passwd if the second field is 'x' then the identity can login with a passwd that matches a hash found in /etc/shadow.

However, when I list /etc/passwd I see that all the identities are marked with an 'x' including those that should not be able to login. In the /etc/shadow file, the no-login entities have a double bang "!!" in the hash field whereas the loginable users have the expected hash.

So, I presume this double bang convention is some alternative to the old (?) mechanism of using '*' to mark no-login users. Why is the old method no longer used?

marked as duplicate by Rui F Ribeiro, Thomas, Jeff Schaller, Mr Shunz, elbarna Jan 28 at 10:48

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Browse other questions tagged or ask your own question.