[TUHS] Questions about * and ! in the password field of passwd and shadow

[Marc Haber via TUHS]

Hello Everybody,

On Wed, Jan 07, 2026 at 08:34:39PM +0100, Marc Haber wrote:
>I am wondering about the difference between ! and * in the password 
>field of /etc/shadow and before its invention in /etc/passwd. I think 
>that until some ten years ago, there was still a difference between 
>both, with one of the versions preventing login via password (but 
>keeping it possible to use, for example, an ssh key to log in) and the 
>other also making it impossible to use an ssh key to log in. I think 
>that one also prevented su'ing to that account.

Thank you for this fruitful discussion that has taught me that this has 
never been formally specified, and that the different flavours of 
Unixoid operating systems are doing their own thing in their 
/etc/passwd. Short research also told me that the format of /etc/passwd 
or other backing stores for the user account database are nowadays 
neither part of POSIX nor of SuS.

I have learned something. Your answers are appreciated.

Greetings
Marc

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