Some user forgot his password and I want to restore it being root. For that I use, in su :
#passwd <user>
passwd: user '<user>' does not exist
I know the user is there because trying via ssh I am asked for the password. Either the user is not in
/etc/passwd/
ssh will ask for a password regardless of whether or not the user exists, in part to help obfuscate where the failure is when a login fails and in part to rate limit the ability to do brute-force type attacks.
If the user is not in /etc/passwd then the user does not exist, at least, the user does not exist as a local user. If you do network logins, the user might still exist wherever those accounts are defined.
