CORRECTION: I only want to see if I do not understand the manual or the system, in admitting regular_user_2 logins, is
malfunctioning. Thanks.

Is regular_user_2 logging in remotely? Maybe something is lost in the translation, but that is the second post where is seems you are logging in locally instead of remotely. Try logging in with the "-vv" verbose option. It will indicate the authentication used. This is displayed at the client. Also look at your logs in the server.

I wonder if the problem has to do with PAM. I would recommend using PubKey authentication in any case and only using PAM for session control.
The instructions should be given in the comments just above the "UsePam Yes" line of /etc/ssh/sshd_config.

Also check the sshd script. Does it use an option which loads in the configuration from a different file?

No. regular_user_2 logs in locally, as every other log into my machine, which doesn't belong to a LAN. More specifically, the whole system consists of a simple home desktop computer. Therefor, any attempt at logging in shall have to be through the console or from the ISP. Also, I'm the only physical user. As to the -v option for login, he does not like it (i don't know if there are several versions of login in linux, but I could contact the author). I thought if I made a syntax error in sshd_config, I could see something in /var/log/messages. But I didn't. I'll rename the configuration file and this will make sshd unable to start. Then I'll know he is reading it.

PAM: I've followed your suggestion about Pubkey and PAM.

The sshd script: No. It doesn't. rc.sshd invokes sshd with
no options, in particular no -f option. So, sshd should read /etc/ssh/sshd_config, the default path for the configuration file for sshd.

Most respectfully, E.S.

ssh is only for remote logins. The local logins do not use it, by default.
In fact, even for remote logins you have to specify ssh ie

ssh user@system

Of course you can do that from the local console, but that would be very unusual.

To disable a user's acct, either temporarily or permanently, see http://www.networkdictionary.com/software/Linux325.php

Incidentally, there are a lot of bot scripts trying to brute force root logins via ssh, so best to set

PermitRootLogin no

in /etc/ssh/sshd_config and restart sshd:

service sshd restart

Most kind of you, chrism01. It's very clearly stated in ssh man page and I've made a fool of myself. Sorry for the delay.

E.S.