How to Disable Password Authentication for SSH

Once you have SSH Keys configured, you can add some extra security to your server by disabling password authentication for SSH. (Note that if you do lose your private key, this will make the server inaccessible and you will need to contact HostGator to have this re-enabled.)

To disable this setting, you can do the following:

vi /etc/ssh/sshd_config

In this file, set the following settings to the following values. If these settings are already in the file, set them to “no” rather than add new lines.

ChallengeResponseAuthentication no
PasswordAuthentication no
UsePAM no

Once this is done, restart the SSH daemon to apply the settings.

/etc/init.d/sshd restart

Source: http://support.hostgator.com/articles/specialized-help/technical/how-to-disable-password-authentication-for-ssh

How Do I Display the Contents of a Linux File?

$ cat filename

The cat command (short for concatenate) shown in this example is like the DOS type command. In response to the command cat pig_info, the system simply splatters the file on the screen. If there is more data in the file than will fit on one screen, the contents whiz by before you can see it. The more command solves this problem by displaying the file screen by screen:

$ more filename

Source: http://lowfatlinux.com/linux-display-files-cat.html

Grep UID in Plesk from Qmail log

Click on the header link in the mail server queue:

Received: (qmail 30501 invoked by uid 10077); 3 Dec 2009 21:47:42 -0500
Date: 3 Dec 2009 21:47:42 -0500
Message-ID: <20091204024742.30498.qmail@hostserver.com>
To: email@domain.com
Subject: This is a test.
MIME-Version: 1.0
Content-type: text/html; charset=iso-8859-1
From: <user@domain.com>

It says its invoked by uid 10077 which corresponds to the account on the /etc/password file:

-bash-3.2# more /etc/passwd | grep 10077
username:x:10077:2522::/var/www/vhosts/domain.com:/bin/false