SSH server !!!!!

Q:How to restrict users log onto a system via SSH server?

A. OpenSSH server allows to specify usernames for login. According to man page syntax is as follows::

AllowUsers user1 user2

AllowUsers keyword can be followed by a list of user name patterns, separated by spaces. If specified, login is allowed only for user names that match one of the patterns. * and ? can be used as wildcards in the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts.

Step # 1: Open sshd_config file

# vi /etc/ssh/sshd_config

Step # 2: Add a user

Only allow user vinod to login by adding following line:

AllowUsers vinod

Step # 3: Restart sshd

Save and close the file.

In the above example, user vinod has already been created on the system. Now just restart sshd:

# service sshd restart