Learning Red Hat Linux, Second Edition

The Secure Shell

The Secure Shell (SSH) lets you connect to a system from another system via TCP/IP and obtain a shell prompt, from which you can issue commands and view output in a secure fashion. If you are not familiar with SSH but are familiar with Telnet, SSH works similarly. SSH differs from Telnet in that conversations between SSH and its clients are sent in encrypted form so hackers cannot easily discover private information, including user account names and passwords.

Installing SSH

The SSH client lets you remotely log in to systems that provide an SSH server. It’s likely that the installation procedure installed the SSH client for your use. To check whether it’s installed, issue the command:

               rpm -q openssh

If openssh is installed, the command reports its version number; otherwise, the command reports that openssh is not installed.

You can manually install the SSH client by using GnoRPM to install the following packages:

• openssh

• openssh-clients

• openssh-askpass

• openssh-askpass-gnome

To install the SSH server, use GnoRPM to install the openssh-server package.

Once installed, the SSH server should start automatically. To check the status of the SSH server, issue the command:

               service sshd status

The command’s output should report that the server is running. If not, you can manually start the server by issuing this command:

               service sshd start

If you want to stop the SSH server, issue this command:

               service sshd stop

Tip

The SSH service has several configuration files, ...