Red Hat Enterprise Linux 3: System Administration Guide
Prev |  | Next

# Chapter 22. OpenSSH

OpenSSH is a free, open source implementation of the SSH (Secure S Hell) protocols. It replaces `telnet`, `ftp`, `rlogin`, `rsh`, and `rcp` with secure, encrypted network connectivity tools. OpenSSH supports versions 1.3, 1.5, and 2 of the SSH protocol. Since OpenSSH version 2.9, the default protocol is version 2, which uses RSA keys as the default.

# 22.1. Why Use OpenSSH?

If you use OpenSSH tools, you are enhancing the security of your machine. All communications using OpenSSH tools, including passwords, are encrypted. `Telnet` and `ftp` use plain text passwords and send all information unencrypted. The information can be intercepted, the passwords can be retrieved, and then your system can be compromised by an unauthorized person logging in to your system using one of the intercepted passwords. The OpenSSH set of utilities should be used whenever possible to avoid these security problems.

Another reason to use OpenSSH is that it automatically forwards the `DISPLAY` variable to the client machine. In other words, if you are running the X Window System on your local machine, and you log in to a remote machine using the `ssh` command, when you run a program on the remote machine that requires X, it will be displayed on your local machine. This feature is convenient if you prefer graphical system administration tools but do not always have physical access to your server.

Prev | Home | Next
Additional Resources | Up | Configuring an OpenSSH Server