Set up remote access in UNIX through OpenSSH

Martin Brown (, Freelance Writer, Author

13 Feb 2007

Use OpenSSH to provide a secure environment for running a remote terminal. The basics of OpenSSH and terminal usage are quite simple but, in this article, examine additional elements that allow automatic login to remote hosts, methods for running remote applications, and how to securely copy files between hosts.

About this series

The typical UNIX® administrator has a key range of utilities, tricks, and systems he or she uses regularly to aid in the process of administration. There are key utilities, command-line chains, and scripts that are used to simplify different processes. Some of these tools come with the operating system, but a majority of the tricks come through years of experience and a desire to ease the system administrator’s life. The focus of this series is on getting the most from the available tools across a range of different UNIX environments, including methods of simplifying administration in a heterogeneous environment.

Why use OpenSSH?

The standard networking services that you use every day, such as FTP, Telnet, RCP, remote shell (rsh), and so forth, are fine within a closed environment, but the information that you transfer over the network with any of these services is not encrypted. Anybody with a packet sniffer on your network or on a remote machine can view the information as it is exchanged, sometimes even password information.

Furthermore, with all of these services, the options for auto-login during the process are limited, and often rely on embedding the plain text password into the command line to execute a statement, making the process even more insecure.

The Secure Shell (SSH) protocol was developed to get around these limitations. SSH provides for encryption of the entire communication channel, including the login and password credential exchange, and it can be used with public and private keys to provide automatic authentication for logins. You can also use SSH as an underlying transport protocol. Using SSH in this way means that once you have opened a secure connection, the encrypted channel can exchange all types of information, even HTTP and SMTP, using the same, secure communication mechanism.

OpenSSH is a free implementation of the SSH 1 and SSH 2 protocols. It was originally developed as part of the OpenBSD (Berkeley Software Distribution) operating system and is now released as a generic solution for UNIX or Linux® and similar operating system



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