OpenSSH

The OpenSSH suite provides secure remote access and file transfer. Since its initial release, it has grown to become the most widely used implementation of the SSH protocol. During the first ten years of its existence, it had largely replaced older corresponding unencrypted tools and protocols. The OpenSSH client is included by default in most operating system distributions, including MacOS, AIX, Linux, BSD, and Solaris. Any day you use the Internet, you are using and relying on hundreds if not thousands of machines operated and maintained using OpenSSH. A survey in 2008 showed that of the SSH servers found running, just over 80% were OpenSSH. Even with the advent of the Internet of Things and the increased use of IPv6, a cursory search of Shodan for SSH-2.0 services on port 22 in November 2022 showed 87% of responding addresses running OpenSSH.

OpenSSH was first released towards the end of 1999. It is the latest step in a very long and useful history of networked computing, remote access, and telecommuting.

This book is for fellow users of OpenSSH to help save effort and time through using OpenSSH, and especially SFTP, where it makes sense to use it.

Introduction

 * /Overview/
 * /Why Use Encryption/
 * /SSH Protocols/
 * /Other SSH Implementations/

Client-Server

 * /Client Applications/
 * /Client Configuration Files/
 * OpenSSH Server
 * /Pattern Matching in OpenSSH Configuration/

Utilities

 * /Utilities/
 * Third Party Utilities

Logging, Troubleshooting, and Development

 * Logging and Troubleshooting
 * /Development/

Cookbook

 * Remote Processes
 * Tunnels
 * Automated Backup
 * File Transfer with SFTP
 * Public Key Authentication
 * Certificate-based Authentication
 * Host-based Authentication
 * Load Balancing
 * Multiplexing
 * Proxies and Jump Hosts