Chapter 18. OpenSSH

Chapter 18. OpenSSH

18.1. Features of SSH
18.1.1. Why Use SSH?
18.2. SSH Protocol Versions
18.3. Event Sequence of an SSH Connection
18.3.1. Transport Layer
18.3.2. Authentication
18.3.3. Channels
18.4. Configuring an OpenSSH Server
18.4.1. Requiring SSH for Remote Connections
18.5. OpenSSH Configuration Files
18.6. Configuring an OpenSSH Client
18.6.1. Using the ssh Command
18.6.2. Using the scp Command
18.6.3. Using the sftp Command
18.7. More Than a Secure Shell
18.7.1. X11 Forwarding
18.7.2. Port Forwarding
18.7.3. Generating Key Pairs
18.8. Additional Resources
18.8.1. Installed Documentation
18.8.2. Useful Websites

SSH™ (or Secure SHell) is a protocol which facilitates secure communications between two systems using a client/server architecture and allows users to log into server host systems remotely. Unlike other remote communication protocols, such as FTP or Telnet, SSH encrypts the login session, rendering the connection difficult for intruders to collect unencrypted passwords.

SSH is designed to replace older, less secure terminal applications used to log into remote hosts, such as telnet or rsh. A related program called scp replaces older programs designed to copy files between hosts, such as rcp. Because these older applications do not encrypt passwords transmitted between the client and the server, avoid them whenever possible. Using secure methods to log into remote systems decreases the risks for both the client system and the remote host.


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