OpenSSH

OpenSSH is a compatible, free open source implementation of the original SSH protocol. It enables you to replace obsolete, insecure protocols and services (like Telnet, rlogin/rsh/rcp), or – if a replacement is not possible – to provide additional security for them (via tunneling).

You can open terminal sessions, X sessions or copy data. Therefore SSH is often used for remote maintenance.

Main features:¹⁾

• Strong Encryption
• X11 Forwarding (encrypt X Window System traffic)
• Port Forwarding (encrypted channels for legacy protocols)
• Strong Authentication (Public Key, One-Time Password and Kerberos Authentication)
• Agent Forwarding (Single-Sign-On)
• SFTP client and server support in both SSH1 and SSH2 protocols.
• Kerberos and AFS Ticket Passing
• Data Compression

The main tools provided by OpenSSH are:

• sshd – The OpenSSH server daemon/service
• ssh – The OpenSSH client
• scp – secure copy, similar to cp
• sftp – secure file transer programm, similar to ftp

Other important parts:

• ssh-add
• ssh-agent
• ssh-askpass
• ssh-copy-id²⁾
• ssh-keygen – Generates SSH keys
• ssh-keyscan
• ssh-argv0

For the sake of clarity, information about the different OpenSSH tools and types of use are distributed over single pages:

• ssh (OpenSSH client program) – ssh is the SSH client program OpenSSH provides. It is used for logging in to a remote machine and for executing commands on it.
• sshd (OpenSSH server daemon) – sshd is the SSH server daemon OpenSSH provides. It is used for providing clients access via SSH to a machine, e.g. for executing commands on it.
• file-transfer – Securely copy files using SSH.
• SSH keys – It is possible to use Public-key cryptography instead of passwords for authentication.

• Seahorse – Comfortable GUI to manage your GnuPG and SSH keys.
• putty – Cross platform terminal emulator (SSH/Telnet/rlogin/raw TCP) including session management GUI.
• FileZilla – Free and fast (S)FTP client with GUI.

• OpenSSH project website
• OpenSSH
• SSH
• LinuxWiki.org: OpenSSH