From LQWiki

SSH is short for Secure Shell. It allows you to execute commands on a remote computer and much more. It uses encryption for the data transfer.

The ssh man page gives you an overview of the capabilities of ssh, as does using SSH on this site.

• SSH is more secure than telnet thus it is recommended for use with Linux systems.
• In Red Hat & fedora these RPM packages must be installed: openssh-clients, openssh

Contents 1 Using SSH 1.1 TroubleShooting 1.2 See also 2 SSH Client Software 3 Troubleshooting SSH Connections 4 See also

Using SSH

Main article: Using ssh

1. Type:

# ssh youruser@192.168.0.2

In this case, 192.168.0.2 is your target's IP address, where you have a user youruser. You can also use a hostname, in our examples target instead of an IP address. 1st time you log in to a system a mesage will come up:

 The authenticity of host 'xxxxx' can't be established.
 DSA key fingerprint is 94:68:3a:3a:bc:f3:9a:9b:01:5d:b3:07:38:e2:11:0c.
 Are you sure you want to continue connecting (yes/no)?  <-- type in y for yes or n for no

If you type yes then:

 Warning: Permanently added 'xxxxxxxx' (RSA) to the list of known hosts.

2. Now type in the password

3. If you don't want to log in but you want to execute a command, do this:

# ssh youruser@target date

This will execute the command date as user youruser on the computer target.

TroubleShooting

If ssh does not work, you may have switched on the firewall. Make sure your target computer has port 22 open towards your computer:

telnet target 22
Trying 192.168.0.2...
Connected to target.
Escape character is '^]'.
SSH-2.0-OpenSSH_4.6

See also

• passWordLess LogIns

SSH Client Software

• OpenSSH
• lsh
• PuTTY

Some implementations for other OS:

• SSHDOS - client for MS-DOS.
• PuTTY - client for console access and X-Windows forwarding on Windows.
• WinSCP [1] - open source SFTP and SCP client.
• The Cygwin UNIX environment for Windows includes OpenSSH's client and server.

Troubleshooting SSH Connections

SSH clients and servers can generate a lot of debug information.

On the server, kill sshd, and then start the server in debug mode.

$ killall sshd PID
$ /usr/sbin/sshd -ddde

Leave the window open, so you can see the output it generates.

Then on the client, run:

$ ssh -vvv (target-host)

See also

• Using SSH -- copying files, remoting, clients
• SFTP - secure file transfer protocol
• Scp - secure copy protocol
• Sshd - SSH daemon
• SFTPPlus [2], Extends SFTP with additional audit & automation
• Tunneling with SSH Using SSH to tunnel TCP connections.