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<div id="logo"><a href="IDH_XDMCP.htm"><img src="X2.bmp" title="XLaunch XDMCP settings" alt="XLaunch XDMCP settings"></a><span style="color:#2b5e82;vertical-align:super;font-family:Bitstream Vera Sans,sans-serif;font-weight:bold;font-size:30pt;">Launch</span></div>
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<h2><a name="1"></a>Start program</h2>
Enter the name and parameters of an X client you want to start and display on the X server.
For example, to run <b>xeyes</b>
<pre>xeyes -fg red
</pre>
<h3><a name="3"></a>Start program on this computer</h3>
Start the chosen or entered program (with parameters as required) on the local machine.
<h3><a name="4"></a>Start program on remote computer</h3>
As above but the program will be run on a remote machine.
<h4><a name="6"></a>Using SSH</h4>
An X client program can be started remotely via SSH.<p>
There is no mechanism to save a ssh password for security reasons.<p>
SSH X11 forwarding must be enabled in the <b>sshd</b> daemon's sshd_config file on the remote machine, e.g.
<pre>
X11Forwarding yes
</pre>
<h5><a name="7"></a>Prompt for ssh password/passphrase</h5>
<b>ssh</b> is run within a terminal, allowing the password or passphrase to be entered interactively.<p>
<h5><a name="8"></a>Use keychain to contact ssh-agent</h5>
From <b>bash</b> you can start a <b>ssh-agent</b> daemon using <b>keychain</b>
(which saves the <b>ssh-agent</b> environment variables to ~/.keychain/${HOSTNAME}-sh,
so that subsequent non-interactive shells, such as used by xlaunch can source
the file and make passwordless ssh connections).<p>
e.g. to start <b>ssh-agent</b> and load the key ~/.ssh/ida_rsa into it:
<pre>
$ keychain id_rsa
</pre>
You will be prompted for the key's passphrase.
<p>
Subsequently, xlaunch can run <b>ssh</b> using this key to authenticate without
prompting for the passphrase.<p>
When finished, use <b>keychain</b> to stop <b>ssh-agent</b>
<pre>
$ keychain -k all
</pre>
<p>
See <b>man keychain</b> for more details.
<h5><a name="9"></a>Password-less public key authentication</h5>
If neither of the options above are selected, you must arrange for
<b>ssh</b> to be able to non-interactively authenticate with the remote
<b>sshd</b> i.e. install on the remote machine a public key corresponding
to a local private key which has no passphrase.
<p>
e.g.
Create a passphrase-less key-pair, using
<pre>
ssh-keygen -f ~/.ssh/example-key -N ''
</pre>
append the public key to your ~/.ssh/authorized_keys file on the remote machine,
<pre>
ssh-copy-id -i ~/.ssh/example-key.pub <i>user@server</i>
</pre>
and instruct the local ssh to use the corresponding private key, by adding to ~/.ssh/config
(possibly under an appropriate Host section)
<pre>
IdentityFile ~/.ssh/example-key
</pre>
<p>
See the "AUTHORIZED KEYS FILE FORMAT" section of <b>man sshd</b> and
the "IdentityFile" section of <b>man ssh_config</b> for more details.
<p>
<h5><a name="10"></a>Troubleshooting SSH</h5>
The command run automatically after the X server has started is
<pre>ssh -Y <user@computer> <program>
</pre>
Try this by hand, from a shell, if you have problems.<p>
<h4><a name="11"></a>Using rsh</h4>
An X client program can be started remotely via rsh.<p>
You must configure rsh for password-less authentication.<p>
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