h1. Create SSH keys for Login

As an example we create keys for *titan* cluster.

h2. Login to the computer from which you want to access the Cluster and change into directory *~/.ssh/*

<pre>
cd ~/.ssh/
</pre>

If you don't have such directory, create it and change into it.

Create key pair using the following command.

*DO NOT SETUP PASSPHRASE !!*

<pre>
ssh-keygen -f id_rsa_titan -t rsa
</pre>

Now you have key pair:

* *id_rsa_titan* is your private key. *Keep it secret*.
* *id_rsa_titan.pub* is your public key.

Make sure the private key has the right protection:

<pre>
chmod 400 id_rsa_titan
</pre>

Send the public key (id_rsa_titan.pub) to the Cluster:

*DO NOT SEND FILE id_rsa_titan WHICH IS YOUR PRIVATE KEY AND SHOULD BE KEPT SECRET.*

<pre>
scp id_rsa_titan.pub titan.utu.fi:
</pre>

Login into titan.utu.fi and while logged change into directory *~/.ssh*

<pre>
ssh titan.utu.fi
cd ~/.ssh/
</pre>

Depending on whether you already have file named *authorized_keys* continue with either *Option A* or *Option B*.

*Option A*) If you have file named *authorized_keys* add contents of id_rsa_titan.pub at the end of *authorized_keys*

<pre>
cat ../id_rsa_titan.pub >> ./authorized_keys
</pre>

Now you can get rid of file ../id_rsa_titan.pub

<pre>
rm ../id_rsa_titan.pub
</pre>

*Option B*) If you don't have file named *authorized_keys* rename id_rsa_titan.pub to *authorized_keys* and move it:

<pre>
mv ../id_rsa_titan.pub ./authorized_keys
</pre>

Logout from titan.utu.fi

Edit your local config file ...

<pre>
emacs config
</pre>

... and add the following lines:

<pre>
Host titan
User YOUR_USERID
HostName titan.utu.fi
IdentityFile ~/.ssh/id_rsa_titan
</pre>

Replace YOUR_USERID with your user id in titan.

You setup is done now and you should be able to login:

<pre>
ssh titan
</pre>