===== DropBear ===== 
OpenSSH can be replaced by dropbear to save memory. Stop OpenSSH and prevent it from running at start: 
<code bash>
touch /etc/ssh/sshd_not_to_be_run service ssh stop
</code> 
Install Dropbear 
<code bash>
apt-get install dropbear
</code>
Set NO_START=0 in /etc/default/dropbear so dropbear can run as a daemon:
<code bash>
vi /etc/default/dropbear
</code>
Start Dropbear:
<code bash>
/etc/init.d/dropbear start
</code>