</source>
You might get 'database' errors, in which case you should install <code>dselect</code> and update that as well (all as root, or with sudo):
<source lang="bash">
apt-get update
apt-get install dselect
dselect update
apt-get -u dselect-upgrade
</source>
There are other tools to do the job too, and the tools you want to use for this depend on how automated you aim for this task to be, and how much you need/want to be able to customize each machine as it's being installed.