In Ubuntu 10.04LTS Lucid Lynx and newer, there are two primary Jabber servers to use ejabberd and jabberd2.

Ejabberd

Ejabberd is a high-performance Jabber/XMPP server, written in erlang. It comes with a built-in web-based management interface.

Installation

To install the server and its components, run:

sudo apt-get install ejabberd

After it is installed, you need to edit the configuration file found at /etc/ejabberd/ejabberd.cfg.

In the configuration file, you need to add the host name you want the server to use (unless you only want to run on localhost). Change:

{hosts, ["localhost"]}.

to

{hosts, ["localhost","servername.com"]}.

In addition, you need to create an admin user. Change:

{acl, admin, {user, "", "localhost"}}.

to

{acl, admin, {user, "admin-name", "servername.com"}}.

Now, restart the service:

sudo service ejabberd restart

Finally, set the password for your admin user:

sudo ejabberdctl register admin-name servername.com password

All set. For any further configuration, you can log in to the web-based management panel. In your web browser, go to http://servername.com:5280/admin and enter the admin username and password. You can get more details on use the web admin page from the ejabberd site