How to Install FreeNX on Ubuntu

1. Update your /etc/apt/sources.list with the following settings. (This is from
the Ubuntu Guide)

-----------------cut-------------------
## Add comments (##) in front of any line to remove it from being checked.
## Use the following sources.list at your own risk.
## You may replace "us" with your country code to get the closest mirror.

deb http://us.archive.ubuntu.com/ubuntu breezy main restricted
deb-src http://us.archive.ubuntu.com/ubuntu breezy main restricted

## MAJOR BUG FIX UPDATES produced after the final release
deb http://us.archive.ubuntu.com/ubuntu breezy-updates main restricted
deb-src http://us.archive.ubuntu.com/ubuntu breezy-updates main restricted

## UBUNTU SECURITY UPDATES
deb http://security.ubuntu.com/ubuntu breezy-security main restricted
deb-src http://security.ubuntu.com/ubuntu breezy-security main restricted

deb http://security.ubuntu.com/ubuntu breezy-security universe
deb-src http://security.ubuntu.com/ubuntu breezy-security universe

## UNIVERSE AND MULTIVERSE REPOSITORY (Unsupported by Ubuntu. Use at own risk.)
deb http://archive.ubuntu.com/ubuntu breezy universe multiverse
deb-src http://archive.ubuntu.com/ubuntu breezy universe multiverse

## BACKPORTS REPOSITORY (Unsupported. May contain illegal packages. Use at own risk.)
deb http://archive.ubuntu.com/ubuntu breezy-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu breezy-backports main restricted universe multiverse

## PLF REPOSITORY (Unsupported. May contain illegal packages. Use at own risk.)
deb http://packages.freecontrib.org/ubuntu/plf breezy free non-free
deb-src http://packages.freecontrib.org/ubuntu/plf breezy free non-free

## For FreeNX only
deb http://seveas.ubuntulinux.nl/ breezy-seveas freenx

-----------------cut-------------------

2. apt-get update
3. apt-get install binutils
4. apt-get install ssh
5. apt-get install freenx, (choose custom keys after installation)

6. add the user you want to give access. This will copy the generated public key to the right place (.ssh/authorized_keys2) of their home directories.

This command adds the user "ubuntu"

root@vmware:/home/admin# nxserver --adduser ubuntu
NX> 100 NXSERVER - Version 1.4.0-44 OS (GPL)
NX> 1000 NXNODE - Version 1.4.0-44 OS (GPL)
NX> 716 Public key added to: /home/admin/.ssh/authorized_keys2
NX> 1001 Bye.
NX> 999 Bye

7. Now update the nxserver with the user's password
root@vmware:/home/admin# nxserver --passwd ubuntu
NX> 100 NXSERVER - Version 1.4.0-44 OS (GPL)
New password:
Password changed.
NX> 999 Bye

Once that’s been done, install an NX client, there are plenty available from the NoMachine web site.

At this point you should be able to configure your connection and you’re almost ready to go. If you try to log in it won’t let you as you need to copy the key. The custom key lives in /var/lib/nxserver/home/.ssh/client.id_dsa.key. Copy this over to your client host and import it. You should now be ready to log into a fully functional NX environment.

Reference:
http://www.snakeoillabs.com/2005/10/27/freenx-on-ubuntu-breezy-howto