2012-04-22.

NoMachine:  NXclient and NXserver.

http://en.wikipedia.org/wiki/NX_technology
"NX technology is a computer program that handles remote X Window System connections, and attempts to greatly improve on the performance of the native X display protocol to the point that it can be usable over a slow link such as a dial-up modem. It wraps remote connections in SSH sessions for encryption.
It is developed by Gian Filippo Pinzari at the Italian software company NoMachine. The NX scheme was derived from that of DXPC – the Differential X Protocol Compressor project.[1]
NX software is currently available for Windows, Mac OS X, Linux, and Solaris. NoMachine has clients available for Windows and Mac OS X, and Google makes a freely available Open Source GPL2 version of the server called NeatX"

This is a very interesting program.  We've used some form of it since about 
2004, as a means of accessing servers with good graphics support and speed.
One advantage over VNC has been support for acceleration, but with TigerVNC
this isn't such a problem.  
Another big advantage (for deployment) is that NX uses existing SSH for 
transport, integrates this in the client, gives an option of which desktop 
environment to use, and reattaches to an existing session.
This, available even for the m$-windos client, simplifies greatly the use 
of remote connections by our "lusers", who otherwise end up with great 
difficulties trying to tunnel connections securely with putty or vpn, or 
leaving dozens of old vnc sessions running, always creating new ones.


The core libraries have until 2011 been Free Software (GPL).
Since then (v4), even these have been closed.
Up to v3, the libraries were used for free clients and servers, as well 
as the non-free clients and servers provided by Nomachine itself.
Nomachine's nxclient was (and is) clearly the most convenient to use; 
an existing Free alternative is qtnx.
Nomachine sells an nx server with larger numbers of available slots, and
gives away a (still proprietary) server limited to 2 slots.  The freenx 
server hasn't the limitation.

We've previously used the proprietary packages for client and server, 
in Gentoo -- the free (unlimited slots) server caused hassle last time 
I tried it sometime around 2008.

Now, for the new computation servers with Scientific Linux, it was worth 
trying to get the unlimited server version working and to advocate its 
use as the normal way of connecting.  
But the RHEL/SL distribution doesn't include NX.
The following was a handy quick-guide to getting it.
One could otherwise presumably enable all the ATrpms repositories in 
/etc/yum.repos.d/ , to get binaries, but I don't like having ATrpms
in the normal list of repositories (yum install and yum update problems
sometimes).

---
http://blog.yibi.org/2011/08/10/installing-freenx-on-red-hat-enterprise-linux
2012-04-22.
Prescription for freenx server on RHEL6 (thus SL6, CentOS6).

Get the sources:
    wget http://dl.atrpms.net/all/nx-3.3.0-38.src.rpm
    wget http://dl.atrpms.net/all/freenx-server-0.7.3-18.src.rpm
Build binary rpms (needs some extra tools from the base SL6 distribution).
    rpmbuild --rebuild nx-3.3.0-38.src.rpm
    rpmbuild --rebuild freenx-server-0.7.3-18.src.rpm
   then install the two rpms thus produced.

Configure:
  /usr/libexec/nx/nxsetup
(say NO to custom keypair: that would prevent the "normal" nx clients downloaded
by users from connecting easily on the first time).

Tell users to use the normal NX client.
---