Linux.Desktop.Hacks [Electronic resources] نسخه متنی

Hack 31. Run Your Desktop over the Internet

You can access your desktop system and run
graphics applications from remote systems at close to full speed,
even over dial-up connections.

You might want to access a
desktop computer remotely for numerous
reasons. Perhaps you are travelling and you forgot an important file
on your home machine. You need to edit it, but the application you
need isn't on your laptop. It would be nice to
connect to your home machine over the Internet, edit the file using
software on the desktop, and then transfer the file to your laptop. A
number of technologies are available for running applications from
remote locations, or remotely sharing desktops; the X Window System
has built-in network transparency that allows you to run applications
on one machine and display them on another [Hack #32], and the different versions
of the VNC protocol allow you to use the desktop on another machine
[Hack #30] ). Though each method
has its purpose and excels at what it does, both also have one
drawbackthey require significant bandwidth. Remote X
applications or VNC desktops are pretty slow, even over a DSL or
cable modem connection.

NX, from NoMachine (http://www.nomachine.com), is an add-on to X
that accelerates remote X applications and can be used to run a full
remote desktop at near-native speeds, even over a 56K modem
connection. NX works much like a proxy cache for the X protocol,
caching and compressing requests and responses to and from the X
client and server. This dramatically reduces the network traffic of
the X protocol and works in a way that is transparent to the X
client. All the NX libraries and components are open source, as is
the NX client software. However, the servers NoMachine provides are
proprietary, although a free trial period of the personal edition is
available, which allows single-client access. In addition, the FreeNX
project uses the open source NX libraries to create an open source NX
server. The following examples use the personal server and client
software from NoMachine.

4.11.1. Installing the NX Server and Client

On the machine on which you want to run the remote
session, you need to install an NX server and client. Packages for
various flavors of Linux are available from http://www.nomachine.com. Download the NX
Server Personal Edition for your distribution, along with a client,
and install both in the normal way. For example:

foo@bar:~# rpm -i nxserver-1.4.0-99.i386.rpm
foo@bar:~# rpm -i nxclient-1.4.0-75.i386.rpm

On the machine on which you want to display the remote session, you
need to install the NX client. Clients for Linux, Mac OS X, and
Windows are available from the same web site as the server.

4.11.2. Setting Up the NX Server

Once NX is installed, you can start the NX
server using this command (run as root):

foo@bar:~# /usr/NX/bin/nxserver -start

Now you need to add user sessions to the server using this command:

foo@bar:~# /usr/NX/bin/nxserver --useradd username

where username is the name of a preexisting user
on the server system. Next you are prompted to set a password for
this session. Once that's done, you can connect your
client machine to the server using the NX client. Go to a separate
machine and run the client using this command:

foo@bar:~# /usr/NX/bin/nxclient

For the first connection this starts a wizard to collect the
connection details. On the second wizard page you can give the
session a descriptive name, enter the NX server IP address, and
select the type of connection between the client and server.

On the third wizard page, you can choose your protocol type (the NX
client is also an RDP and VNC client), the type of desktop session to
run the NX server, and the size of the window to display the remote
desktop. If there are firewalls [Hack #81] and you only have Secure
SHell (SSH) access, check the "Enable SSL encryption
of all traffic" box, as this tunnels all
communication through SSH (i.e., you only need port 22 open) and has
the added bonus of encrypting all the NX traffic. If you
don't want to tunnel the traffic over SSH,
you'll need to open ports 1000, 5000, and 7000 for
the first session, 1001, 5001, and 7001 for the second session, and
so oni.e., three ports for each session started.

Finally, on the fourth wizard page, you can choose to create a
desktop shortcut for this session and edit the advanced
configuration. Once the wizard is finished, you should have a
connection dialog with the Login and Session details filled in.

Now type in the password you set on the NX server and click Login.
Once this connects and authenticates you should have a complete
remote desktop in a window on your client machine.

4.11.3. Further NX Server Commands

Now that you know how to
create a basic connection, a few other useful commands for the NX
server might interest you. These commands need to be run as root. To
see a list of all NX users, type this command:

foo@bar:~# /usr/NX/bin/nxserver --userlist

To delete an NX user (this deletes the user from NX, not as a user of
the system), issue the following:

foo@bar:~# /usr/NX/bin/nxserver --userdel  username

where username is the name of the NX
account you want to delete.

Paul Cooper