Terminal services alternatives
Aleksandar Milivojevic
amilivojevic at pbl.ca
Mon Dec 13 15:40:47 UTC 2004
Tom Diehl wrote:
> Hi all,
>
> I was wondering if anyone knows of a linux based solution to Terminal Services
> or Citirx?
You don't need anything extra. X11 is basically networked graphics
protocol. It was designed to be used over the network from the day one.
X11 itself is lightweight, but don't expect to run it comfortably over
the 33.6kbps modem line.
You can login remotely using XDMCP (X Display Manager Protocol). All
you need to do is to configure XDMCP manager (whichever you are using)
to accept connections from network on the server. I haven't done that
since days when xdm (the XDMCP manager distrubted by MIT X11) was the
only implementation available, but it shouldn't be anything complicated.
Today, there are also kdm and gdm (KDE display manager, and Gnome
display manager, and you are probably using one of those two to login on
your console -- haven't done this kind of stuff with them, but they
should basically work the same way xdm does).
Do ps -ef | grep '[gkx]dm' to check out which one you are running.
On classic today's Linux system, XDMCP manager is started from
/etc/inittab during boot, if you are booting into run level 5. It is
the line that calls /etc/X11/prefdm, which than starts XDMCP manager of
your choice (xdm, kdm, or gdm). Configuration files for all three of
them are usually located in /etc/X11. By default, they are configured
not to accept connections from network (they will handle only the console).
On the client side, if clietns are Windows boxes, you'd need to install
some sort of X server (several available, mostly commercial). Almost
all of them support XDMCP. If clients are Linux boxes, just point them
to XDMCP manager you configured in previous step. From that point on,
users will not be able to tell if they are sitting at the console or at
the remote computer. They can even be presented with menu of available
server to connect to (after that point they'll get the very same login
screen as if sitting at the console).
The "just point them" part might be a bit misleading. It is a bit more
work. You need to start X server on the client (not the XDMCP manager)
and instruct it to connect to the server. Do "man Xserver" and look at
XDMCP section. Options that are of interest to you are "-query" to get
login from specific hostname, "-broadcast" to do broadcast on the
network and present list of available XDMCP servers, and "-indirect" to
connect to specific hostname and have XDMCP server on that host present
list of available servers. Also, make sure X server on the client PC is
not started with "-nolisten tcp" (default on Linux). You do want it to
listen on TCP, so that applications from the server can connect to
user's display to open windows.
Note:
If on the server you are booting into run level 3, than XDMCP manager
will not be started. In that case, you need to start it by hand (write
a startup script to be placed in /etc/rc3.d). Configure it *not to*
start X11 server on the console (otherwise, you'll get same thing as if
booting into run level 5, X server running on console).
--
Aleksandar Milivojevic <amilivojevic at pbl.ca> Pollard Banknote Limited
Systems Administrator 1499 Buffalo Place
Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
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