How to install 2 X Server

[Nifty Hat Mitch]

On Sat, Jul 31, 2004 at 06:51:10AM +0300, regatta wrote:
> Reply-To: For users of Fedora Core releases <fedora-list at redhat.com>
> 
> Thak you all for the replys
> I don't want to run 2 X servers, I want to install 2 versions because
> some of my users want to use some libraries in the new version without
> losing the old one
...
> > > > smarty pants!
> > > Sorry, I don't get the joke. Is it one?

Jokes in a multi language community can be fun.
 ;-)


Yes you can have a second environment for X.  Developers do this all the
time.  For X this is not trivial and involves a number of layers that you
have not been clear about.  There will always be some hooks left in
the source tree that make it possible.

to start...
   /usr/lib/X11 is linked to ../X11R6/lib/X11

There is no reason you cannot build and populate ../X11R6modA.  Then
fiddle with the ld link load paths and $PATH so your users can use
what ever they want.

Since we are talking about nearly 4000 files (fonts, shared objects,
programs, multi language support and more) this task is bigger than
a bread box.

Since many library functions are controlled by 'ld', it is possible to
set one or more environment variable to control dynamic linking or 
even set things at the link stage when the object is compiled.
See the ld man page... 

i.e. LD_RUN_PATH LD_LIBRARY_PATH 

This trick of taking control of the link loader (ld) is commonly used
to develop and test new library code (Fortran libs, Perl libs, c
language, math libs, any .so ).  You will see examples in the context
of Java.

In my /usr/bin/java I see lines like:

  elif [ "`echo $1 |cut -b1-2`" = "-D" ]; then
    if [ "`echo $1 |cut -b1-20`" = "-Djava.library.path=" ]; then
       export LD_LIBRARY_PATH=`echo $1 |cut -b21-`:$LD_LIBRARY_PATH
 
This is an education:

 $ find /usr/X11R6/ -type f -print0 | xargs -0 grep PATH


The point is that depending on what your users are  asking of you,
it can be easy or just a pain.

Little  of this demands root permissions with the possible exception of
the server itself.   "startx" could be hacked to have a clone called
"newstartx".  It can reset search paths and fun stuff as needed.

Are these remote users?


-- 
	T o m  M i t c h e l l 
	Just say no to 74LS73 in 2004