R help - Jul 2003 - General X11 Problems

Hi

You may remember a while ago I was having problems with creating jpegs using R
over CGI.  I solved this on my LAPTOP (*grins*) by

- executing "xhost +localhost" from the command line 
- putting "SetEnv DISPLAY=:0.0" in my httpd.conf (apache)

And all worked well.  Now I'm trying to move the whole system onto my shiny
new server - and encountering yet more problems with X11() (why, god why???).

Quick rundown - SUSE Linux 8.1, R version 1.7.1, Apache 1.3.27.
>From the COMMAND LINE, as the user my webserver runs as, I get:
>jpeg(file="blah",height=480,width=480)
1633: X11 connection rejected because of wrong authentication.
X connection to localhost:12.0 broken (explicit kill or server shutdown)
>From the COMMAND LINE as root, it works fine :-D
Over CGI, running as webmstr and with SetEnv DISPLAY=:0.0, I get:

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

Error in X11(paste("jpeg::", quality, ":", filename, sep =
""), width,  :
	unable to start device JPEG
In addition: Warning message: 
unable to open connection to X11 display`' 
Execution halted

Over CGI, running as webmstr and with SetEnv DISPLAY=:12.0, I get:

Error in X11(paste("jpeg::", quality, ":", filename, sep =
""), width,  :
	unable to start device JPEG
In addition: Warning message: 
unable to open connection to X11 display`' 
Execution halted

Over CGI, running as webmstr and with no SetEnv command, I get:

Error in X11(paste("jpeg::", quality, ":", filename, sep =
""), width,  :
	unable to start device JPEG
In addition: Warning message: 
unable to open connection to X11 display`' 
Execution halted


Ahem... so I think the take home message is that I haven't a clue how X11
works or hy it is so awkward.  NOTE I HAVE THIS ALL WORKING ON MY LAPTOP which
is an identical setup.  I think what is telling is that the user webmstr
can't open X11 displays from R either through the command line or via CGI

Help?

Mick

Michael Watson
Head of Informatics
Institute for Animal Health,
Compton Laboratory,
Compton,
Newbury,
Berkshire RG20 7NN
UK

Phone : +44 (0)1635 578411 ext. 2535
Mobile: +44 (0)7764 490236
E-mail: michael.watson at bbsrc.ac.uk

Michael,

To create (most) chart types in batch mode or on a headless terminal, you
need to set up a 'virtual' X11 server.

This has become easier using the additional XFree86 'virtual framebuffer
server'. The package is called Xfvb, and your Linux distro will most likely
have it. You can also get it for Solaris and the other commercial unices.
With a bit of luck and google-ing, you should find some examples and howtos.

People who know more about security than I do advise against modifying xhost
settings at almost all costs.

Hth, Dirk

-- 
Don't drink and derive. Alcohol and analysis don't mix.