howto boot with a single gui app as the desktop ?

[Chris Mohler]

You could use ltsp terminals. The 'vnc-ltsp-config' package seems to
add VNC - I use ltsp with XDMCP at home.  It does pretty much what
you're describing, but it requires some configuration on the host
side.

Chris


yum info vnc-ltsp-config
Loading "installonlyn" plugin
Setting up repositories
Reading repository metadata in from local files
Available Packages
Name   : vnc-ltsp-config
Arch   : noarch
Version: 4.0
Release: 3
Size   : 4.8 k
Repo   : extras
Summary: Easy Enabler of VNC remote LTSP desktops
Description:
Easy Enabler of VNC remote LTSP desktops.  This package contains xinetd.d
configurations that allow incoming VNC clients to open a new desktop session
with each connection.  Xvnc connects to the local server using XDMCP.