two different xorg.conf and two X sessions in the same time

[maderios]

Hi
I usually launch 2 X sessions for two users in the same time.
I want  now two different xorg.conf for these users.
xorg.conf  :0    1280x1024
xorg2.conf  :1  1980x1440
  I created 2 files 
/var/log/Xorg2.1.log  et /var/log/Xorg2.1.log.old
Now I do in /etc/X11/
X  :1  -config  ./xorg2.conf  -logfile  /var/log/Xorg2.1.log
I get
Fatal server error
Cannot move old log file  ( " /var/log/Xorg2.1.log"  to " 
/var/log/Xorg2.1.log.old"

I tried too in /etc/X11/
X  :1  -config  ./xorg2.conf  -logfile  /home/user/Xorg2.1.log
I get 
Fatal server error :
xf860OpenConsole : Cannot open /dev/tty0 (not such a file or a directory)

I don't want to install any xsession like gdm

Thanks for any help
M