debian session

[Limer <ls...@ma...>]

Hi All,
Now that X is working, I installed a brand new system with gdm as default
session manager. But now I can not type my password to enter because the
keyboard layout is absolutely wrong. So I decided to install a base system
on another partition to access this partition and change this behavior. The
question is from where gdm is taking the keyboard layout ? 
If I put my WB in 1280x1024 (16bits) and launch bootstrap, I got in error
message saying not enough chip Ram, so I have to go back to 1152x900. No
chance to have a 1280x1024 WB and launch boot strap without having to
reboot with no startup-sequence ?
Thanks in advance
Lio