how to jog dual gantry before homing

Hi,
I am new here, just rebuild an existing router and swapped the old electronics out for a mesa 7i96s with linuxcnc 2.9.4. everything went smooth except one thing.
The old router configuration had a single home sensor for a dual gantry. So i added an extra sensor for the second driver to be able to home. The problem is that it is impossible for me to add the sensor at the exact right spot (both are on opposite side of the machine.) So i managed to get the sensors roughly at the same spot (within 1mm) Now i would want to put the gantry manually square before powering up (it is a very sturdy bridge which automatically squares out if run by hand) and then i would like to power up the machine and jog incrementally up to the sensors. with the hal watch i could see which one lights up first and i could also check how much extra jogs i have to make to light up the other sensor. this would give me the offset i need to square out the bridge with homing. Now i am forcing the gantry out of square with the error in my sensor placement
SO here my queation: Is there a way to force linuxcnc to jog both joints simultaneous before homing

Maybe setup  a test ini file with immediate homing so no
home move is done and then you should be able to jog the
gantry axis after you hit the home-all button.

linuxcnc.org/docs/html/config/ini-homing.html#_configuration
 

the problem is i want to be able to jog the gantry before the home all, so i can find out what the physical misalignment of my sensors is. if i home first the homing will force my gantry according the sensors and so misalign my gantry and see it as homed and square

No, if you setup immediate homing, no home move or sensors are involved,
LinuxCNC simply takes the current position as home.

ok, thanks i check it out.
worked perfectly. 1,5mm difference. Is there a way to compensate for this directly in pncconf. the Y2 sensor is reached 1.5mm faster then Y, so Y2 should move 1.5mm further in the homing sequence?

HOME_OFFSET is used to manage squaring during homing. If there is 1.5mm difference per side, make the home offsets different by 1.5mm.
For initial squaring, I used a dial indicator and homed againt that. Probably a more accurate way is to home the machine and mark positions in each corner with a tool and adjust the home_offsets untill the measured diagonals are exactly identical.