O2sim enviroment

Trying to run reconstruction on MC:
and got message:
Missing O2sim environment
How to fix it, please ?

aliBuild build O2sim --defaults o2 + alienv enter O2sim/latest then execution of $O2_ROOT/prodtests/full_system_test.sh

(if you use existing CVMFS installation or RPM packages… simply load the O2sim package)

@swenzel thanks. Yes, it works
In ,my alice dir I have two git repos (i.e. source codes): O2, O2Physics.
I compile three things:
aliBuild build O2 --defaults o2
aliBuild build O2Physics
aliBuild build O2sim --defaults o2
Can you , please, explain what is the relation between the three ?
Cheers, Roman.

O2sim is a meta package and contains everything you need to do MC processing.
It is sufficient to build O2sim, as this will also build O2 + O2Physics.

Thanks. I am developing O2.
Then each time I build O2sim it checks for the modifications in O2 sources (and O2Physics) ?
And if I rebuild just O2 shall O2sim use the new one ?