I am using kamailio with ubuntu, but I can't obtain CDRs.

In my conf. file related to CDR I have:

modparam("acc", "cdr_enable", 1)
modparam("acc", "cdr_start_on_confirmed", 1)
modparam("acc", "cdrs_table", "acc_cdrs")
modparam("acc", "cdr_start_id", "start_time")
modparam("acc", "cdr_end_id", "end_time")
modparam("acc", "cdr_duration_id", "duration")

But I don't know where is the problem.

Regards