I did a small table of found duplicates, the same question is: which modules are valid ?
+===========================+=========+===========+===========+
|    module_name            | modules | modules_k | modules_s |
+===========================+=========+===========+===========+
| acc_radius                |         |     x     |    x      |
| auth_db                   |         |     x     |    x      |
| auth_radius               |         |     x     |    x      |
| cpl-c                     |         |     x     |    x      |
| domain                    |         |     x     |    x      |
| exec                      |         |     x     |    x      |
| ldap                      |         |     x     |    x      |
| maxfwd                    |         |     x     |    x      |
| nathelper                 |         |     x     |    x      |
| permissions               |         |     x     |    x      |
| pike                      |         |     x     |    x      |
| registrar                 |         |     x     |    x      |
| rr                        |         |     x     |    x      |
| textops                   |         |     x     |    x      |
| uri_db                    |         |     x     |    x      |
| usrloc                    |         |     x     |    x      |
+===========================+=========+===========+===========+


2012/12/13 Konstantin M. <evilzluk@gmail.com>
Hello,

Looking to examples/exec.cfg I see:
loadmodule "modules/exec/exec.so"

but looking to files tree I see that 'exec' module is absent in modules but existing in modules_k and modules_s both.
Which one is a valid ?