question about semodule

[Sandra Julieta Rueda Rodriguez]

Hello,

I was playing with semodule (trying to understand how it works) so I added
a module. Later I also played with refpolicy and monolithic building
(again trying to understand how it works).

Now I want to delete the module I loaded before and this is the message I
am getting from the system:

# semodule -v -r KnockServer
Attempting to remove module 'KnockServer':
Ok: return value of 0.
Committing changes:
/usr/sbin/load_policy:  Can't load policy:  Invalid argument
libsemanage.semanage_reload_policy: load_policy returned error code 2.
/usr/sbin/load_policy:  Can't load policy:  Invalid argument
libsemanage.semanage_reload_policy: load_policy returned error code 2.
semodule:  Failed!

semodule -l works fine (apparently) and one of the items in the list is
KnockServer and its version.
Is there any way to know why semodule -r is failing? What argument is
invalid?

I have other questions about modules: what is the relationship between the
modules and the binary policy file installed at
/etc/selinux/(strict|targeted)/policy? Does this file include just base
modules? If so, where are the files for non-base modules stored? Is it
another binary file?

Thanks in advance,
Sandra