The following method is a prerequisite for the success of your mod and your operating system version is matched, that succeeded before your mod. Say the extra prompt, mod in / lib / modules directory
insmod: ERROR: could not insert module dm-snapshot.ko: Unknown symbol in module
mod no problem, when the above problems, try the following:
modprobe modname insmod modname.ko
The principle of the above method, modprobe to load a dependent mod, but not entirely successful. insmod can finally run properly.