Load and unload files into kernel

You can use kldload command to load files into kernel. For example, enter /boot/kernel directory, and use kldstat to check currently loaded files:

# cd /boot/kernel
# kldstat
Id Refs Address            Size     Name
 1    6 0xffffffff80200000 17bc6a8  kernel
 2    1 0xffffffff81a11000 56c6     fdescfs.ko
 3    1 0xffffffff81a17000 2ba8     uhid.ko

Use kldload to load zfs.ko file:

# kldload zfs.ko
# kldstat
Id Refs Address            Size     Name
 1   15 0xffffffff80200000 17bc6a8  kernel
 2    1 0xffffffff81a11000 56c6     fdescfs.ko
 3    1 0xffffffff81a17000 2ba8     uhid.ko
 7    1 0xffffffff81a1a000 1ee0c8   zfs.ko
 8    1 0xffffffff81c09000 3330     opensolaris.ko

You can see the zfs.ko is loaded successfully.

Unloading file uses kldunload command:

# kldunload zfs.ko
# kldstat
Id Refs Address            Size     Name
 1    6 0xffffffff80200000 17bc6a8  kernel
 2    1 0xffffffff81a11000 56c6     fdescfs.ko
 3    1 0xffffffff81a17000 2ba8     uhid.ko

Reference:
kldload;
kldunload.