One issue I had while replacing FreeNAS with FreeBSD was that, by defualt, vnet support isn’t enabled in the kernel. To resolve this, I compiled a custom kernel as follows:

Step 1 - download the kernel sources

Change the FreeBSD version, as appropriate.

pkg install subversion
svn checkout http://svn.freebsd.org/base/release/10.2.0/ /usr/src

Step 2 - create a custom config

cd /usr/src/sys/amd64/conf # Replace amd64 with the desired architecture
cp GENERIC MYKERNEL

Once you’ve got a copy of the generic kernel configuration (MYKERNEL), make any required changes. In my case, I added the following, as per the instructions on the iocage README:

options         VIMAGE # VNET/Vimage support
options         RACCT  # Resource containers
options         RCTL   # same as above

Step 3 - build and install the kernel

cd /usr/src
make buildkernel KERNCONF=MYKERNEL
make installkernel KERNCONF=MYKERNEL

Let me know if you have any questions or… more importantly, if there’s an easier way of doing this!

Sources

Thanks to: