I want to upgrade to FreeBSD-12 Release, what is the best approach

[fd0]

*,

dc1# iocage -v
Version 0.9.10 2017/12/22
dc1# freebsd-version
11.2-RELEASE
dc1#

I'd like to upgrade to FreeBSD 12-RELEASE with the latest iocage.

I have several iocageVNET jails that have been working fine since install. What would be the best approach to upgrade to latest FreeBSD with latest iocage.

Would I run into trouble

-- fd0