ZFSOnRoot - FreeBSD Wiki

You have an ad0 disk. Create one slice covering the entire disk: # fdisk -BI /dev/ad0 Initialize the BSDlabel: # bsdlabel -wB /dev/ad0s1 Edit your label and create a small (like 256MB-512MB) 'a' partition and use the rest for the 'd' partition: # bsdlabel -e /dev/ad0s1 Something like this will create 512MB 'a' partition and allocate the rest for the 'd' partition: # /dev/ad0s1: 8 partitions: #