gpart create -s gpt /dev/ada1
gpart add -b 128 -t freebsd-swap -s 2G /dev/ada1
gpart add -t freebsd-zfs /dev/ada1
Run zpool status and note the gptid of the existing disk
Run gpart list and find the gptid of the newly created partition. It is the rawuuid field. In this example it would be rawuuid of ada1p1
zpool attach tank /dev/gptid/[gptid_of_the_existing_disk] /dev/gptid/[gptid_of_the_new_partition]

where

• /dev/ada1 is the new disk.
• tank is the pool name.