/etc/rc.conf
linux_enable=YES
rebootして、linux64 fdescfs linprocfs linsysfs tmpfs がロードされていることを確認
# kldstat Id Refs Address Size Name 1 63 0xffffffff80200000 1f3e2d0 kernel 2 1 0xffffffff82140000 59dfa8 zfs.ko 3 1 0xffffffff826de000 a4a0 cryptodev.ko 4 1 0xffffffff82b18000 3218 intpm.ko 5 1 0xffffffff82b1c000 2180 smbus.ko 6 1 0xffffffff82b1f000 3340 uhid.ko 7 1 0xffffffff82b23000 4350 ums.ko 8 1 0xffffffff82b28000 3380 usbhid.ko 9 1 0xffffffff82b2c000 31f8 hidbus.ko 10 1 0xffffffff82b30000 31a80 linux.ko 11 4 0xffffffff82b62000 be88 linux_common.ko 12 1 0xffffffff82b6e000 14b98 netlink.ko 13 1 0xffffffff82b83000 2dca0 linux64.ko 14 1 0xffffffff82bb1000 2260 pty.ko 15 1 0xffffffff82bb4000 3530 fdescfs.ko 16 1 0xffffffff82bb8000 73b0 linprocfs.ko 17 1 0xffffffff82bc0000 3284 linsysfs.ko
# kldload tmpfs kldload: can't load tmpfs: module already loaded or in kernel
Jail+zfsあたりを参照ください
# pkg install debootstrap