[root@emy-17 ~]# zoneadm -z b2 halt
[root@emy-17 ~]# zonecfg -z b2 info brand
brand: bhyve
[root@emy-17 ~]# uname -a
SunOS emy-17 5.11 joyent_20171230T062027Z i86pc i386 i86pc
[root@emy-17 ~]# zoneadm -z b2 boot; zlogin -C b2
Then grub appears
CentOS Linux (3.10.0) 7 (Core)
CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-bb78774b1c0041b990cc8f4d98bf19a1) 7 (Core)
Use the ^ and v keys to change the selection.
Press 'e' to edit the selected item, or 'c' for a command prompt.
And then we boot
[ 0.000000] Initializing cgroup subsys cpuset
[ 0.000000] Initializing cgroup subsys cpu
[ 0.000000] Initializing cgroup subsys cpuacct
[ 0.000000] Linux version 3.10.0 (mgerdts@b1) (gcc version 4.8.5 20150623 (Red Hat 4.8.5-16) (GCC) ) #6 SMP Thu Dec 28 17:49:21 CST 2017
[ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.10.0 root=/dev/mapper/centos-root ro crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap console=ttyS0
[ 0.000000] e820: BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009ffff] usable
[ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000beaa7fff] usable
[ 0.000000] BIOS-e820: [mem 0x00000000beaa8000-0x00000000beab8fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000beab9000-0x00000000bfb38fff] usable
[ 0.000000] BIOS-e820: [mem 0x00000000bfb39000-0x00000000bfb90fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bfb91000-0x00000000bfb98fff] ACPI data
[ 0.000000] BIOS-e820: [mem 0x00000000bfb99000-0x00000000bfb9cfff] ACPI NVS
[ 0.000000] BIOS-e820: [mem 0x00000000bfb9d000-0x00000000bffcffff] usable
[ 0.000000] BIOS-e820: [mem 0x00000000bffd0000-0x00000000bffeffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bfff0000-0x00000000bfffffff] usable
[ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000013fffffff] usable
[ 0.000000] NX (Execute Disable) protection: active
[ 0.000000] efi: EFI v2.40 by BHYVE
...