Zvol backed bhyve guest

Things have moved forward in the world of bhyve since I last looked at it over a year ago, support for zvol backed guests where fixed long ago among other things such as the birth of vmrc by Michael Dexter.
To run a guest with a ZFS zvol as its disk is no different to running with a disk image, only thing is that my version of /usr/share/examples/bhyve/vmrun.sh (11.0-CURRENT r267869 at the time of writing) fails to start from the disk once the OS has been installed.

A typical deployment scenario would be

Create a zvol of some size, e.g. 10GB

zfs create -V 10g zroot/guest0

Start a guest which’ll boot from the FreeBSD install CD iso & install onto the zvol

# sh /usr/share/examples/bhyve/vmrun.sh -c 4 -m 1024M -t tap0 -d /dev/zvol/zroot/guest0 -i -I FreeBSD-10.0-RELEASE-amd64-disc1.iso guest0

Use the “ZFS – Automatic Root-on-ZFS” option from the Partitioning menu

As instructed in the bhyve section of the handbook, before rebooting, drop to the shell & edit /etc/ttys & replace the console line with

console "/usr/libexec/getty std.9600" xterm on secure

Shutdown the operating system
halt -p

Kill the guest
/usr/sbin/bhyvectl --destroy --vm=guest0

Create a new guest
bhyveload -m 4G -d /dev/zvol/zroot/guest0 guest0

Boot the new guest from the zvol
bhyve -c 1 -m 4G -A -H -P -s0:0,hostbridge -s 1:0,virtio-net,tap0 -s 2:0,ahci-hd,/dev/zvol/zroot/guest0 -s 31,lpc -l com1,stdio guest0

These instruction skip the creation of networking which is covered in the FreeBSD handbook as linked to above.

Copyright (c) 1992-2014 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 10.0-RELEASE #0 r260789: Thu Jan 16 22:34:59 UTC 2014
root@snap.freebsd.org:/usr/obj/usr/src/sys/GENERIC amd64
FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610
CPU: Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz (3399.54-MHz K8-class CPU)
Origin = "GenuineIntel" Id = 0x306a9 Family = 0x6 Model = 0x3a Stepping = 9
AMD Features=0x20100800
AMD Features2=0x1
Standard Extended Features=0x200
TSC: P-state invariant
real memory = 5368709120 (5120 MB)
avail memory = 4103143424 (3913 MB)
Event timer "LAPIC" quality 400
ioapic0 irqs 0-23 on motherboard
random: initialized
module_register_init: MOD_LOAD (vesa, 0xffffffff80cfa5e0, 0) error 19
kbd1 at kbdmux0
acpi0: on motherboard
acpi0: Power Button (fixed)
atrtc0: port 0x70-0x71 irq 8 on acpi0
Event timer "HPET" frequency 10000000 Hz quality 550
Event timer "HPET1" frequency 10000000 Hz quality 450
Event timer "HPET2" frequency 10000000 Hz quality 450
Event timer "HPET3" frequency 10000000 Hz quality 450
Event timer "HPET4" frequency 10000000 Hz quality 450
Event timer "HPET5" frequency 10000000 Hz quality 450
Event timer "HPET6" frequency 10000000 Hz quality 450
Event timer "HPET7" frequency 10000000 Hz quality 450
Timecounter "ACPI-fast" frequency 3579545 Hz quality 900
acpi_timer0: port 0x408-0x40b on acpi0
pcib0: port 0xcf8-0xcff on acpi0
pci0: on pcib0
virtio_pci0: port 0x2000-0x201f mem 0xc0000000-0xc0001fff irq 16 at device 1.0 on pci0
vtnet0: on virtio_pci0
virtio_pci0: host features: 0x1018020
virtio_pci0: negotiated features: 0x18020
vtnet0: Ethernet address: 00:a0:98:7f:5a:41
virtio_pci1: port 0x2040-0x207f mem 0xc0002000-0xc0003fff irq 17 at device 2.0 on pci0
vtblk0: on virtio_pci1
virtio_pci1: host features: 0x10000044
virtio_pci1: negotiated features: 0x10000044
vtblk0: 40960MB (83886080 512 byte sectors)
isab0: at device 31.0 on pci0
isa0: on isab0
uart0: port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
uart0: console (9600,n,8,1)
uart1: port 0x2f8-0x2ff irq 3 on acpi0
sc0: at flags 0x100 on isa0
sc0: MDA
vga0: at port 0x3b0-0x3bb iomem 0xb0000-0xb7fff on isa0
atkbdc0: at port 0x60,0x64 on isa0
atkbd0: irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
ppc0: cannot reserve I/O port range
ZFS NOTICE: Prefetch is disabled by default if less than 4GB of RAM is present;
to enable, add "vfs.zfs.prefetch_disable=0" to /boot/loader.conf.
ZFS filesystem version: 5
ZFS storage pool version: features support (5000)
Timecounters tick every 10.000 msec
random: unblocking device.
Netvsc initializing... Timecounter "TSC-low" frequency 1699769676 Hz quality 1000
Trying to mount root from zfs:zroot/ROOT/default []...

2 Replies to “Zvol backed bhyve guest”

  1. Hi Sevan,

    Some suggestions:

    – when creating the zvol, the volmode property on the zvol to “dev” i.e. ‘-o volmode=dev’. This prevents the host from sniffing partitions, which can result in the install failing. Might not be an issue with a ZFS install, but certainly prevents MBF/UFS installs from completing.

    – the ttys edit isn’t quite right (it will result in a lot of syslog output). Instead, edit the “ttyu0” line instead of the “console” line, same changes. I’ll get in touch with Allan to update the handbook section.

    I saw on twitter that you had some issues with IPv6. Any more info on that ? Was v4 still working ?


  2. Hi Peter,
    Good to hear from you 🙂
    I hit that hurdle with the volmode setting, as I wasn’t aware of the setting, I assumed that I needed to use ZFS, thanks for the tip, that’ll makes a big difference as I’d rather use UFS on the guests.
    Regarding the IPv6 issue, IPv4 continues to work as normal but nothing on v6, only thing that’s logged to the console is in prompt_tty(): caught signal 2

Comments are closed.