22.4. FreeBSD as a Host with bhyve

Starting with FreeBSD 10.0-RELEASE, the bhyve BSD-licensed hypervisor is part of the base system. This hypervisor supports a number of guests, including FreeBSD, OpenBSD, and many Linux® distributions. Currently, bhyve only supports a serial console and does not emulate a graphical console. As a legacy-free hypervisor, it relies on the virtualization offload features of newer CPUs, instead of translating instructions and manually managing memory mappings.

Due to the design of bhyve, it requires a computer with a newer processor that supports Intel® Extended Page Tables (EPT) or AMD® Rapid Virtualization Indexing (RVI), also known as Nested Page Tables (NPT). Most newer processors, specifically the Intel® Core™ i3/i5/i7 and Intel® Xeon™ E3/E5/E7, support this feature. For a complete list of Intel® processors that support EPT, refer to http://ark.intel.com/search/advanced?s=t&ExtendedPageTables=true. RVI is found on the 3rd generation and later of the AMD Opteron™ (Barcelona) processors. The easiest way to check for support of EPT or RVI is to look for the POPCNT processor feature flag on the Features2 line in dmesg or /var/run/dmesg.boot.

22.4.1. Preparing the Host

The first step to creating a virtual machine in bhyve is configuring the host system. First, load the bhyve kernel module:

# kldload vmm

Then, create a tap interface for the network device in the virtual machine to attach to. In order for the network device to participate in the network, also create a bridge interface containing the tap interface ane the physical interface as members. In this example, the physical interface is igb0:

# ifconfig tap0 create
# sysctl net.link.tap.up_on_open=1
net.link.tap.up_on_open: 0 -> 1
# ifconfig bridge0 create
# ifconfig bridge0 addm igb0 addm tap0
# ifconfig bridge0 up

22.4.2. Creating a FreeBSD Guest

Create a file to use as the virtual disk for the guest machine. Specify the size and name of the virtual disk:

# truncate -s 16G guest.img

Download an installation image of FreeBSD to install:

# fetch ftp://ftp.freebsd.org/pub/FreeBSD/ISO-IMAGES-amd64/10.0/FreeBSD-10.0-RELEASE-amd64-bootonly.iso
FreeBSD-10.0-RELEASE-amd64-bootonly.iso       100% of  209 MB  570 kBps 06m17s

FreeBSD comes with an example script for running a virtual machine in bhyve. The script will start the virtual machine and run it in a loop, so it will automatically restart if it crashes. The script takes a number of options to control the configuration of the machine: -c controls the number of virtual CPUs, -m limits the amount of memory available to the guest, -t defines which tap device to use, -d indicates which disk image to use, -i tells bhyve to boot from the CD image instead of the disk, and -I defines which CD image to use. The last parameter is the name of the virtual machine, used to track the running machines. This example starts the virtual machine in installation mode:

# sh /usr/share/examples/bhyve/vmrun.sh -c 4 -m 1024M -t tap0 -d guest.img -i -I FreeBSD-10.0-RELEASE-amd64-bootonly.iso guestname

The virtual machine will boot and start the installer. After installing a system in the virtual machine, when the system asks about dropping in to a shell at the end of the installation, choose Yes. A small change needs to be made to make the system start with a serial console. Edit /etc/ttys and replace the existing ttyu0 line with:

ttyu0   "/usr/libexec/getty 3wire"   xterm  on secure

Note:

Beginning with FreeBSD 9.3-RELEASE and 10.1-RELEASE the console is configured automatically.

Reboot the virtual machine. While rebooting the virtual machine causes bhyve to exit, the vmrun.sh script runs bhyve in a loop and will automatically restart it. When this happens, choose the reboot option from the boot loader menu in order to escape the loop. Now the guest can be started from the virtual disk:

# sh /usr/share/examples/bhyve/vmrun.sh -c 4 -m 1024M -t tap0 -d guest.img guestname

22.4.3. Creating a Linux® Guest

In order to boot operating systems other than FreeBSD, the sysutils/grub2-bhyve port must be first installed.

Next, create a file to use as the virtual disk for the guest machine:

# truncate -s 16G linux.img

Starting a virtual machine with bhyve is a two step process. First a kernel must be loaded, then the guest can be started. The Linux® kernel is loaded with sysutils/grub2-bhyve. Create a device.map that grub will use to map the virtual devices to the files on the host system:

(hd0) ./linux.img
(cd0) ./somelinux.iso

Use sysutils/grub2-bhyve to load the Linux® kernel from the ISO image:

# grub-bhyve -m device.map -r cd0 -M 1024M linuxguest

This will start grub. If the installation CD contains a grub.cfg, a menu will be displayed. If not, the vmlinuz and initrd files must be located and loaded manually:

grub> ls
(hd0) (cd0) (cd0,msdos1) (host)
grub> ls (cd0)/isolinux
boot.cat boot.msg grub.conf initrd.img isolinux.bin isolinux.cfg memtest
splash.jpg TRANS.TBL vesamenu.c32 vmlinuz
grub> linux (cd0)/isolinux/vmlinuz
grub> initrd (cd0)/isolinux/initrd.img
grub> boot

Now that the Linux® kernel is loaded, the guest can be started:

# bhyve -AI -H -P -s 0:0,hostbridge -s 1:0,lpc -s 2:0,virtio-net,tap1 -s 3:0,virtio-blk,./linux.img \
-s 4:0,ahci-cd,./somelinux.iso -l com1,stdio -c 4 -m 1024M linuxguest

The system will boot and start the installer. After installing a system in the virtual machine, reboot the virtual machine. This will cause bhyve to exit. The instance of the virtual machine needs to be destroyed before it can be started again:

# bhyvectl --destroy --vm=linuxguest

Now the guest can be started directly from the virtual disk. Load the kernel:

# grub-bhyve -m device.map -r hd0,msdos1 -M 1024M linuxguest
grub> ls
(hd0) (hd0,msdos2) (hd0,msdos1) (cd0) (cd0,msdos1) (host)
(lvm/VolGroup-lv_swap) (lvm/VolGroup-lv_root)
grub> ls (hd0,msdos1)/
lost+found/ grub/ efi/ System.map-2.6.32-431.el6.x86_64 config-2.6.32-431.el6.x
86_64 symvers-2.6.32-431.el6.x86_64.gz vmlinuz-2.6.32-431.el6.x86_64
initramfs-2.6.32-431.el6.x86_64.img
grub> linux (hd0,msdos1)/vmlinuz-2.6.32-431.el6.x86_64 root=/dev/mapper/VolGroup-lv_root
grub> initrd (hd0,msdos1)/initramfs-2.6.32-431.el6.x86_64.img
grub> boot

Boot the virtual machine:

# bhyve -AI -H -P -s 0:0,hostbridge -s 1:0,lpc -s 2:0,virtio-net,tap1 \
-s 3:0,virtio-blk,./linux.img -l com1,stdio -c 4 -m 1024M linuxguest

Linux® will now boot in the virtual machine and eventually present you with the login prompt. Login and use the virtual machine. When you are finished, reboot the virtual machine to exit bhyve. Destroy the virtual machine instance:

# bhyvectl --destroy --vm=linuxguest

22.4.4. Virtual Machine Consoles

It is advantageous to wrap the bhyve console in a session management tool such as sysutils/tmux or sysutils/screen in order to detach and reattach to the console. It is also possible to have the console of bhyve be a null modem device that can be accessed with cu. To do this, load the nmdm kernel module and replace -l com1,stdio with -l com1,/dev/nmdm0A. The /dev/nmdm devices are created automatically as needed, where each is a pair, corresponding to the two ends of the null modem cable (/dev/nmdm1A and /dev/nmdm1B). See nmdm(4) for more information.

# kldload nmdm
# bhyve -AI -H -P -s 0:0,hostbridge -s 1:0,lpc -s 2:0,virtio-net,tap1 -s 3:0,virtio-blk,./linux.img \
-l com1,/dev/nmdm0A -c 4 -m 1024M linuxguest
# cu -l /dev/nmdm0B -s 9600
Connected

Ubuntu 13.10 handbook ttyS0

handbook login:

22.4.5. Managing Virtual Machines

A device node is created in /dev/vmm for each virtual machine. This allows the administrator to easily see a list of the running virtual machines:

# ls -al /dev/vmm
total 1
dr-xr-xr-x   2 root  wheel    512 Mar 17 12:19 ./
dr-xr-xr-x  14 root  wheel    512 Mar 17 06:38 ../
crw-------   1 root  wheel  0x1a2 Mar 17 12:20 guestname
crw-------   1 root  wheel  0x19f Mar 17 12:19 linuxguest
crw-------   1 root  wheel  0x1a1 Mar 17 12:19 otherguest

A specified virtual machine can be destroyed using bhyvectl:

# bhyvectl --destroy --vm=guestname

22.4.6. Persistent Configuration

In order to configure the system to start bhyve guests at boot time, add the following entries to in the following files:

  1. /etc/sysctl.conf

    net.link.tap.up_on_open=1
  2. /boot/loader.conf

    vmm_load="YES"
    nmdm_load="YES"
    if_bridge_load="YES"
    if_tap_load="YES"
  3. /etc/rc.conf

    cloned_interfaces="bridge0 tap0"
    ifconfig_bridge0="addm igb0 addm tap0"

All FreeBSD documents are available for download at http://ftp.FreeBSD.org/pub/FreeBSD/doc/

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