A Virtual Machine (VM) is an environment on a host computer that can be used as if it were a separate physical computer. VMs can be used to run multiple operating systems simultaneously. Operating systems running inside a VM see emulated virtual hardware rather than the actual hardware of the host computer. This provides more isolation than Jails, although there is additional overhead. A portion of system RAM is assigned to each VM, and each VM uses a zvol for storage. While a VM is running, these resources are not available to the host computer or other VMs.
FreeNAS® VMs use the bhyve(8) virtual machine software. This type of virtualization requires an Intel processor with Extended Page Tables (EPT) or an AMD processor with Rapid Virtualization Indexing (RVI) or Nested Page Tables (NPT).
To verify that an Intel processor has the required features, use
Shell to run
grep VT-x /var/run/dmesg.boot. If the
EPT and UG features are shown, this processor can be used with
To verify that an AMD processor has the required features, use Shell to run grep POPCNT /var/run/dmesg.boot. If the output shows the POPCNT feature, this processor can be used with bhyve.
14.1. Creating VMs¶
VMs → Add VM for the Add VM dialog
VM configuration options are described in Table 14.1.1.
|Name||string||a name to identify the VM|
|Description||string||a short description of the VM or its purpose|
|Virtual CPUs||integer||quantity of virtual CPUs allocated to the VM, up to 16; although these are virtual and not strictly related to host processor cores, the host CPU might limit the maximum number; the operating system used in the VM might also have operational or licensing restrictions on the number of CPUs allowed|
|Memory Size (MiB)||integer||megabytes of RAM allocated to the VM|
|Boot Method||drop-down menu||UEFI for newer operating systems, or UEFI-CSM (Compatibility Support Mode) for older operating systems that only understand BIOS booting|
|Autostart||checkbox||start the VM automatically on boot|
14.2. Adding Devices to a VM¶
After creating the VM, click it to select it, then click the Devices button at the bottom of the screen to add virtual hardware to it:
VMs are given a NIC (Network Interface Card) by default. This interface emulates an Intel E1000 (82545) Ethernet card for compatibility with most operating systems:
The Adapter Type can be changed to VirtIO to provide better performance when the operating system installed in the VM supports VirtIO paravirtualized network drivers.
VMs set to UEFI booting are also given a VNC (Virtual Network Computing) remote connection:
A standard VNC client can connect to the VM to provide screen output and keyboard and mouse input. The VNC port number can be set to 0 or left empty for FreeNAS® to assign a port when the VM is started, or set to a fixed, preferred port number.
AHCI emulates an AHCI hard disk for best software compatibility. VirtIO uses paravirtualized drivers and can provide better performance, but requires the operating system installed in the VM to support VirtIO disk devices.
Adding a CD-ROM device makes it possible to boot the VM from a CD-ROM image, typically an installation CD. The image must be present on an accessible portion of the FreeNAS® storage. In this example, a FreeBSD installation image is shown:
VMs from other virtual machine systems can be recreated for use in FreeNAS®. Back up the original VM, then create a new FreeNAS® VM with virtual hardware as close as possible to the original VM. Binary-copy the disk image data into the zvol created for the FreeNAS® VM with a tool that operates at the level of disk blocks, like dd(1). For some VM systems, it is best to back up data, install the operating system from scratch in a new FreeNAS® VM, and restore the data into the new VM.
14.3. Running VMs¶
to see a list of configured VMs. Configuration and control buttons
appear at the bottom of the screen when an individual VM is selected
with a mouse click:
The name, description, running state, VNC port (if present), and other configuration values are shown. A Start button is shown when the VM is not running. Click this to start the VM. If a VNC port is present, use VNC client software to connect to that port for screen output and keyboard and mouse input.
On running VMs, the button is shown as Stop, and used, unsurprisingly, to stop them.