nomad/website/source/docs/drivers/qemu.html.md

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docs	Drivers: Qemu	docs-drivers-qemu	The Qemu task driver is used to run virtual machines using Qemu/KVM.

Qemu Driver

Name: qemu

The Qemu driver provides a generic virtual machine runner. Qemu can utilize the KVM kernel module to utilize hardware virtualization features and provide great performance. Currently the Qemu driver can map a set of ports from the host machine to the guest virtual machine, and provides configuration for resource allocation.

The Qemu driver can execute any regular qemu image (e.g. qcow, img, iso), and is currently invoked with qemu-system-x86_64.

Task Configuration

The Qemu driver supports the following configuration in the job spec:

• image_source - (Required) The hosted location of the source Qemu image. Must be accessible from the Nomad client, via HTTP.
• checksum - (Required) The MD5 checksum of the qemu image. If the checksums do not match, the Qemu diver will fail to start the image
• accelerator - (Optional) The type of accelerator to use in the invocation. If the host machine has Qemu installed with KVM support, users can specify kvm for the accelerator. Default is tcg
• host_port - (Required) Port on the host machine to forward to the guest VM
• guest_port - (Required) Port on the guest machine that is listening for traffic from the host

Client Requirements

The Qemu driver requires Qemu to be installed and in your systems $PATH. The image_source must be accessible by the node running Nomad. This can be an internal source, private to your cluster, but it must be reachable by the client over HTTP.

Client Attributes

The Qemu driver will set the following client attributes:

• driver.qemu - Set to 1 if Qemu is found on the host node. Nomad determines this by executing qemu-system-x86_64 -version on the host and parsing the output
• driver.qemu.version - Version of qemu-system-x86_64, ex: 2.4.0`

Resource Isolation

The resource isolation provided varies by the operating system of the client and the configuration.

On Linux, Nomad will attempt to use cgroups, namespaces, and chroot to isolate the resources of a process. If the Nomad agent is not running as root many of these mechanisms cannot be used.

As a baseline, the Qemu images will be ran inside a virtual machine operated by Qemu, providing a minimum amount of isolation.