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

layout	page_title	sidebar_current	description
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:

• artifact_source - (Required) The hosted location of the source Qemu image. Must be accessible from the Nomad client, via HTTP.
• checksum - (Optional) The checksum type and value for the artifact_source image. The format is type:value, where type is any of md5, sha1, sha256, or sha512, and the value is the computed checksum. If a checksum is supplied and does not match the downloaded artifact, the driver will fail to start
• 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
• port_map - (Optional) A map[string]int that maps port labels to ports on the guest. This forwards the host port to the guest vm. For example, port_map { db = 6539 } would forward the host port with label db to the guest vm's port 6539.

Client Requirements

The Qemu driver requires Qemu to be installed and in your system's $PATH. The artifact_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

Nomad uses Qemu to provide full software virtualization for virtual machine workloads. Nomad can use Qemu KVM's hardware-assisted virtualization to deliver better performance.

Virtualization provides the highest level of isolation for workloads that require additional security, and resource use is constrained by the Qemu hypervisor rather than the host kernel. VM network traffic still flows through the host's interface(s).