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Clint Shryock 9d0005e87e driver/qemu: Update docs, we use SHA256 not MD5
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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 SHA256 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_ports - (Optional) Ports on the guest machine that are listening for traffic from the host. These ports match up with any ReservedPorts requested in the Task specification

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

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 resources use is constrained by the Qemu hypervisor rather than the host kernel. VM network traffic still flows through the host's interface(s).