Nomad
Configure the QEMU task 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
.
The driver requires the image to be accessible from the Nomad client via the
artifact
downloader.
Capabilities
The qemu
driver implements the following capabilities.
Feature | Implementation |
---|---|
nomad alloc signal | false |
nomad alloc exec | false |
filesystem isolation | image |
network isolation | none |
volume mounting | none |
Client Requirements
The qemu
driver requires QEMU to be installed and in your system's $PATH
.
The task must also specify at least one artifact to download, as this is the only
way to retrieve the image being run.
Client Attributes
The qemu
driver will set the following client attributes:
driver.qemu
- Set to1
if QEMU is found on the host node. Nomad determines this by executingqemu-system-x86_64 -version
on the host and parsing the outputdriver.qemu.version
- Version ofqemu-system-x86_64
, ex:2.4.0
Here is an example of using these properties in a job file:
job "docs" {
# Only run this job where the qemu version is higher than 1.2.3.
constraint {
attribute = "${driver.qemu.version}"
operator = ">"
value = "1.2.3"
}
}
Plugin Options
plugin "qemu" {
config {
image_paths = ["/mnt/image/paths"]
args_allowlist = ["-drive", "-usbdevice"]
}
}
image_paths
([]string
:[]
) - Specifies the host paths the QEMU driver is allowed to load images from.args_allowlist
([]string
:[]
) - Specifies the command line flags that theargs
option is permitted to pass to QEMU. If unset, a job submitter can pass any command line flag into QEMU, including flags that provide the VM with access to host devices such as USB drives. Refer to the QEMU documentation for the available flags.
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).
Note that the strong isolation provided by virtualization only applies
to the workload once the VM is started. Operators should use the
args_allowlist
option to prevent job submitters from accessing
devices and resources they are not allowed to access.