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* create plugin author guide; remove concepts/plugins * style guide; update links * update cni redirect * move host-volume plugin to /plugins/. Add arch host volume content. * Apply Jeff's style guide updates Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com> * Apply suggestions from code review Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com> * Create Base plugin API section, link to BasePlugin interface --------- Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com>
104 lines
3.8 KiB
Plaintext
104 lines
3.8 KiB
Plaintext
---
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layout: docs
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page_title: Configure the QEMU task driver
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description: Nomad's QEMU task driver provides a generic virtual machine runner that can execute any regular QEMU image. Review the QEMU task driver capabilities, plugin options, client requirements, and client attributes such as QEMU version. Learn how the QEMU task driver provides the highest level of workload isolation.
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---
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# Configure the QEMU task driver
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Name: `qemu`
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The `qemu` driver provides a generic virtual machine runner. QEMU can utilize
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the KVM kernel module to utilize hardware virtualization features and provide
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great performance. Currently the `qemu` driver can map a set of ports from the
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host machine to the guest virtual machine, and provides configuration for
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resource allocation.
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The `qemu` driver can execute any regular `qemu` image (e.g. `qcow`, `img`,
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`iso`), and is currently invoked with `qemu-system-x86_64`.
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The driver requires the image to be accessible from the Nomad client via the
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[`artifact` downloader](/nomad/docs/job-specification/artifact).
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## Capabilities
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The `qemu` driver implements the following [capabilities](/nomad/plugins/author/task-driver#capabilities-capabilities-error).
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| Feature | Implementation |
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| -------------------- | -------------- |
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| `nomad alloc signal` | false |
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| `nomad alloc exec` | false |
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| filesystem isolation | image |
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| network isolation | none |
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| volume mounting | none |
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## Client Requirements
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The `qemu` driver requires QEMU to be installed and in your system's `$PATH`.
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The task must also specify at least one artifact to download, as this is the only
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way to retrieve the image being run.
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## Client Attributes
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The `qemu` driver will set the following client attributes:
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- `driver.qemu` - Set to `1` if QEMU is found on the host node. Nomad determines
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this by executing `qemu-system-x86_64 -version` on the host and parsing the output
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- `driver.qemu.version` - Version of `qemu-system-x86_64`, ex: `2.4.0`
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Here is an example of using these properties in a job file:
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```hcl
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job "docs" {
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# Only run this job where the qemu version is higher than 1.2.3.
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constraint {
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attribute = "${driver.qemu.version}"
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operator = ">"
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value = "1.2.3"
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}
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}
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```
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## Plugin Options
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```hcl
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plugin "qemu" {
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config {
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image_paths = ["/mnt/image/paths"]
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args_allowlist = ["-drive", "-usbdevice"]
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}
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}
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```
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- `image_paths` (`[]string`: `[]`) - Specifies the host paths the QEMU
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driver is allowed to load images from.
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- `args_allowlist` (`[]string`: `[]`) - Specifies the command line
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flags that the [`args`] option is permitted to pass to QEMU. If
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unset, a job submitter can pass any command line flag into QEMU,
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including flags that provide the VM with access to host devices such
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as USB drives. Refer to the [QEMU documentation] for the available
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flags.
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## Resource Isolation
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Nomad uses QEMU to provide full software virtualization for virtual machine
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workloads. Nomad can use QEMU KVM's hardware-assisted virtualization to deliver
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better performance.
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Virtualization provides the highest level of isolation for workloads that
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require additional security, and resource use is constrained by the QEMU
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hypervisor rather than the host kernel. VM network traffic still flows through
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the host's interface(s).
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Note that the strong isolation provided by virtualization only applies
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to the workload once the VM is started. Operators should use the
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`args_allowlist` option to prevent job submitters from accessing
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devices and resources they are not allowed to access.
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## Next steps
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[Use the Java task driver in a job](/nomad/docs/job-declare/task-driver/qemu).
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[`args`]: /nomad/docs/job-declare/task-driver/qemu#args
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[QEMU documentation]: https://www.qemu.org/docs/master/system/invocation.html
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