Libvirt NixOS Tests

A minimal set of NixOS integration tests for validating specific Libvirt features and supporting libvirt development.

These tests provide a convenient environment for:

• Running automated checks against Libvirt.
• Testing patches to virtualization backends (e.g., Cloud Hypervisor) by running the libvirt test suite in a reproducible NixOS VM environment.

Running Tests

These tests utilize the NixOS integration test framework (<nixpkgs>/nixos/lib/testing). Each test is a Bash script build by Nix and is available in interactive mode (attribute .driverInteractive) as well as in non-interactive mode (attribute .driver). For just running tests and seeing test results, the non-interactive mode is fine. For interactive debugging, please consider using the interactive mode. In interactive mode, you can type test_script() into the Python REPL to run the test cases.

Build and run the default set of test cases:

nix run -L .#tests.x86_64-linux.default.driver

Every test attribute also exposes a passthru attribute offering the test without enabling any port forwarding. This version is meant for the usage in the CI, where port forwarding could fail because of occupied ports.

nix run .\#tests.x86_64-linux.default.passthru.no_port_forwarding.driver

It might happen that the integration test runs out of resources when the user's tmp directory space is too small. You can try to mitigate this by setting XDG_RUNTIME_DIR=/tmp/libvirt before invoking the test script.

Available Tests

The libvirt-tests are divided into multiple tests suites, each leveraging the NixOS integration test framework. The NixOS tests are grouped by different factors, e.g. the longer running live migration tests are separated. Following test attributes are available. Each attribute can be run via nix run -L .#tests.x86_64-linux.<attribute>.driver.

• default
  • default test suite containing most of the tests
• live_migration
  • live migration tests that usually take longer to run
• hugepage
  • tests that require hugepages in the host VM to be available
• long_migration_with_load
  • long-running migration series with a VM that is under heavy memory load

Obtaining debug logs

To obtain debug logs from failing test cases automatically, set the DBG_LOG_DIR environment variable:

DBG_LOG_DIR="./logs" nix run .#tests.x86_64-linux.default.driver

After the run is over, you can find relevant Libvirt and Cloud Hypervisor logs in the DBG_LOG_DIR.

Using a Custom Libvirt or Cloud Hypervisor

To test against a specific version or local build, you should update your flake.nix to refer to the new input, for example:

libvirt-src.url = "git+file:/home/pschuster/dev/libvirt?submodules=1";

SSH into the VMs

To access the QEMU VMs, you can run

• ssh -o StrictHostKeyChecking=no root@localhost -p 2222 for the controllerVM, and
• ssh -o StrictHostKeyChecking=no root@localhost -p 3333 for the computeVM.

Inside one of those VMs, you can use

ssh -o StrictHostKeyChecking=no root@192.168.1.2

with password root to access the Cloud Hypervisor VM (testvm).

To directly access the Cloud Hypervisor VM, you can run

ssh -o StrictHostKeyChecking=no -J root@localhost:2222 root@192.168.1.2.

More Documentation

• VM networks overview