kunit_tool How-To

What is kunit_tool?

kunit_tool is a script (tools/testing/kunit/kunit.py) that aids in building the Linux kernel as UML (User Mode Linux), running KUnit tests, parsing the test results and displaying them in a user friendly manner.

kunit_tool addresses the problem of being able to run tests without needing a virtual machine or actual hardware with User Mode Linux. User Mode Linux is a Linux architecture, like ARM or x86; however, unlike other architectures it compiles the kernel as a standalone Linux executable that can be run like any other program directly inside of a host operating system. To be clear, it does not require any virtualization support: it is just a regular program.

What is a .kunitconfig?

It’s just a defconfig that kunit_tool looks for in the base directory. kunit_tool uses it to generate a .config as you might expect. In addition, it verifies that the generated .config contains the CONFIG options in the .kunitconfig; the reason it does this is so that it is easy to be sure that a CONFIG that enables a test actually ends up in the .config.

How do I use kunit_tool?

If a kunitconfig is present at the root directory, all you have to do is:

./tools/testing/kunit/kunit.py run

However, you most likely want to use it with the following options:

./tools/testing/kunit/kunit.py run --timeout=30 --jobs=`nproc --all`
  • --timeout sets a maximum amount of time to allow tests to run.

  • --jobs sets the number of threads to use to build the kernel.


This command will work even without a .kunitconfig file: if no .kunitconfig is present, a default one will be used instead.

For a list of all the flags supported by kunit_tool, you can run:

./tools/testing/kunit/kunit.py run --help