Antti Kantee edited this page Jul 22, 2018 · 23 revisions

This page describes

The script builds unmodified NetBSD kernel drivers such as file systems and the TCP/IP stack as components which can be linked to form rump kernels. These lightweight rump kernels run on top of a high-level hypercall interface which is straightforward to implement for most environments. This repository includes the hypercall implementation for running in userspace on POSIX hosts, with alternative implementations such as for the Xen hypervisor being hosted elsewhere.

In other words, rump kernels enable embedding unmodified kernel drivers in various environments and using the drivers as services.

Rump kernels address the part of the software stack typically handled by an OS kernel. For running unmodified userspace applications against system call services provided by rump kernels, see rumpctrl.

Running requires a network connection for fetching NetBSD kernel driver source code. Self-contained archives can be created using the script, and snapshots are available for download from here.

Binary packages for userspace

Check the page binary packages to see if there packages for your platform.

Building from Source Code

Building from source may be necessary of there are no binary packages for your systems, or if you wish to make source level modifications to the rump kernel components.

Build dependencies

The following are required for building from source:

  • cc (gcc and clang are known to work)
  • ld (GNU or Solaris ld required)
  • binutils (ar, nm, objcopy)

The short version

Clone the repository and run:

  • ./

You will now find the kernel drivers and necessary headers in ./rump ready for use. Examples on how to use the resulting drivers are available in the tests directories.

The long(er) version

When run without parameters, implicitly assumes that the given commands were checkout fullbuild tests. You can override this default by giving explicit commands.

The checkout command will fetch the necessary subset of the NetBSD source tree from github into ./src (the location can be changed using the -s parameter). You are free to use any method for fetching NetBSD sources, though the only officially supported way is to use the checkout command. Note that the NetBSD sources and their timestamps may vary from one revision to another. By default, the script checks that you have the appropriate set of sources even if you do not run checkout.

The fullbuild command will then instruct the script to to build the necessary set of tools for building rump kernels, e.g. the BSD version of make, after which it will build the rump kernels. By default, cc from path is used along with other host tools such as nm. Crosscompilation is documented further below.

If the command tests is given, the script will run simple tests to check that e.g. file systems and the TCP/IP stack work correctly. If everything was successfully completed, the final output from the script is " ran successfully". Note that tests cannot be run when is used with a crosscompiler or in kernel-only mode (see below).

To learn more about command line parameters, run the script with the -h flag.


See Howto: Cross compiling.

Kernel-only mode

If the -k kernel-only parameter is specified, the script will omit building the POSIX hypercall implementation. This is useful if you are developing your own hypercall layer implementation. See the rumprun repository for the canonical example of using -k.

Setting compile flags

Normally will do a build with no special compiler flags other than optimisation flags (-O2). Mostly this will be fine, but if you are cross compiling or building for a specific architecture variant you can add additional flags using the -F option. For example -F CFLAGS='-march=m32 -mcpu=i586' will pass those options to the C compiler. As well as CFLAGS you can use AFLAGS and LDFLAGS, ACFLAGS to set both AFLAGS and CFLAGS and ACLFLAGS to set all three. You can repeat the -F option as many times as necessary. So for example to do a 32 bit build on a 64 bit host use ./ -F ACLFLAGS=-m32.

Note that not all CPU variants and ABIs are supported by NetBSD and the rump kernel, although a very large number are. The script does not warn about most potential issues.

Debug builds

The default build is a debug build (using -O2 -g, and enabling NetBSD assertions). You can increase debugginess with -D or more eg -DDD. If you want to customize the flags, use eg -F DBG='-O0 -g'. Using -r will do a release build, without debug symbols or assertions.

NetBSD build options

Options for the NetBSD build process can be specified using -V option=value.

Tips for advanced users

  • Place your buildtools in a separate directory, e.g. $HOME/rumptools using ./ -T $HOME/rumptools fullbuild. Put that directory in $PATH. You can now do fast build iteration for kernel components by going to the appropriate directory and running rumpmake dependall && rumpmake install.

  • You can list the NetBSD source dates used by ./ checkout by running ./ listdates.

  • Assuming you have a commit bit to NetBSD, you can use HEAD from NetBSD src and be able to commit your changes to NetBSD from src with the following setup:

    • ./ cvs nbcvs HEAD
    • ./ -s nbcvs fullbuild

    Of course, replace dev with your NetBSD account name. Equally "of course", this operating mode is not officially supported by However, if you run into problems that will affect after the checkout date is bumped, report the problems using your discretion.

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