sysbuild is a tool to automate the maintenance of the NetBSD sources and
the build of releases by means of a single command and a configuration
file that tells sysbuild what to do.

Since NetBSD 1.6 (released on July 2011), the source tree has included a
very flexible script (build.sh) to build a full NetBSD release for the
current platform or to cross-build for any of the supported platforms.

The flipside of the flexibility is that the script is inconvenient to use
on a daily basis because of the myriad of options it takes.  Furthermore,
managing the source trees that make up NetBSD is not in the scope of
build.sh: the user must fetch these trees and keep them up to date by hand.

While these details are all fine on their own, rebuilding NetBSD frequently
(to keep a system up to date, or just for development tasks) is convoluted.
Developers and users usually find themselves writing their own wrapper
scripts over build.sh to simplify their daily tasks.

sysbuild extends build.sh by adding support for configuration files and
source tree management, allowing NetBSD rebuilds with a single and simple
command.  Make sure to check the sysbuild-user package for a way to
trivially set up periodic NetBSD rebuilds under an dedicated, unprivileged
user.