build.sh
Table of Contents
NetBSD uses a framework, build.sh,
to build both the operating system's kernel and the whole userland
for either the same platform as the host machine, or for a different
platform, using cross-compilation.
build.sh will take care of creating all the
tools required to build NetBSD for a given platform, and make them
available ready to use for development work.
In this chapter, we will show how to use
build.sh to first create a toolchain,
including compiler, assembler, linker and so on,
then use it to cross-compile a NetBSD kernel and userspace for
AArch64 on an AMD64 host machine.
While native kernel builds are covered in Chapter 34, Compiling the kernel, using the build.sh
script is generally preferred for building the entire of NetBSD.
Before starting, we have placed the sources in a subdirectory
of our user's home directory: /home/nia/cvs/src.
While /usr/src is the traditional location for
NetBSD sources, as described in
Chapter 32, Obtaining the sources, we would like to build the operating
system as an unprivileged (non-root) user.
A more detailed description of the build.sh
framework can be found in Luke Mewburn and Matthew Green's
paper
and their
presentation
from BSDCon 2003 as well as in
/usr/src/BUILDING.
The first step to do cross-development is to get all the necessary tools available. In NetBSD terminology, this is called the "toolchain", and it includes BSD-compatible make(1), C/C++ compilers, linker, assembler, config(8), as well as a fair number of tools that are only required when crosscompiling a full NetBSD release, which we won't cover here.
The command to create the toolchain is quite simple, using
NetBSD's src/build.sh script. Please note
that all the commands here can be run as normal (non-root) user:
$cd /home/nia/cvs/src$./build.sh -U -O ~/obj -j2 -m evbarm -a aarch64 tools
The "-U" option indicates we are doing an unprivileged build,
as a non-root user, typically with the source code located somewhere
other than /usr/src
The "-O" option specifies the directory to use for compiled object files.
The "-j2" option specifies the number of parallel builds to run. You may wish to set this to the number of CPU cores on your host system.
The "-m evbarm -a aarch64" options indicate we are building for a machine type of evbarm with a CPU type of aarch64. You can list the available machines and CPU types:
$./build.sh list-arch
If the tools have been built previously and they only need to be updated, then the update option "-u" can be used to only rebuild tools that have changed:
$./build.sh -U -u -O ~/obj -j2 -m evbarm -a aarch64 tools
When the tools are built, information about them and several environment variables is printed out:
===> Tools built to /home/nia/obj/tooldir.NetBSD-9.99.81-amd64 ===> build.sh ended: Sun Apr 18 12:10:58 CEST 2021 ===> Summary of results: build.sh command: ./build.sh -U -u -O /home/nia/obj -j2 -m evbarm -a aarch64 tools build.sh started: Sun Apr 18 11:17:46 CEST 2021 NetBSD version: 9.99.81 MACHINE: evbarm MACHINE_ARCH: aarch64 Build platform: NetBSD 9.99.81 amd64 HOST_SH: /bin/sh No $TOOLDIR/bin/nbmake, needs building. Bootstrapping nbmake MAKECONF file: /etc/mk.conf TOOLDIR path: /home/nia/obj/tooldir.NetBSD-9.99.81-amd64 DESTDIR path: /home/nia/obj/destdir.evbarm RELEASEDIR path: /home/nia/obj/releasedir Created /home/nia/obj/tooldir.NetBSD-9.99.81-amd64/bin/nbmake Updated makewrapper: /home/nia/obj/tooldir.NetBSD-9.99.81-amd64/bin/nbmake-evbarm Tools built to /home/nia/obj/tooldir.NetBSD-9.99.81-amd64 build.sh ended: Sun Apr 18 12:10:58 CEST 2021
During the build, object directories are used consistently, i.e. special directories are kept that keep the platform-specific object files and compile results. In our example, they will be kept in directories named "obj.evbarm" as we build for AArch64 as target platform.
The toolchain itself is part of this, but as it's hosted and compiled for an amd64 system, it will get placed in its own directory indicating where to cross-build from. Here's where our toolchain is located:
$pwd/home/nia/cvs/src$ls -d ~/obj/tooldir*/home/nia/obj/tooldir.NetBSD-9.99.81-amd64
So, the general rule of thumb is for a given "host" and "target" system combination, the cross-compiler will be placed in the "tooldir.host" directory by default. A full list of all tools created for cross-compiling the whole NetBSD operating system includes:
$ls ~/obj/tooldir.NetBSD-9.99.81-amd64/binaarch64--netbsd-addr2line nbconfig nbmkcsmapper aarch64--netbsd-ar nbcrunchgen nbmkdep aarch64--netbsd-as nbctags nbmkesdb aarch64--netbsd-c++ nbctfconvert nbmklocale aarch64--netbsd-c++filt nbctfmerge nbmknod aarch64--netbsd-cpp nbcvslatest nbmktemp aarch64--netbsd-dbsym nbdb nbmkubootimage aarch64--netbsd-elfedit nbdisklabel nbmsgc aarch64--netbsd-fdisk nbdtc nbmtree aarch64--netbsd-g++ nbeqn nbnroff aarch64--netbsd-gcc nbfile nbpax aarch64--netbsd-gcc-9.3.0 nbgenassym nbpaxctl aarch64--netbsd-gcc-ar nbgencat nbperf aarch64--netbsd-gcc-nm nbgmake nbpic aarch64--netbsd-gcc-ranlib nbgpt nbpwd_mkdb aarch64--netbsd-gcov nbgrep nbrefer aarch64--netbsd-gcov-dump nbgroff nbrpcgen aarch64--netbsd-gcov-tool nbhexdump nbsed aarch64--netbsd-install nbhost-mkdep nbslc aarch64--netbsd-ld nbindxbib nbsoelim aarch64--netbsd-ld.bfd nbinstall-info nbsortinfo aarch64--netbsd-mdsetimage nbinstallboot nbstat aarch64--netbsd-nm nbjoin nbstrfile aarch64--netbsd-objcopy nblex nbsunlabel aarch64--netbsd-objdump nbllvm-tblgen nbtbl aarch64--netbsd-ranlib nblorder nbtexi2dvi aarch64--netbsd-readelf nbm4 nbtexi2pdf aarch64--netbsd-size nbmake nbtexindex aarch64--netbsd-strings nbmake-evbarm nbtic aarch64--netbsd-strip nbmakefs nbtsort nbasn1_compile nbmakeinfo nbuudecode nbawk nbmakekeys nbxz nbcap_mkdb nbmakestrs nbyacc nbcat nbmakewhatis nbzic nbcksum nbmandoc nbcompile_et nbmenuc
As you can see, most of the tools that are available native on NetBSD are present with some program prefix to identify the target platform for tools that are specific to a certain target platform.
One important tool that should be pointed out here is "nbmake-evbarm". This is a shell wrapper for a BSD compatible make(1) command that's setup to use all the right commands from the cross-compilation toolchain. Using this wrapper instead of /usr/bin/make allows crosscompiling programs that were written using the NetBSD Makefile infrastructure (see src/share/mk). We will use this make(1) wrapper in a second to cross compile the kernel!
Now that we have a working toolchain available, the "usual" steps for building a kernel are needed - create a kernel config file, run config(1), then build. As the config(1) program used to create header files and Makefile for a kernel build is platform specific, we need to use the "nbconfig" program that's part of our new toolchain. That aside, the procedure is just as like compiling a "native" NetBSD kernel. Commands involved here are:
$cd /home/nia/cvs/src/sys/arch/evbarm/conf$cp GENERIC64MYKERNEL$viMYKERNEL$/home/nia/obj/tooldir.NetBSD-9.99.81-amd64/bin/nbconfigMYKERNEL
That's all. This command has created a directory
../compile/
with a number of header files defining information about devices
to compile into the kernel, a Makefile that is setup to build
all the needed files for the kernel, and link them together.MYKERNEL
We have all the files and tools available to crosscompile our
AArch64-based kernel from our Intel-based host system, so
let's get to it! After changing in the directory created in the
previous step, we need to use the toolchain's
nbmake-evbarm shell wrapper, which just
calls make(1) with all the necessary settings for crosscompiling
for an AArch64 platform:
$cd ../compile/MYKERNEL/$/home/nia/obj/tooldir.NetBSD-9.99.81-amd64/bin/nbmake-evbarm depend$/home/nia/obj/tooldir.NetBSD-9.99.81-amd64/bin/nbmake-evbarm
This will churn away a bit, then spit out a kernel:
... text data bss dec hex filename 11131832 3627920 1738912 16498664 fbbfe8 netbsd ...$ls -lh netbsd-rwxr-xr-x 1 nia wheel 16M Apr 18 12:46 netbsd$file netbsdnetbsd: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, for NetBSD 9.99.81, not stripped
Since we are building for AArch64, a few other kernel images
in different formats were built, including netbsd.img
and netbsd.bin for the U-Boot /boot
partition. On systems with more standard boot procedures, you only need to
worry about netbsd.
Now the kernel in the file netbsd can
be transferred to a machine (via scp, rsync, etc.) and booted.
After configuring and crosscompiling the kernel, the next
logical step is to crosscompile the whole system, and bring it
into a distribution-ready format. Before doing so, an
alternative approach to crosscompiling a kernel will be shown
in the next section, using the build.sh
script to do configuration and crosscompilation of the kernel
in one step.
build.sh
A cross compiled kernel can be done manually as described in
the previous sections, or by the easier method of using
build.sh, which will be shown here.
Preparation of the kernel config file is the same as described above:
$cd /home/nia/cvs/src/sys/arch/evbarm/conf$cp GENERIC64MYKERNEL$viMYKERNEL
Then edit MYKERNEL and once finished,
all that needs to be done is
to use build.sh to build the kernel
(it will also configure it, running the steps shown above):
$cd /home/nia/cvs/src$./build.sh -U -u -j2 -O ~/obj -m evbarm -a aarch64 kernel=MYKERNEL
Notice that update ("-u") was specified, the tools are
already built, there
is no reason to rebuild all of the tools. Once the kernel is built,
build.sh will print its location,
along with other information:
... ===> Summary of results: build.sh command: ./build.sh -O /home/nia/obj -U -u -j2 -m evbarm -a aarch64 kernel=MYKERNEL build.sh started: Sun Apr 18 12:25:16 CEST 2021 NetBSD version: 9.99.81 MACHINE: evbarm MACHINE_ARCH: aarch64 Build platform: NetBSD 9.99.81 amd64 HOST_SH: /bin/sh MAKECONF file: /etc/mk.conf TOOLDIR path: /home/nia/obj/tooldir.NetBSD-9.99.81-amd64 DESTDIR path: /home/nia/obj/destdir.evbarm RELEASEDIR path: /home/nia/obj/releasedir Updated makewrapper: /home/nia/obj/tooldir.NetBSD-9.99.81-amd64/bin/nbmake-evbarm Building kernel without building new tools Building kernel: MYKERNEL Build directory: /home/nia/obj/sys/arch/evbarm/compile/MYKERNEL Kernels built from MYKERNEL: /home/nia/obj/sys/arch/evbarm/compile/MYKERNEL/netbsd build.sh ended: Sun Apr 18 12:46:26 CEST 2021 ===> .
The path to the kernel built is of interest here:
/home/nia/obj/sys/arch/evbarm/compile/,
it can be used the same way as described above.MYKERNEL/netbsd
By now it is probably becoming clear that the toolchain actually
works in stages. First the toolchain is built, then a
kernel. Since build.sh will attempt to
rebuild the tools at every invocation, using "update"
saves time. It is probably also clear that outside of a few options,
the build.sh semantics are basically
build.sh command.
So, it stands to reason that
building the whole userland and/or a release is a matter of
using the right commands.
It should be no surprise that building and creating a release would look like the following:
$./build.sh -U -u -j2 -O ~/obj -m evbarm -a aarch64 release
These commands will compile the full NetBSD userland and put it into the destination object directory, and then build a release from it in a release subdirectory.
The NetBSD project has its own copy of the X Window System's which contains changes to make X function well on as many of the platforms supported by NetBSD as possible. Due to this, it is desirable to use the X Window System version available from and for NetBSD, which can also be crosscompiled much like the kernel and base system. To do so, the "xsrc" sources must be checked out from CVS into just as "src" and "pkgsrc" were as described in Chapter 32, Obtaining the sources.
After this, X can be crosscompiled for the target platform by
adding the -x switch to build.sh, e.g. when creating
a full release:
$./build.sh -U -u -O ~/obj -j2 -x -X /home/nia/cvs/xsrc -m evbarm -a aarch64 release
The -x option automatically sets
the variable to build X11, and -X
points to the directory containing the X11 sources.
The build system has a lot of variables that can be used to direct
things like where certain files go, what (if any) tools are used
and so on. A look in src/BUILDING covers
most of them. In this section some examples of changing default
settings are given, each following its own ways.
Many people like to track NetBSD-current and perform cross compiles of architectures that they use. The logic for this is simple, sometimes a new feature or device becomes available and someone may wish to use it. By keeping track of changes and building every now and again, one can be assured that these architectures can build their own release.
It is reasonable to assume that if one is tracking and building for more than one architecture, they might want to keep the builds in a different location than the default. There are two ways to go about this, either use a script to set the new DESTDIR, or simply do so interactively. In any case, it can be set the same way as any other variable (depending on your shell of course).
For sh(1), or ksh(1), this is:
$export DESTDIR=/usr/builds/evbarm-aarch64
For csh(1), the command is:
$setenv DESTDIR /usr/builds/evbarm-aarch64
Simple enough. When the build is run, the binaries and
files will be sent to /usr/builds.
The NetBSD toolchain builds and links against shared libraries
by default. Many users still prefer to be able to link
statically. Sometimes a small system can be created without
having shared libraries, which is a good example of doing a
full static build. If a particular build machine will always
need one environment variable set in a particular way, then it
is easiest to simply add the changed setting to
/etc/mk.conf.
To make sure a build box always builds statically, simply
add the following line to
/etc/mk.conf:
LDSTATIC=-static
build.sh optionsBesides variables in environment and
/etc/mk.conf, the build process can be
influenced by a number of switches to the
build.sh script itself, as we have
already seen when forcing unprivileged (non-root) builds,
selecting the target architecture or preventing deletion of
old files before the build. All these options can be
listed by running build.sh -h:
$cd /home/nia/cvs/src$build.sh -hUsage: build.sh [-EhnoPRrUuxy] [-a arch] [-B buildid] [-C cdextras] [-c compiler] [-D dest] [-j njob] [-M obj] [-m mach] [-N noisy] [-O obj] [-R release] [-S seed] [-T tools] [-V var=[value]] [-w wrapper] [-X x11src] [-Y extsrcsrc] [-Z var] operation [...] Build operations (all imply "obj" and "tools"): build Run "make build". distribution Run "make distribution" (includes DESTDIR/etc/ files). release Run "make release" (includes kernels & distrib media). Other operations: help Show this message and exit. makewrapper Create nbmake-${MACHINE} wrapper and nbmake. Always performed. cleandir Run "make cleandir". [Default unless -u is used] dtb Build devicetree blobs. obj Run "make obj". [Default unless -o is used] tools Build and install tools. install=idir Run "make installworld" to `idir' to install all sets except `etc'. Useful after "distribution" or "release" kernel=conf Build kernel with config file `conf' kernel.gdb=conf Build kernel (including netbsd.gdb) with config file `conf' releasekernel=conf Install kernel built by kernel=conf to RELEASEDIR. kernels Build all kernels installmodules=idir Run "make installmodules" to `idir' to install all kernel modules. modules Build kernel modules. rumptest Do a linktest for rump (for developers). sets Create binary sets in RELEASEDIR/RELEASEMACHINEDIR/binary/sets. DESTDIR should be populated beforehand. distsets Same as "distribution sets". sourcesets Create source sets in RELEASEDIR/source/sets. syspkgs Create syspkgs in RELEASEDIR/RELEASEMACHINEDIR/binary/syspkgs. iso-image Create CD-ROM image in RELEASEDIR/images. iso-image-source Create CD-ROM image with source in RELEASEDIR/images. live-image Create bootable live image in RELEASEDIR/RELEASEMACHINEDIR/installation/liveimage. install-image Create bootable installation image in RELEASEDIR/RELEASEMACHINEDIR/installation/installimage. disk-image=target Create bootable disk image in RELEASEDIR/RELEASEMACHINEDIR/binary/gzimg/target.img.gz. params Display various make(1) parameters. list-arch Display a list of valid MACHINE/MACHINE_ARCH values, and exit. The list may be narrowed by passing glob patterns or exact values in MACHINE or MACHINE_ARCH. Options: -a arch Set MACHINE_ARCH to arch. [Default: deduced from MACHINE] -B buildid Set BUILDID to buildid. -C cdextras Append cdextras to CDEXTRA variable for inclusion on CD-ROM. -c compiler Select compiler: clang gcc [Default: gcc] -D dest Set DESTDIR to dest. [Default: destdir.MACHINE] -E Set "expert" mode; disables various safety checks. Should not be used without expert knowledge of the build system. -h Print this help message. -j njob Run up to njob jobs in parallel; see make(1) -j. -M obj Set obj root directory to obj; sets MAKEOBJDIRPREFIX. Unsets MAKEOBJDIR. -m mach Set MACHINE to mach. Some mach values are actually aliases that set MACHINE/MACHINE_ARCH pairs. [Default: deduced from the host system if the host OS is NetBSD] -N noisy Set the noisyness (MAKEVERBOSE) level of the build: 0 Minimal output ("quiet") 1 Describe what is occurring 2 Describe what is occurring and echo the actual command 3 Ignore the effect of the "@" prefix in make commands 4 Trace shell commands using the shell's -x flag [Default: 2] -n Show commands that would be executed, but do not execute them. -O obj Set obj root directory to obj; sets a MAKEOBJDIR pattern. Unsets MAKEOBJDIRPREFIX. -o Set MKOBJDIRS=no; do not create objdirs at start of build. -P Set MKREPRO and MKREPRO_TIMESTAMP to the latest source CVS timestamp for reproducible builds. -R release Set RELEASEDIR to release. [Default: releasedir] -r Remove contents of TOOLDIR and DESTDIR before building. -S seed Set BUILDSEED to seed. [Default: NetBSD-majorversion] -T tools Set TOOLDIR to tools. If unset, and TOOLDIR is not set in the environment, nbmake will be (re)built unconditionally. -U Set MKUNPRIVED=yes; build without requiring root privileges, install from an UNPRIVED build with proper file permissions. -u Set MKUPDATE=yes; do not run "make cleandir" first. Without this, everything is rebuilt, including the tools. -V var=[value] Set variable `var' to `value'. -w wrapper Create nbmake script as wrapper. [Default: ${TOOLDIR}/bin/nbmake-${MACHINE}] -X x11src Set X11SRCDIR to x11src. [Default: /usr/xsrc] -x Set MKX11=yes; build X11 from X11SRCDIR -Y extsrcsrc Set EXTSRCSRCDIR to extsrcsrc. [Default: /usr/extsrc] -y Set MKEXTSRC=yes; build extsrc from EXTSRCSRCDIR -Z var Unset ("zap") variable `var'.
As can be seen, a number of switches can be set to change the standard build behaviour. A number of them has already been introduced, others can be set as appropriate.
Several variables control the behaviour of NetBSD builds.
Unless otherwise specified, these variables may be set in
either the process environment or in the make(1)
configuration file specified by MAKECONF.
For a definitive list of these options, see
BUILDING and
share/mk/bsd.README files in the
toplevel source directory.
Identifier for the build. The identifier will be appended to object directory names, and can be consulted in the make(1) configuration file in order to set additional build parameters, such as compiler flags.
Directory to contain the built NetBSD system. If set, special
options are passed to the compilation tools to prevent their
default use of the host system's
/usr/include,
/usr/lib, and so forth. This pathname
should not end with a slash (/) character (For installation
into the system's root directory, set DESTDIR
to an empty string). The directory must reside on a filesystem
which supports long filenames and hard links.
Defaults to an empty string if USETOOLS is
"yes"; unset otherwise. Note:
build.sh will provide a default
(destdir.MACHINE in the top-level .OBJDIR)
unless run in "expert" mode.
If defined by the user, points to the root of an
external toolchain (e.g.
/usr/local/gnu). This enables
the cross-build framework even when default toolchain
is not available (see TOOLCHAIN_MISSING
below).
Default: Unset
The verbosity of build messages. Supported values:
Default: 2
Can be set to "yes" or "no". Indicates whether preformatted plaintext manual pages will be created during a build.
Default: "yes"
Can be set to "yes" or "no". Indicates
whether system documentation destined for
DESTDIR/usr/share/doc will
be installed during a build.
Default: "yes"
Can be set to "yes" or "no". If set to "yes", then for programs intended to be run on the compile host, the name, release and architecture of the host operating system will be suffixed to the name of the object directory created by "make obj". This allows for multiple host systems to compile NetBSD for a single target. If set to "no", then programs built to be run on the compile host will use the same object directory names as programs built to be run on the target.
Default: "no"
Can be set to "yes" or "no". Indicates whether GNU info files, used for the documentation of most of the compilation tools, will be created and installed during a build.
Default: "yes"
Can be set to "yes" or "no". Indicates
whether lint(1) will be run against portions of the NetBSD
source code during the build, and whether lint libraries will
be installed into
DESTDIR/usr/libdata/lint
Default: "yes"
Can be set to "yes" or "no". Indicates whether manual pages will be installed during a build.
Default: "yes"
Can be set to "yes" or "no". Indicates whether Native Language System locale zone files will be compiled and installed during a build.
Default: "yes"
Can be set to "yes" or "no". Indicates whether object directories will be created when running "make obj". If set to "no", then all built files will be located inside the regular source tree.
Default: "yes"
Can be set to "yes" or "no". Indicates whether shared objects and libraries will be created and installed during a build. If set to "no", the entire build will be statically linked.
Default: Platform dependent. As of this writing, all platforms except sh3 default to "yes"
Can be set to "yes" or "no". Indicates
whether the ar(1) format libraries
(lib*_pic.a), used to generate shared
libraries, are installed during a build.
Default: "yes"
Can be set to "yes" or "no". Indicates
whether profiled libraries (lib*_p.a)
will be built and installed during a build.
Default: "yes"; however, some platforms turn off
MKPROFILE by default at times due to toolchain
problems with profiled code.
Can be set to "yes" or "no". Indicates
whether files destined to reside in
DESTDIR/usr/share will be
built and installed during a build. If set to "no",
then all of MKCATPAGES,
MKDOC, MKINFO,
MKMAN and MKNLS will be set
to "no" unconditionally.
Default: "yes"
Can be set to "yes" or "no". For X builds, decides if the TrueType bytecode interpreter is turned on. See freetype.org for details.
Default: "no"
Can be set to "yes" or "no". Indicates
whether an unprivileged install will occur. The user, group,
permissions and file flags will not be set on the installed items;
instead the information will be appended to a file called
METALOG in DESTDIR. The
contents of METALOG are used during the
generation of the distribution tar files to ensure that the
appropriate file ownership is stored.
Default: "no"
Can be set to "yes" or "no". Indicates
whether all install operations intended to write to
DESTDIR will compare file timestamps before
installing, and skip the install phase if the destination files
are up-to-date. This also has implications on full builds (See
below).
Default: "no"
Can be set to "yes" or "no". Indicates whether Clang should be built and installed as the host compiler.
Default: "no"
Can be set to "yes" or "no". Indicates
whether X11 is built from X11SRCDIR.
Default: "yes"
Directory to hold the host tools, once built. This directory
should be unique to a given host system and NetBSD source tree.
(However, multiple targets may share the same
TOOLDIR; the target-dependent files have unique
names). If unset, a default based on the uname(1) information
of the host platform will be created in the
.OBJDIR of src.
Default: Unset.
Indicates whether the tools specified by
TOOLDIR should be used as part of a build in
progress. Must be set to "yes" if cross-compiling.
TOOLDIR.
TOOLNAME, but refuse to build native
compilation tool components that are version-specific for
that tool.
TOOLNAME, even when building native
tool components. This is similar to the traditional NetBSD
build method, but does not verify that the compilation
tools in use are up-to-date enough in order to build the
tree successfully. This may cause build or runtime problems
when building the whole NetBSD source tree.
Default: "yes" if building all or part of a whole
NetBSD source tree (detected automatically); "no"
otherwise (to preserve traditional semantics of the
bsd.*.mk make(1) include files).
Directory containing the X11 source.
Default: "usr/xsrc"
The following variables only affect the top level
Makefile and do not affect manually building
subtrees of the NetBSD source code.
Location for the "make installworld" target to install to.
Default: "/"
Can be set to "yes" or "no". Indicates whether object directories will be created automatically (via a "make obj" pass) at the start of a build.
Default: "no"
Can be set to "yes" or "no". If set,
then addition to the effects described for
MKUPDATE=yes above, this implies the effect of
NOCLEANDIR (i.e., "make cleandir"
is avoided).
Default: "no"
If set, avoids the "make cleandir" phase of a full build. This has the effect of allowing only changed files in a source tree to recompiled. This can speed up builds when updating only a few files in the tree.
Default: Unset
If set, avoids the "make distrib-dirs" of a full
build. This skips running mtree(8) on
DESTDIR, useful on systems where building as an
unprivileged user, or where it is known that the system wide mtree
files have not changed.
Default: Unset
If set, avoids the "make includes" phase of a full
build. This has the effect of preventing make(1) from
thinking that some programs are out-of-date simply because system
include files have changed. However, this option should not be
trusted when updating the entire NetBSD source tree arbitrarily; it
is suggested to use MKUPDATE=yes in that case.
Default: Unset
If set, specifies the directory to which a release(7) layout will be written at the end of a "make release".
Default: Unset
Set to "yes" on platforms for which there is no working in-tree toolchain, or if you need/wish using native system toolchain (i.e. non-cross tools available via your shell search path).
Default: depends on target platform; on platforms with in-tree toolchain is set to "no".