xref: /src/BUILDING

BUILDING(8)                 System Manager's Manual                BUILDING(8)

NAME
     BUILDING - Procedure for building NetBSD from source code

REQUIREMENTS
     NetBSD is designed to be buildable on most POSIX-compliant host systems.
     The basic build procedure is the same whether compiling natively (on the
     same NetBSD architecture) or cross compiling (on another architecture or
     OS).

     This source tree contains the build.sh shell script which supports both
     native and cross builds of NetBSD.

     This source tree contains a special subtree, "tools", which uses the host
     system to create a build toolchain for the target architecture.  The host
     system must have at least C and C++ compilers in order to create the
     toolchain (make(1) is not required); all other tools (including make(1)
     as nbmake) are created as part of the NetBSD build process.  (See the
     Environment variables section below if you need to override or manually
     select your compilers.)

     Note: Within this document, cross-references to manual pages are to the
     NetBSD manual pages, not the host system manual pages.  The mdoc(7)
     source to the NetBSD manual pages can be found within the source tree,
     and these and can be formatted with mandoc(1) or nroff(1) if those are
     available on the host system.  The NetBSD manual pages are also available
     at https://man.netbsd.org

FILES
   Source tree layout
     BUILDING       This document (in plaintext).  Generated from
                    doc/BUILDING.mdoc.

     Makefile       The main Makefile for NetBSD; should only be run for
                    native builds with an appropriately up-to-date version of
                    NetBSD make(1).  Intended for expert use with knowledge of
                    its shortcomings, it has been superseded by the build.sh
                    shell script as the recommended means for building NetBSD.

     UPDATING       Special notes for updating from an earlier revision of
                    NetBSD.  It is important to read this file before every
                    build of an updated source tree.

     build.sh       Bourne-compatible shell script used for building the host
                    build tools and the NetBSD system from scratch.  Can be
                    used for both native and cross builds, and should be used
                    instead of make(1) as it performs additional checks to
                    prevent common issues going undetected, such as building
                    with an outdated version of make(1).

     crypto/dist/, dist/, gnu/dist/
                    Sources imported verbatim from third parties, without
                    mangling the existing build structure.  Other source trees
                    in bin through usr.sbin use the NetBSD make(1) "reachover"
                    Makefile semantics when building these programs for a
                    native host.

     distrib/, etc/
                    Sources for items used when making a full release
                    snapshot, such as files installed in DESTDIR/etc on the
                    destination system, boot media, and release notes.

     doc/BUILDING.mdoc
                    The source to this document, in mdoc(7) format.  Used to
                    generate BUILDING.

     external, sys/external
                    Sources and build infrastructure for components imported
                    (mostly) unchanged from upstream maintainers, sorted by
                    applicable license.  This is (slowly) replacing the
                    crypto/dist, dist, and gnu/dist directories.

     external/mit/xorg/
                    "Reachover" build structure for modular Xorg; the source
                    is in X11SRCDIR.

     mk.conf        Optional source tree specific mk.conf(5), used (if
                    present) instead of /etc/mk.conf unless MAKECONF is
                    defined.

                    Note: Not part of the NetBSD source repository.

     regress/, tests/
                    Regression test harness.  Can be cross-compiled, but only
                    run natively.  tests/ uses the atf(7) test framework;
                    regress/ contains older tests that have not yet been
                    migrated to atf(7).

     sys/           NetBSD kernel sources.

     tools/         "Reachover" build structure for the host build tools.
                    This has a special method of determining out-of-date
                    status.

     tools/compat/README
                    Special notes for cross-hosting a NetBSD build on non-
                    NetBSD platforms.

     Other directories including bin/ ... usr.sbin/
                    Sources to the NetBSD userland (non-kernel) programs.  If
                    any of these directories are missing, they will be skipped
                    during the build.

   Build tree layout
     The NetBSD build tree is described in hier(7) (whose mdoc(7) source is in
     share/man/man7/hier.7), and the release layout is described in release(7)
     (whose mdoc(7) source is in share/man/man7/release.7).

CONFIGURATION
   Environment variables
     Several environment variables control the behaviour of NetBSD builds.

     HOST_CC         Path name to C compiler used to create the toolchain.

                     Default: "cc".

     HOST_CFLAGS     Flags passed to the host C compiler.

                     Default: "-O".

     HOST_CPPFLAGS   Flags passed to the host C/C++ pre-processor.

                     Default: Unset.

     HOST_CXX        Path name to C++ compiler used to create the toolchain.

                     Default: Unset, but defaults to "c++" where required.

     HOST_CXXFLAGS   Flags passed to the host C++ compiler.

                     Default: Unset.

     HOST_SH         Path name to a shell available on the host system and
                     suitable for use during the build.  The NetBSD build
                     system requires a modern Bourne-like shell with POSIX-
                     compliant features, and also requires support for the
                     "local" keyword to declare local variables in shell
                     functions (which is a widely-implemented but non-
                     standardised feature).

                     Depending on the host system, a suitable shell may be
                     /bin/sh, /usr/xpg4/bin/sh, /bin/ksh (provided it is a
                     variant of ksh that supports the "local" keyword, such as
                     ksh88, but not ksh93), or /usr/local/bin/bash.

                     Most parts of the build require HOST_SH to be an absolute
                     path; however, build.sh allows it to be a simple command
                     name, which will be converted to an absolute path by
                     searching the PATH.

                     Default: "sh".

     INSTALLBOOT_UBOOT_PATHS
                     A colon-separated list of search paths used by
                     installboot(8) to find U-Boot packages.

                     Default: Unset.

     MACHINE         Machine type, e.g., "macppc".

                     Default: Unset.

     MACHINE_ARCH    Machine architecture, e.g., "powerpc".

                     Default: Unset.

     MAKE            Path name to invoke make(1) as.

                     Default: "make".

     MAKECONF        The name of the make(1) configuration file.  See "make"
                     variables and mk.conf(5).

                     Note: Only settable in the process environment.

                     Default: "/etc/mk.conf", although build.sh will set the
                     default to the full path to mk.conf if the latter is
                     present in the same directory as build.sh.

     MAKEFLAGS       Flags to invoke make(1) with.

                     Note: build.sh ignores the value of MAKEFLAGS passed in
                     the environment, but allows MAKEFLAGS to be set via the
                     -V option.

                     Default: "-X" on systems with a small ARG_MAX (Cygwin,
                     Darwin, FreeBSD); otherwise unset.

     MAKEOBJDIR      Directory to use as the .OBJDIR for the current
                     directory.  The value is subjected to variable expansion
                     by make(1).  Typical usage is to set this variable to a
                     value involving the use of `${.CURDIR:S...}' or
                     `${.CURDIR:C...}', to derive the value of .OBJDIR from
                     the value of .CURDIR.  Used only if MAKEOBJDIRPREFIX is
                     not defined.

                     Note: MAKEOBJDIR can be provided only in the environment
                     or via the -O flag of build.sh; it cannot usefully be set
                     inside a Makefile, including in mk.conf(5) or MAKECONF.

                     Default: Unset.

     MAKEOBJDIRPREFIX
                     Top level directory of the object directory tree.  The
                     value is subjected to variable expansion by make(1).
                     build.sh will create the ${MAKEOBJDIRPREFIX} directory if
                     necessary, but if make(1) is used without build.sh, then
                     rules in <bsd.obj.mk> will abort the build if the
                     ${MAKEOBJDIRPREFIX} directory does not exist.  If the
                     value is defined and valid, then
                     ${MAKEOBJDIRPREFIX}/${.CURDIR} is used as the .OBJDIR for
                     the current directory.  The current directory may be read
                     only.

                     Note: MAKEOBJDIRPREFIX can be provided only in the
                     environment or via the -M flag of build.sh; it cannot
                     usefully be set inside a Makefile, including in
                     mk.conf(5) or MAKECONF.

                     Default: Unset.

     TMPDIR          Top-level directory to store temporary directories used
                     by build.sh before paths to other directories such as
                     .OBJDIR can be determined.

                     Note: Must support execution of binaries.  I.e., without
                     mount(8)'s -o noexec option.

                     Default: "/tmp".

   "make" variables
     Variables that control the behavior of NetBSD builds are documented in
     mk.conf(5) (whose mdoc(7) source is in share/man/man5/mk.conf.5).

     Unless otherwise specified, these variables may be set in either the
     process environment or the make(1) configuration file mk.conf(5)
     specified by MAKECONF.

BUILDING
   "make" command line options
     This is not a summary of all the options available to make(1); only the
     options used most frequently with NetBSD builds are listed here.

     -j njob    Run up to njob make(1) subjobs in parallel.  Makefiles should
                use .WAIT or have explicit dependencies as necessary to
                enforce build ordering.

     -m dir     Specify the default directory for searching for system
                Makefile segments, mainly the <bsd.*.mk> files.  When building
                any full NetBSD source tree, this should be set to the
                "share/mk" directory in the source tree.  This is set
                automatically when building from the top level, or when using
                build.sh.

     -n         Show the commands that would have been executed, but do not
                actually execute them.  This will still cause recursion to
                take place.

     -V var     Show make(1)'s idea of the value of var.  Does not build any
                targets.

     var=value  Set the variable var to value, overriding any setting
                specified by the process environment, the MAKECONF
                configuration file, or the system Makefile segments.

   "make" targets
     These default targets may be built by running make(1) in any subtree of
     the NetBSD source code.  It is recommended that none of these be used
     from the top level Makefile; as a specific exception, "make obj" and
     "make cleandir" are useful in that context.

     all        Build programs, libraries, and preformatted documentation.

     clean      Remove program and library object code files.

     cleandir   Same as clean, but also remove preformatted documentation,
                dependency files generated by "make depend", and any other
                files known to be created at build time.

     depend     Create dependency files (.depend) containing more detailed
                information about the dependencies of source code on header
                files.  Allows programs to be recompiled automatically when a
                dependency changes.

     dependall  Does a "make depend" immediately followed by a "make all".
                This improves cache locality of the build since both passes
                read the source files in their entirety.

     distclean  Synonym for cleandir.

     includes   Build and install system header files.  Typically needed
                before any system libraries or programs can be built.

     install    Install programs, libraries, and documentation into DESTDIR.
                Few files will be installed to DESTDIR/dev, DESTDIR/etc,
                DESTDIR/root or DESTDIR/var in order to prevent user supplied
                configuration data from being overwritten.

     lint       Run lint(1) against the C source code, where appropriate, and
                generate system-installed lint libraries.

     obj        Create object directories to be used for built files, instead
                of building directly in the source tree.

     tags       Create ctags(1) searchable function lists usable by the ex(1)
                and vi(1) text editors.

   "make" targets for the top level
     Additional make(1) targets are usable specifically from the top source
     level to facilitate building the entire NetBSD source tree.

     build         Build the entire NetBSD system (except the kernel).  This
                   orders portions of the source tree such that prerequisites
                   will be built in the proper order.

     distribution  Do a "make build", and then install a full distribution
                   (which does not include a kernel) into DESTDIR, including
                   files in DESTDIR/dev, DESTDIR/etc, DESTDIR/root and
                   DESTDIR/var.

     buildworld    As per "make distribution", except that it ensures that
                   DESTDIR is not the root directory.

     installworld  Install the distribution from DESTDIR to INSTALLWORLDDIR,
                   which defaults to the root directory.  Ensures that
                   INSTALLWORLDDIR is not the root directory if cross
                   compiling.

                   The INSTALLSETS environment variable may be set to a space-
                   separated list of distribution sets to be installed.  By
                   default, all sets except "etc" and "xetc" are installed, so
                   most files in INSTALLWORLDDIR/etc will not be installed or
                   modified.

                   Note: Before performing this operation with
                   INSTALLWORLDDIR=/, it is highly recommended that you
                   upgrade your kernel and reboot.  After performing this
                   operation, it is recommended that you use etcupdate(8) to
                   update files in INSTALLWORLDDIR/etc, and postinstall(8) to
                   check for or fix inconsistencies.

     sets          Create distribution sets from DESTDIR into
                   RELEASEDIR/RELEASEMACHINEDIR/binary/sets.  Should be run
                   after "make distribution", as "make build" alone does not
                   install all of the required files.

     sourcesets    Create source sets of the source tree into
                   RELEASEDIR/source/sets.

     syspkgs       Create syspkgs from DESTDIR into
                   RELEASEDIR/RELEASEMACHINEDIR/binary/syspkgs.  Should be run
                   after "make distribution", as "make build" alone does not
                   install all of the required files.

     release       Do a "make distribution", build kernels, distribution
                   media, and install sets (this as per "make sets"), and then
                   package the system into a standard release layout as
                   described by release(7).  This requires that RELEASEDIR be
                   set (see above).

     iso-image     Create a NetBSD installation CD-ROM image in the
                   RELEASEDIR/images directory.  The CD-ROM file system will
                   have a layout as described in release(7).

                   For most machine types, the CD-ROM will be bootable, and
                   will automatically run the sysinst(8) menu-based
                   installation program, which can be used to install or
                   upgrade a NetBSD system.  Bootable CD-ROMs also contain
                   tools that may be useful in repairing a damaged NetBSD
                   installation.

                   Before "make iso-image" is attempted, RELEASEDIR must be
                   populated by "make release" or equivalent.

                   Note: Other, smaller, CD-ROM images may be created in the
                   RELEASEDIR/RELEASEMACHINEDIR/installation/cdrom directory
                   by "make release".  These smaller images usually contain
                   the same tools as the larger images in RELEASEDIR/images,
                   but do not contain additional content such as the
                   distribution sets.

                   Note: The mac68k port still uses an older method of
                   creating CD-ROM images.  This requires the mkisofs(1)
                   utility, which is not part of NetBSD, but which can be
                   installed from pkgsrc/sysutils/cdrtools.

     iso-image-source
                   Create a NetBSD installation CD-ROM image in the
                   RELEASEDIR/images directory.  The CD-ROM file system will
                   have a layout as described in release(7).  It will have top
                   level directories for the machine type and source.

                   For most machine types, the CD-ROM will be bootable, and
                   will automatically run the sysinst(8) menu-based
                   installation program, which can be used to install or
                   upgrade a NetBSD system.  Bootable CD-ROMs also contain
                   tools that may be useful in repairing a damaged NetBSD
                   installation.

                   Before "make iso-image-source" is attempted, RELEASEDIR
                   must be populated by "make sourcesets release" or
                   equivalent.

                   Note: Other, smaller, CD-ROM images may be created in the
                   RELEASEDIR/RELEASEMACHINEDIR/installation/cdrom directory
                   by "make release".  These smaller images usually contain
                   the same tools as the larger images in RELEASEDIR/images,
                   but do not contain additional content such as the
                   distribution sets.

                   Note: The mac68k port still uses an older method of
                   creating CD-ROM images.  This requires the mkisofs(1)
                   utility, which is not part of NetBSD, but which can be
                   installed from pkgsrc/sysutils/cdrtools.

     install-image
                   Create a bootable NetBSD installation disk image in the
                   RELEASEDIR/images directory.  The installation disk image
                   is suitable for copying to bootable USB flash memory
                   sticks, etc., for machines which are able to boot from such
                   devices.  The file system in the bootable disk image will
                   have a layout as described in release(7).

                   The installation image is bootable, and will automatically
                   run the sysinst(8) menu-based installation program, which
                   can be used to install or upgrade a NetBSD system.  The
                   image also contains tools that may be useful in repairing a
                   damaged NetBSD installation.

                   Before "make install-image" is attempted, RELEASEDIR must
                   be populated by "make release" or equivalent.  The build
                   must have been performed with MKUNPRIVED=yes because "make
                   install-image" relies on information in DESTDIR/METALOG.

     live-image    Create NetBSD live images in the RELEASEDIR/images
                   directory.  The live image contains all necessary files to
                   boot NetBSD up to multi-user mode, including all files
                   which should be extracted during installation, NetBSD
                   disklabel, bootloaders, etc.

                   The live image is suitable for use as a disk image in
                   virtual machine environments such as QEMU, and also useful
                   to boot NetBSD from a USB flash memory stick on a real
                   machine, without the need for installation.

                   Before "make live-image" is attempted, RELEASEDIR must be
                   populated by "make release" or equivalent.  The build must
                   have been performed with MKUNPRIVED=yes because "make
                   install-image" relies on information in DESTDIR/METALOG.

     regression-tests
                   Can only be run after building the regression tests in the
                   directory "regress".  Runs those compiled regression tests
                   on the local host.

                   Note: Most tests are now managed instead using atf(7); this
                   target should probably run those as well but currently does
                   not.

   The "build.sh" script
     This script file is a shell script designed to build the entire NetBSD
     system on any host with a suitable modern shell and some common
     utilities.  The required shell features are described under the HOST_SH
     variable.

     If a host system's default shell does support the required features, then
     we suggest that you explicitly specify a suitable shell using a command
     like

           /path/to/suitable/shell build.sh [options]

     The above command will usually enable build.sh to automatically set
     HOST_SH=/path/to/suitable/shell, but if that fails, then the following
     set of commands may be used instead:

           HOST_SH=/path/to/suitable/shell
           export HOST_SH
           ${HOST_SH} build.sh [options]

     If build.sh detects that it is being executed under an unsuitable shell,
     it attempts to exec a suitable shell instead, or shows an error message.
     If HOST_SH is not set explicitly, then build.sh sets a default using
     heuristics dependent on the host platform, or from the shell under which
     build.sh is executed (if that can be determined), or using the first copy
     of sh found in PATH.

     All cross-compile builds, and most native builds, of the entire system
     should make use of build.sh rather than just running "make".  This way,
     the make(1) program will be bootstrapped properly, in case the host
     system has an older or incompatible "make" program.

     When compiling the entire system via build.sh, many make(1) variables are
     set for you in order to help encapsulate the build process.  In the list
     of options below, variables that are automatically set by build.sh are
     noted where applicable.

     The following operations are supported by build.sh:

     build         Build the system as per "make build".  Before the main part
                   of the build commences, this command runs the obj operation
                   (unless the -o option is given), "make cleandir" (unless
                   the -u option is given), and the tools operation.

     distribution  Build a full distribution as per "make distribution".  This
                   command first runs the build operation.

     release       Build a full release as per "make release".  This command
                   first runs the distribution operation.

     help          Show a help message, and exit.

     makewrapper   Create the nbmake-MACHINE wrapper.  This operation is
                   automatically performed for any of the other operations.

     cleandir      Perform "make cleandir".

     obj           Perform "make obj".

     tools         Build and install the host tools from src/tools.  This
                   command will first run "make obj" and "make cleandir" in
                   the tools subdirectory unless the -o or -u options
                   (respectively) are given.

     install=idir  Install the contents of DESTDIR to idir, using "make
                   installworld".

                   Note: Files that are part of the "etc" or "xetc" sets will
                   not be installed, unless overridden by the INSTALLSETS
                   environment variable.

     kernel=kconf  Build a new kernel.  The kconf argument is the name of a
                   configuration file suitable for use by config(1).  If kconf
                   does not contain any `/' characters, the configuration file
                   is expected to be found in the KERNCONFDIR directory, which
                   is typically sys/arch/MACHINE/conf.  The new kernel will be
                   built in a subdirectory of KERNOBJDIR, which is typically
                   sys/arch/MACHINE/compile or an associated object directory.

                   This command does not imply the tools command; run the
                   tools command first unless it is certain that the tools
                   already exist and are up to date.

                   This command will run "make cleandir" on the kernel in
                   question first unless the -u option is given.

     kernel.gdb=kconf
                   Build a new kernel with debug information.  Similar to the
                   above kernel=kconf operation, but creates a netbsd.gdb file
                   alongside of the kernel netbsd, which contains a full
                   symbol table and can be used for debugging (for example
                   with a cross-gdb built by MKCROSSGDB).

     kernels       This command will build all kernels defined in port
                   specific release build procedure.

                   This command internally calls the kernel=kconf operation
                   for each found kernel configuration file.

     modules       This command will build kernel modules and install them
                   into DESTDIR.

     releasekernel=kconf
                   Install a gzip(1)ed copy of the kernel previously built by
                   kernel=kconf into
                   RELEASEDIR/RELEASEMACHINEDIR/binary/kernel, usually as
                   netbsd-kconf.gz, although the "netbsd" prefix is determined
                   from the "config" directives in kconf.

     sets          Perform "make sets".

     sourcesets    Perform "make sourcesets".

     syspkgs       Perform "make syspkgs".

     iso-image     Perform "make iso-image".

     iso-image-source
                   Perform "make iso-image-source".

     install-image
                   Perform "make install-image".

     live-image    Perform "make live-image".

     list-arch     Show a list of valid MACHINE and MACHINE_ARCH settings, the
                   default MACHINE_ARCH for each MACHINE, and aliases for
                   MACHINE/MACHINE_ARCH pairs, and then exits.  The -m or -a
                   options (or both) may be used to specify glob patterns that
                   will be used to narrow the list of results; for example,
                   "build.sh -m 'evb*' -a '*arm*' list-arch" will list all
                   known MACHINE/MACHINE_ARCH values in which either MACHINE
                   or ALIAS matches the pattern `evb*', and MACHINE_ARCH
                   matches the pattern `*arm*'.

     The following command line options alter the behaviour of the build.sh
     operations described above:

     -a arch   Set the value of MACHINE_ARCH to arch.  See the -m option for
               more information.

     -B buildid
               Set the value of BUILDID to buildid.  This will also append the
               build identifier to the name of the "make" wrapper script so
               that the resulting name is of the form
               "nbmake-MACHINE-BUILDID".

     -C cdextras
               Append cdextras to the CDEXTRA variable, which is a space-
               separated list of files or directories that will be added to
               the CD-ROM image that may be create by the "iso-image" or
               "iso-image-source" operations.  Files will be added to the root
               of the CD-ROM image, whereas directories will be copied
               recursively.  If relative paths are specified, they will be
               converted to absolute paths before being used.  Multiple paths
               may be specified via multiple -C options, or via a single
               option whose argument contains multiple space-separated paths.

     -c compiler
               Select the compiler for the toolchain to build NetBSD and for
               inclusion in the NetBSD distribution.  Supported choices:

                     clang

                     gcc [default]

               The compiler used to build the toolchain can be different; see
               HOST_CC and HOST_CXX.

     -D dest   Set the value of DESTDIR to dest.  If a relative path is
               specified, it will be converted to an absolute path before
               being used.

     -E        Set `expert' mode.  This overrides various sanity checks, and
               allows: DESTDIR does not have to be set to a non-root path for
               builds, and MKUNPRIVED=yes does not have to be set when
               building as a non-root user.

               Note: It is highly recommended that you know what you are doing
               when you use this option.

     -h        Show a help message, and exit.

     -j njob   Run up to njob make(1) subjobs in parallel; passed through to
               make(1).  If you see failures for reasons other than running
               out of memory while using build.sh with -j, please save
               complete build logs so the failures can be analyzed.

               To achieve the fastest builds, -j values between (1 + the
               number of CPUs) and (2 * the number of CPUs) are recommended.
               Use lower values on machines with limited memory or I/O
               bandwidth.

     -M obj    Set MAKEOBJDIRPREFIX to obj.  Unsets MAKEOBJDIR.  See "-O obj"
               for more information.

               For instance, if the source directory is /usr/src, a setting of
               "-M /usr/obj" will place build-time files under
               /usr/obj/usr/src/bin, /usr/obj/usr/src/lib,
               /usr/obj/usr/src/usr.bin, and so forth.

               If a relative path is specified, it will be converted to an
               absolute path before being used.  build.sh imposes the
               restriction that the argument to the -M option must not begin
               with a "$" (dollar sign) character; otherwise it would be too
               difficult to determine whether the value is an absolute or a
               relative path.  If the directory does not already exist,
               build.sh will create it.

     -m mach   Set the value of MACHINE to mach, unless the mach argument is
               an alias that refers to a MACHINE/MACHINE_ARCH pair, in which
               case both MACHINE and MACHINE_ARCH are set from the alias.
               Such aliases are interpreted entirely by build.sh; they are not
               used by any other part of the build system.  The MACHINE_ARCH
               setting implied by mach will override any value of MACHINE_ARCH
               in the process environment, but will not override a value set
               by the -a option.  All cross builds require -m, but if unset on
               a NetBSD host, the host's value of MACHINE will be detected and
               used automatically.

               See the list-arch operation for a way to get a list of valid
               MACHINE and MACHINE_ARCH settings.

     -N noiselevel
               Set the "noisyness" level of the build, by setting MAKEVERBOSE
               to noiselevel.

     -n        Show the commands that would be executed by build.sh, but do
               not make any changes.  This is similar in concept to "make -n".

     -O obj    Create an appropriate transform macro for MAKEOBJDIR that will
               place the built object files under obj.  Unsets
               MAKEOBJDIRPREFIX.

               For instance, a setting of "-O /usr/obj" will place build-time
               files under /usr/obj/bin, /usr/obj/lib, /usr/obj/usr.bin, and
               so forth.

               If a relative path is specified, it will be converted to an
               absolute path before being used.  build.sh imposes the
               restriction that the argument to the -O option must not contain
               a "$" (dollar sign) character.  If the directory does not
               already exist, build.sh will create it.

               In normal use, exactly one of the -M or -O options should be
               specified.  If neither -M nor -O is specified, then a default
               object directory will be chosen according to rules in
               <bsd.obj.mk>.  Relying on this default is not recommended
               because it is determined by complex rules that are influenced
               by the values of several variables and by the location of the
               source directory.

               Note: Placing the obj directory location outside of the default
               source tree hierarchy makes it easier to manually clear out old
               files in the event the "make cleandir" operation is unable to
               do so.  (See CAVEATS below.)

               Note: The use of one of -M or -O is the only means of building
               multiple machine architecture userlands from the same source
               tree without cleaning between builds (in which case, one would
               specify distinct obj locations for each).

     -o        Set the value of MKOBJDIRS to "no".  Otherwise, it will be
               automatically set to "yes".  This default is opposite to the
               behaviour when not using build.sh.

     -P        Set the value of MKREPRO and MKREPRO_TIMESTAMP to the latest
               source CVS timestamp for reproducible builds.

     -R rel    Set the value of RELEASEDIR to rel.  If a relative path is
               specified, it will be converted to an absolute path before
               being used.

     -r        Remove the contents of DESTDIR and TOOLDIR before building
               (provides a clean starting point).  This will skip deleting
               DESTDIR if building on a native system to the root directory.

     -S seed   Change the value of BUILDSEED to seed.  This should rarely be
               necessary.

     -T tools  Set the value of TOOLDIR to tools.  If a relative path is
               specified, it will be converted to an absolute path before
               being used.  If set, the bootstrap "make" will only be rebuilt
               if the source files for make(1) have changed.

     -U        Set MKUNPRIVED=yes.

     -u        Set MKUPDATE=yes.

     -V var=[value]
               Set the environment variable var to an optional value.  This is
               propagated to the nbmake wrapper.

     -w wrapper
               Create the nbmake wrapper script (see below) in a custom
               location, specified by wrapper.  This allows, for instance, to
               place the wrapper in PATH automatically.

               Note: wrapper is the full name of the file, not just a
               directory name.  If a relative path is specified, it will be
               converted to an absolute path before being used.

     -X x11src
               Set the value of X11SRCDIR to x11src.  If a relative path is
               specified, it will be converted to an absolute path before
               being used.

     -x        Set MKX11=yes.

     -Z var    Unset ("zap") the environment variable var.  This is propagated
               to the nbmake wrapper.

     -?        Show a help message, and exit.

   The "nbmake-MACHINE" wrapper script
     If using the build.sh script to build NetBSD, a nbmake-MACHINE script
     will be created in TOOLDIR/bin upon the first build to assist in building
     subtrees on a cross-compile host.

     nbmake-MACHINE can be invoked in lieu of make(1), and will instead call
     the up-to-date version of "nbmake" installed into TOOLDIR/bin with
     several key variables pre-set, including MACHINE, MACHINE_ARCH, and
     TOOLDIR.  nbmake-MACHINE will also set variables specified with -V, and
     unset variables specified with -Z.

     This script can be symlinked into a directory listed in PATH, or called
     with an absolute path.

EXAMPLES
     1.   % ./build.sh [OPTIONS] tools kernel=GENERIC

          Build a new toolchain, and use the new toolchain to configure and
          build a new GENERIC kernel.

     2.   % ./build.sh [OPTIONS] -U distribution

          Using unprivileged mode, build a complete distribution to a DESTDIR
          directory that build.sh selects (and will show).

     3.   # ./build.sh [OPTIONS] -U install=/

          As root, install to / the distribution that was built by example 2.
          Even though this is run as root, -U is required so that the
          permissions stored in DESTDIR/METALOG are correctly applied to the
          files as they're copied to /.

     4.   % ./build.sh [OPTIONS] -U -u release

          Using unprivileged mode, build a complete release to DESTDIR and
          RELEASEDIR directories that build.sh selects (and will show).
          MKUPDATE=yes (-u) is set to prevent the "make cleandir", so that if
          this is run after example 2, it doesn't need to redo that portion of
          the release build.

SEE ALSO
     config(1), ctags(1), ex(1), gzip(1), lint(1), make(1), mandoc(1),
     mkisofs(1), nroff(1), vi(1), mk.conf(5), atf(7), hier(7), mdoc(7),
     release(7), etcupdate(8), installboot(8), mount(8), postinstall(8),
     sysinst(8), pkgsrc/sysutils/cdrtools

     Note: The NetBSD manual pages are also available at
     https://man.netbsd.org

HISTORY
     The build.sh based build scheme was introduced for NetBSD 1.6 as
     USE_NEW_TOOLCHAIN, and re-worked to TOOLCHAIN_MISSING after that.

CAVEATS
     After significant updates to third-party components in the source tree,
     the "make cleandir" operation may be insufficient to clean out old files
     in object directories.  Instead, one may have to manually remove the
     files.  Consult the UPDATING file for notices concerning this.

NetBSD                           July 18, 2023                          NetBSD