xref: /freebsd/share/man/man7/build.7 (revision 70ccb89db2a28998a85b60023e7b3211db540cab)
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28.Dd February 3, 2025
29.Dt BUILD 7
30.Os
31.Sh NAME
32.Nm build
33.Nd general instructions on how to build the
34.Fx
35system
36.Sh DESCRIPTION
37The sources for the
38.Fx
39system and its applications are contained in three different directories,
40normally
41.Pa /usr/src ,
42.Pa /usr/doc ,
43and
44.Pa /usr/ports .
45These directories may be initially empty or non-existent until updated with
46Git
47.Po installed from packages with
48.Xr pkg 7
49or from
50.Xr ports 7 Pc .
51Directory
52.Pa /usr/src
53contains the
54.Dq "base system"
55sources, which is loosely defined as the things required to rebuild
56the system to a useful state.
57Directory
58.Pa /usr/doc
59contains the source for the system documentation, excluding the manual
60pages.
61Directory
62.Pa /usr/ports
63contains a tree that provides a consistent interface for building and
64installing third party applications.
65For more information about the ports build process, see
66.Xr ports 7 .
67.Pp
68The
69.Xr make 1
70command is used in each of these directories to build and install the
71things in that directory.
72Issuing the
73.Xr make 1
74command in any directory issues the
75.Xr make 1
76command recursively in all subdirectories.
77With no target specified, the items in the directories are built
78and no further action is taken.
79.Pp
80A source tree is allowed to be read-only.
81As described in
82.Xr make 1 ,
83objects are usually built in a separate object directory hierarchy
84specified by the environment variable
85.Va MAKEOBJDIRPREFIX ,
86or under
87.Pa /usr/obj
88if variable
89.Va MAKEOBJDIRPREFIX
90is not set.
91The canonical object directory is described in the documentation for the
92.Cm buildworld
93target below.
94.Pp
95The build may be controlled by defining
96.Xr make 1
97variables described in the
98.Sx ENVIRONMENT
99section below, and by the variables documented in
100.Xr make.conf 5 .
101.Pp
102The default components included in the build are specified in the file
103.Pa /etc/src.conf
104in the source tree.
105To override the default file, include the SRCCONF option in the make steps,
106pointing to a custom src.conf file.
107For more information see
108.Xr src.conf 5 .
109.Pp
110The following list provides the names and actions for the targets
111supported by the build system:
112.Bl -tag -width ".Cm cleandepend"
113.It Cm analyze
114Run Clang static analyzer against all objects and present output on stdout.
115.It Cm check
116Run tests for a given subdirectory.
117The default directory used is
118.Pa ${.OBJDIR} ,
119but the check directory can be changed with
120.Pa ${CHECKDIR} .
121.It Cm checkworld
122Run the
123.Fx
124test suite on installed world.
125.It Cm clean
126Remove any files created during the build process.
127.It Cm cleandepend
128Remove the
129.Pa ${.OBJDIR}/${DEPENDFILE}*
130files generated by prior
131.Dq Li "make"
132and
133.Dq Li "make depend"
134steps.
135.It Cm cleandir
136Remove the canonical object directory if it exists, or perform
137actions equivalent to
138.Dq Li "make clean cleandepend"
139if it does not.
140This target will also remove an
141.Pa obj
142link in
143.Pa ${.CURDIR}
144if that exists.
145.Pp
146It is advisable to run
147.Dq Li "make cleandir"
148twice: the first invocation will remove the canonical object directory
149and the second one will clean up
150.Pa ${.CURDIR} .
151.It Cm depend
152Generate a list of build dependencies in file
153.Pa ${.OBJDIR}/${DEPENDFILE} .
154Per-object dependencies are generated at build time and stored in
155.Pa ${.OBJDIR}/${DEPENDFILE}.${OBJ} .
156.It Cm install
157Install the results of the build to the appropriate location in the
158installation directory hierarchy specified in variable
159.Va DESTDIR .
160.It Cm obj
161Create the canonical object directory associated with the current
162directory.
163.It Cm objlink
164Create a symbolic link to the canonical object directory in
165.Pa ${.CURDIR} .
166.It Cm tags
167Generate a tags file using the program specified in the
168.Xr make 1
169variable
170.Va CTAGS .
171The build system supports
172.Xr ctags 1
173and
174.Nm "GNU Global" .
175.El
176.Pp
177The other supported targets under directory
178.Pa /usr/src
179are:
180.Bl -tag -width ".Cm distributeworld"
181.It Cm buildenv
182Spawn an interactive shell with environment variables set up for
183building the system or individual components.
184For cross-building the target architecture needs to be specified with
185.Xr make 1
186variables
187.Va TARGET_ARCH
188and
189.Va TARGET .
190.Pp
191This target is only useful after a complete toolchain (including
192the compiler, linker, assembler, headers and libraries) has been
193built; see the
194.Cm toolchain
195target below.
196.It Cm buildworld
197Build everything but the kernel, configure files in
198.Pa etc ,
199and
200.Pa release .
201The object directory can be changed from the default
202.Pa /usr/obj
203by setting the
204.Pa MAKEOBJDIRPREFIX
205.Xr make 1
206variable.
207The actual build location prefix used
208depends on the
209.Va WITH_UNIFIED_OBJDIR
210option from
211.Xr src.conf 5 .
212If enabled it is
213.Pa ${MAKEOBJDIRPREFIX}${.CURDIR}/${TARGET}.${TARGET_ARCH}
214for all builds.
215If disabled it is
216.Pa ${MAKEOBJDIRPREFIX}${.CURDIR}
217for native builds, and
218.Pa ${MAKEOBJDIRPREFIX}/${TARGET}.${TARGET_ARCH}${.CURDIR}
219for cross builds and native builds with variable
220.Va CROSS_BUILD_TESTING
221set.
222.It Cm cleankernel
223Attempts to clean up targets built by a preceding
224.Cm buildkernel ,
225or similar step, built from the same source directory and
226.Va KERNCONF .
227.It Cm cleanworld
228Attempt to clean up targets built by a preceding
229.Cm buildworld ,
230or similar step, built from this source directory.
231.It Cm cleanuniverse
232When
233.Va WITH_UNIFIED_OBJDIR
234is enabled, attempt to clean up targets built by a preceding
235.Cm buildworld ,
236.Cm universe ,
237or similar step, for any architecture built from this source directory.
238.It Cm distributeworld
239Distribute everything compiled by a preceding
240.Cm buildworld
241step.
242Files are placed in the directory hierarchy specified by
243.Xr make 1
244variable
245.Va DISTDIR .
246This target is used while building a release; see
247.Xr release 7 .
248.It Cm native-xtools
249This target builds a cross-toolchain for the given
250.Sy TARGET
251and
252.Sy TARGET_ARCH ,
253as well as a select list of static userland tools for the host system.
254This is intended to be used in a jail where QEMU is used to improve
255performance by avoiding emulating binaries that do not need to be emulated.
256.Sy TARGET
257and
258.Sy TARGET_ARCH
259should be defined.
260.It Cm native-xtools-install
261Installs the results to
262.Pa ${DESTDIR}/${NXTP}
263where
264.Va NXTP
265defaults to
266.Pa nxb-bin .
267.Sy TARGET
268and
269.Sy TARGET_ARCH
270must be defined.
271.It Cm packageworld
272Archive the results of
273.Cm distributeworld ,
274placing the results in
275.Va DISTDIR .
276This target is used while building a release; see
277.Xr release 7 .
278.It Cm installworld
279Install everything built by a preceding
280.Cm buildworld
281step into the directory hierarchy pointed to by
282.Xr make 1
283variable
284.Va DESTDIR .
285.Pp
286If installing onto an NFS file system and running
287.Xr make 1
288with the
289.Fl j
290option, make sure that
291.Xr rpc.lockd 8
292is running on both client and server.
293See
294.Xr rc.conf 5
295on how to make it start at boot time.
296.It Cm toolchain
297Create the build toolchain needed to build the rest of the system.
298For cross-architecture builds, this step creates a cross-toolchain.
299.It Cm universe
300For each architecture,
301execute a
302.Cm buildworld
303followed by a
304.Cm buildkernel
305for all kernels for that architecture,
306including
307.Pa LINT .
308This command takes a long time.
309.It Cm kernels
310Like
311.Cm universe
312with
313.Va WITHOUT_WORLDS
314defined so only the kernels for each architecture are built.
315.It Cm worlds
316Like
317.Cm universe
318with
319.Va WITHOUT_KERNELS
320defined so only the worlds for each architecture are built.
321.It Cm targets
322Print a list of supported
323.Va TARGET
324/
325.Va TARGET_ARCH
326pairs for world and kernel targets.
327.It Cm tinderbox
328Execute the same targets as
329.Cm universe .
330In addition print a summary of all failed targets at the end and
331exit with an error if there were any.
332.It Cm toolchains
333Create a build toolchain for each architecture supported by the build system.
334.It Cm xdev
335Builds and installs a cross-toolchain and sysroot for the given
336.Sy TARGET
337and
338.Sy TARGET_ARCH .
339The sysroot contains target library and headers.
340The target is an alias for
341.Cm xdev-build
342and
343.Cm xdev-install .
344The location of the files installed can be controlled with
345.Va DESTDIR .
346The target location in
347.Va DESTDIR
348is
349.Pa ${DESTDIR}/${XDTP}
350where
351.Va XDTP
352defaults to
353.Pa /usr/${XDDIR}
354and
355.Va XDDIR
356defaults to
357.Pa ${TARGET_ARCH}-freebsd .
358.It Cm xdev-build
359Builds for the
360.Cm xdev
361target.
362.It Cm xdev-install
363Installs the files for the
364.Cm xdev
365target.
366.It Cm xdev-links
367Installs autoconf-style symlinks to
368.Pa ${DESTDIR}/usr/bin
369pointing into the xdev toolchain in
370.Pa ${DESTDIR}/${XDTP} .
371.El
372.Pp
373Kernel specific build targets in
374.Pa /usr/src
375are:
376.Bl -tag -width ".Cm distributekernel"
377.It Cm buildkernel
378Rebuild the kernel and the kernel modules.
379The object directory can be changed from the default
380.Pa /usr/obj
381by setting the
382.Pa MAKEOBJDIRPREFIX
383.Xr make 1
384variable.
385.It Cm installkernel
386Install the kernel and the kernel modules to directory
387.Pa ${DESTDIR}/boot/kernel ,
388renaming any pre-existing directory with this name to
389.Pa kernel.old
390if it contained the currently running kernel.
391The target directory under
392.Pa ${DESTDIR}
393may be modified using the
394.Va INSTKERNNAME
395and
396.Va KODIR
397.Xr make 1
398variables.
399.It Cm distributekernel
400Install the kernel to the directory
401.Pa ${DISTDIR}/kernel/boot/kernel .
402This target is used while building a release; see
403.Xr release 7 .
404.It Cm packages
405Create a
406.Xr pkg 7
407repository containing packages that can be used to create or upgrade an
408installation of the base system.
409The output repository is placed in the object directory, under
410.Pa repo/${PKG_ABI}
411where
412.Va PKG_ABI
413is the
414.Xr pkg 7
415ABI for the build target, for example,
416.Pa /usr/obj/${SRCDIR}/repo/FreeBSD:15:amd64 .
417.It Cm packagekernel
418Archive the results of
419.Cm distributekernel ,
420placing the results in
421.Va DISTDIR .
422This target is used while building a release; see
423.Xr release 7 .
424.It Cm kernel
425Equivalent to
426.Cm buildkernel
427followed by
428.Cm installkernel
429.It Cm kernel-toolchain
430Rebuild the tools needed for kernel compilation.
431Use this if you did not do a
432.Cm buildworld
433first.
434.It Cm reinstallkernel
435Reinstall the kernel and the kernel modules, overwriting the contents
436of the target directory.
437As with the
438.Cm installkernel
439target, the target directory can be specified using the
440.Xr make 1
441variable
442.Va INSTKERNNAME .
443.El
444.Pp
445Convenience targets for cleaning up the install destination directory
446denoted by variable
447.Va DESTDIR
448include:
449.Bl -tag -width ".Cm delete-old-libs"
450.It Cm check-old
451Print a list of old files and directories in the system.
452.It Cm check-old-libs
453Print a list of obsolete base system libraries.
454.It Cm delete-old
455Delete obsolete base system files and directories interactively.
456When
457.Li -DBATCH_DELETE_OLD_FILES
458is specified at the command line, the delete operation will be
459non-interactive.
460The variables
461.Va DESTDIR ,
462.Va TARGET_ARCH
463and
464.Va TARGET
465should be set as with
466.Dq Li "make installworld" .
467.It Cm delete-old-libs
468Delete obsolete base system libraries interactively.
469This target should only be used if no third party software uses these
470libraries.
471When
472.Li -DBATCH_DELETE_OLD_FILES
473is specified at the command line, the delete operation will be
474non-interactive.
475The variables
476.Va DESTDIR ,
477.Va TARGET_ARCH
478and
479.Va TARGET
480should be set as with
481.Dq Li "make installworld" .
482.El
483.Sh ENVIRONMENT
484Variables that influence all builds include:
485.Bl -tag -width ".Va MAKEOBJDIRPREFIX"
486.It Va DEBUG_FLAGS
487Defines a set of debugging flags that will be used to build all userland
488binaries under
489.Pa /usr/src .
490When
491.Va DEBUG_FLAGS
492is defined, the
493.Cm install
494and
495.Cm installworld
496targets install binaries from the current
497.Va MAKEOBJDIRPREFIX
498without stripping,
499so that debugging information is retained in the installed binaries.
500.It Va DESTDIR
501The directory hierarchy prefix where built objects will be installed.
502If not set,
503.Va DESTDIR
504defaults to the empty string.
505If set,
506.Va DESTDIR
507must specify an absolute path.
508.It Va MAKEOBJDIRPREFIX
509Defines the prefix for directory names in the tree of built objects.
510Defaults to
511.Pa /usr/obj
512if not defined.
513This variable should only be set in the environment or
514.Pa /etc/src-env.conf
515and not via
516.Pa /etc/make.conf
517or
518.Pa /etc/src.conf
519or the command line.
520.Va MAKEOBJDIRPREFIX
521must specify an absolute path.
522.It Va WITHOUT_WERROR
523If defined, compiler warnings will not cause the build to halt,
524even if the makefile says otherwise.
525.It Va WITH_CTF
526If defined, the build process will run the DTrace CTF conversion
527tools on built objects.
528.El
529.Pp
530Additionally, builds in
531.Pa /usr/src
532are influenced by the following
533.Xr make 1
534variables:
535.Bl -tag -width ".Va LOCAL_MODULES_DIR"
536.It Va CROSS_TOOLCHAIN
537Requests use of an external toolchain to build either the world or kernel.
538This value of this variable can either be the full path to a file,
539or the base name of a file in
540.Pa ${LOCALBASE}/share/toolchains .
541The file should be a make file which sets variables to request an external
542toolchain such as
543.Va XCC .
544.Pp
545External toolchains are available in ports for both LLVM and GCC/binutils.
546For external toolchains available in ports,
547.Va CROSS_TOOLCHAIN
548should be set to the name of the package.
549LLVM toolchain packages use the name llvm<major version>.
550GCC toolchains provide separate packages for each architecture and use the
551name ${MACHINE_ARCH}-gcc<major version>.
552.It Va KERNCONF
553Overrides which kernel to build and install for the various kernel
554make targets.
555It defaults to
556.Cm GENERIC .
557.It Va KERNCONFDIR
558Overrides the directory in which
559.Va KERNCONF
560and any files included by
561.Va KERNCONF
562should be found.
563Defaults to
564.Pa sys/${ARCH}/conf .
565.It Va KERNFAST
566If set, the build target
567.Cm buildkernel
568defaults to setting
569.Va NO_KERNELCLEAN ,
570.Va NO_KERNELCONFIG ,
571and
572.Va NO_KERNELOBJ .
573When set to a value other than
574.Cm 1
575then
576.Va KERNCONF
577is set to the value of
578.Va KERNFAST .
579.It Va LOCAL_DIRS
580If set, this variable supplies a list of additional directories relative to
581the root of the source tree to build as part of the
582.Cm everything
583target.
584The directories are built in parallel with each other,
585and with the base system directories.
586Insert a
587.Va .WAIT
588directive at the beginning of the
589.Va LOCAL_DIRS
590list to ensure all base system directories are built first.
591.Va .WAIT
592may also be used as needed elsewhere within the list.
593.It Va LOCAL_ITOOLS
594If set, this variable supplies a list of additional tools that are used by the
595.Cm installworld
596and
597.Cm distributeworld
598targets.
599.It Va LOCAL_LIB_DIRS
600If set, this variable supplies a list of additional directories relative to
601the root of the source tree to build as part of the
602.Cm libraries
603target.
604The directories are built in parallel with each other,
605and with the base system libraries.
606Insert a
607.Va .WAIT
608directive at the beginning of the
609.Va LOCAL_DIRS
610list to ensure all base system libraries are built first.
611.Va .WAIT
612may also be used as needed elsewhere within the list.
613.It Va LOCAL_MTREE
614If set, this variable supplies a list of additional mtrees relative to the
615root of the source tree to use as part of the
616.Cm hierarchy
617target.
618.It Va LOCAL_LEGACY_DIRS
619If set, this variable supplies a list of additional directories relative to
620the root of the source tree to build as part of the
621.Cm legacy
622target.
623.It Va LOCAL_BSTOOL_DIRS
624If set, this variable supplies a list of additional directories relative to
625the root of the source tree to build as part of the
626.Cm bootstrap-tools
627target.
628.It Va LOCAL_TOOL_DIRS
629If set, this variable supplies a list of additional directories relative to
630the root of the source tree to build as part of the
631.Cm build-tools
632target.
633.It Va LOCAL_XTOOL_DIRS
634If set, this variable supplies a list of additional directories relative to
635the root of the source tree to build as part of the
636.Cm cross-tools
637target.
638.It Va PORTS_MODULES
639A list of ports with kernel modules that should be built and installed
640as part of the
641.Cm buildkernel
642and
643.Cm installkernel
644process.
645.Bd -literal -offset indent
646make PORTS_MODULES=emulators/virtualbox-ose-kmod kernel
647.Ed
648.It Va LOCAL_MODULES
649A list of external kernel modules that should be built and installed
650as part of the
651.Cm buildkernel
652and
653.Cm installkernel
654process.
655Defaults to the list of sub-directories of
656.Va LOCAL_MODULES_DIR .
657.It Va LOCAL_MODULES_DIR
658The directory in which to search for the kernel modules specified by
659.Va LOCAL_MODULES .
660Each kernel module should consist of a directory containing a makefile.
661Defaults to
662.Pa ${LOCALBASE}/sys/modules .
663.It Va SRCCONF
664Specify a file to override the default
665.Pa /etc/src.conf .
666The src.conf file controls the components to build.
667See
668.Xr src.conf 5
669.It Va STRIPBIN
670Command to use at install time when stripping binaries.
671Be sure to add any additional tools required to run
672.Va STRIPBIN
673to the
674.Va LOCAL_ITOOLS
675.Xr make 1
676variable before running the
677.Cm distributeworld
678or
679.Cm installworld
680targets.
681See
682.Xr install 1
683for more details.
684.It Va SUBDIR_OVERRIDE
685Override the default list of sub-directories and only build the
686sub-directory named in this variable.
687If combined with
688.Cm buildworld
689then all libraries and includes, and some of the build tools will still build
690as well.
691Specifying
692.Cm -DNO_LIBS ,
693and
694.Cm -DWORLDFAST
695will only build the specified directory as was done historically.
696When combined with
697.Cm buildworld
698it is necessary to override
699.Va LOCAL_LIB_DIRS
700with any custom directories containing libraries.
701This allows building a subset of the system in the same way as
702.Cm buildworld
703does using its sysroot handling.
704This variable can also be useful when debugging failed builds.
705.Bd -literal -offset indent
706make some-target SUBDIR_OVERRIDE=foo/bar
707.Ed
708.It Va SYSDIR
709Specify the location of the kernel source to override the default
710.Pa /usr/src/sys .
711The kernel source is located in the
712.Pa sys
713subdirectory of the source tree checked out from the
714.Pa src.git
715repository.
716.It Va TARGET
717The target hardware platform.
718This is analogous to the
719.Dq Nm uname Fl m
720output.
721This is necessary to cross-build some target architectures.
722For example, cross-building for ARM64 machines requires
723.Va TARGET_ARCH Ns = Ns Li aarch64
724and
725.Va TARGET Ns = Ns Li arm64 .
726If not set,
727.Va TARGET
728defaults to the current hardware platform, unless
729.Va TARGET_ARCH
730is also set, in which case it defaults to the appropriate
731value for that architecture.
732.It Va TARGET_ARCH
733The target machine processor architecture.
734This is analogous to the
735.Dq Nm uname Fl p
736output.
737Set this to cross-build for a different architecture.
738If not set,
739.Va TARGET_ARCH
740defaults to the current machine architecture, unless
741.Va TARGET
742is also set, in which case it defaults to the appropriate
743value for that platform.
744Typically, one only needs to set
745.Va TARGET .
746.El
747.Pp
748Builds under directory
749.Pa /usr/src
750are also influenced by defining one or more of the following symbols,
751using the
752.Fl D
753option of
754.Xr make 1 :
755.Bl -tag -width ".Va LOADER_DEFAULT_INTERP"
756.It Va LOADER_DEFAULT_INTERP
757Defines what interpreter the default loader program will have.
758Valid values include
759.Dq 4th ,
760.Dq lua ,
761and
762.Dq simp .
763This creates the default link for
764.Pa /boot/loader
765to the loader with that interpreter.
766It also determines what interpreter is compiled into
767.Pa userboot .
768.It Va NO_CLEANDIR
769If set, the build targets that clean parts of the object tree use the
770equivalent of
771.Dq make clean
772instead of
773.Dq make cleandir .
774.It Va NO_CLEAN
775If set, no object tree files are cleaned at all.
776This is the default when
777.Va WITH_META_MODE
778is used with
779.Xr filemon 4
780loaded.
781See
782.Xr src.conf 5
783for more details.
784Setting
785.Va NO_CLEAN
786implies
787.Va NO_KERNELCLEAN ,
788so when
789.Va NO_CLEAN
790is set no kernel objects are cleaned either.
791.It Va NO_CTF
792If set, the build process does not run the DTrace CTF conversion tools
793on built objects.
794.It Va NO_SHARE
795If set, the build does not descend into the
796.Pa /usr/src/share
797subdirectory (i.e., manual pages, locale data files, timezone data files and
798other
799.Pa /usr/src/share
800files will not be rebuild from their sources).
801.It Va NO_KERNELCLEAN
802If set, the build process does not run
803.Dq make clean
804as part of the
805.Cm buildkernel
806target.
807.It Va NO_KERNELCONFIG
808If set, the build process does not run
809.Xr config 8
810as part of the
811.Cm buildkernel
812target.
813.It Va NO_KERNELOBJ
814If set, the build process does not run
815.Dq make obj
816as part of the
817.Cm buildkernel
818target.
819.It Va NO_LIBS
820If set, the libraries phase will be skipped.
821.It Va NO_OBJWALK
822If set, no object directories will be created.
823This should only be used if object directories were created in a
824previous build and no new directories are connected.
825.It Va UNIVERSE_TOOLCHAIN
826Requests use of the toolchain built as part of the
827.Cm universe
828target as an external toolchain.
829.It Va WORLDFAST
830If set, the build target
831.Cm buildworld
832defaults to setting
833.Va NO_CLEAN ,
834.Va NO_OBJWALK ,
835and will skip most bootstrap phases.
836It will only bootstrap libraries and build all of userland.
837This option should be used only when it is known that none of the bootstrap
838needs changed and that no new directories have been connected to the build.
839.El
840.Pp
841Builds under directory
842.Pa /usr/doc
843are influenced by the following
844.Xr make 1
845variables:
846.Bl -tag -width ".Va DOC_LANG"
847.It Va DOC_LANG
848If set, restricts the documentation build to the language subdirectories
849specified as its content.
850The default action is to build documentation for all languages.
851.El
852.Pp
853Builds using the
854.Cm universe
855and related targets are influenced by the following
856.Xr make 1
857variables:
858.Bl -tag -width ".Va USE_GCC_TOOLCHAINS"
859.It Va JFLAG
860Pass the value of this variable to each
861.Xr make 1
862invocation used to build worlds and kernels.
863This can be used to enable multiple jobs within a single architecture's build
864while still building each architecture serially.
865.It Va MAKE_JUST_KERNELS
866Only build kernels for each supported architecture.
867.It Va MAKE_JUST_WORLDS
868Only build worlds for each supported architecture.
869.It Va WITHOUT_WORLDS
870Only build kernels for each supported architecture.
871.It Va WITHOUT_KERNELS
872Only build worlds for each supported architecture.
873.It Va UNIVERSE_TARGET
874Execute the specified
875.Xr make 1
876target for each supported architecture instead of the default action of
877building a world and one or more kernels.
878This variable implies
879.Va WITHOUT_KERNELS .
880.It Va USE_GCC_TOOLCHAINS
881Use external GCC toolchains to build the requested targets.
882If the required toolchain package for a supported architecture is not installed,
883the build for that architecture is skipped.
884.Pp
885A specific version of GCC can be used by setting the value of this variable
886to the desired version
887.Pq for example, Dq gcc14 ;
888otherwise a default version of GCC is used.
889.It Va TARGETS
890Only build the listed targets instead of each supported architecture.
891.It Va EXTRA_TARGETS
892In addition to the supported architectures, build the semi-supported
893architectures.
894A semi-supported architecture has build support in the
895.Fx
896tree, but receives significantly less testing and is generally for
897fringe uses that do not have a wide appeal.
898.El
899.Sh FILES
900.Bl -tag -width ".Pa /usr/share/examples/etc/make.conf" -compact
901.It Pa /usr/doc/Makefile
902.It Pa /usr/doc/share/mk/doc.project.mk
903.It Pa /usr/ports/Mk/bsd.port.mk
904.It Pa /usr/ports/Mk/bsd.sites.mk
905.It Pa /usr/share/examples/etc/make.conf
906.It Pa /usr/src/Makefile
907.It Pa /usr/src/Makefile.inc1
908.El
909.Sh EXAMPLES
910For an
911.Dq approved
912method of updating your system from the latest sources, please see the
913.Sx COMMON ITEMS
914section in
915.Pa src/UPDATING .
916.Pp
917The following sequence of commands can be used to cross-build the system for
918the arm64 (aarch64) architecture on a different host architecture, such as
919amd64:
920.Bd -literal -offset indent
921cd /usr/src
922make TARGET=arm64 buildworld buildkernel
923make TARGET=arm64 DESTDIR=/clients/arm64 installworld installkernel
924.Ed
925.Sh SEE ALSO
926.Xr cc 1 ,
927.Xr install 1 ,
928.Xr make 1 ,
929.Xr make.conf 5 ,
930.Xr src.conf 5 ,
931.Xr arch 7 ,
932.Xr development 7 ,
933.Xr pkg 7 ,
934.Xr ports 7 ,
935.Xr release 7 ,
936.Xr tests 7 ,
937.Xr config 8 ,
938.Xr etcupdate 8 ,
939.Xr reboot 8 ,
940.Xr shutdown 8
941.Sh HISTORY
942The
943.Nm
944manpage first appeared in
945.Fx 4.3 .
946.Sh AUTHORS
947.An Mike W. Meyer Aq Mt mwm@mired.org
948