modules.order¶

This file records the order in which modules appear in Makefiles. Thisis used by modprobe to deterministically resolve aliases that matchmultiple modules.

modules.builtin¶

This file lists all modules that are built into the kernel. This is usedby modprobe to not fail when trying to load something builtin.

modules.builtin.modinfo¶

This file contains modinfo from all modules that are built into the kernel.Unlike modinfo of a separate module, all fields are prefixed with module name.

modules.builtin.ranges¶

This file contains address offset ranges (per ELF section) for all modulesthat are built into the kernel. Together with System.map, it can be usedto associate module names with symbols.

KCPPFLAGS¶

Additional options to pass when preprocessing. The preprocessing optionswill be used in all cases where kbuild does preprocessing includingbuilding C files and assembler files.

KAFLAGS¶

Additional options to the assembler (for built-in and modules).

AFLAGS_MODULE¶

Additional assembler options for modules.

AFLAGS_KERNEL¶

Additional assembler options for built-in.

KCFLAGS¶

Additional options to the C compiler (for built-in and modules).

KRUSTFLAGS¶

Additional options to the Rust compiler (for built-in and modules).

CFLAGS_KERNEL¶

Additional options for $(CC) when used to compilecode that is compiled as built-in.

CFLAGS_MODULE¶

Additional module specific options to use for $(CC).

RUSTFLAGS_KERNEL¶

Additional options for $(RUSTC) when used to compilecode that is compiled as built-in.

RUSTFLAGS_MODULE¶

Additional module specific options to use for $(RUSTC).

LDFLAGS_MODULE¶

Additional options used for $(LD) when linking modules.

HOSTCFLAGS¶

Additional flags to be passed to $(HOSTCC) when building host programs.

HOSTCXXFLAGS¶

Additional flags to be passed to $(HOSTCXX) when building host programs.

HOSTRUSTFLAGS¶

Additional flags to be passed to $(HOSTRUSTC) when building host programs.

PROCMACROLDFLAGS¶

Flags to be passed when linking Rust proc macros. Since proc macros are loadedby rustc at build time, they must be linked in a way that is compatible withthe rustc toolchain being used.

For instance, it can be useful when rustc uses a different C library thanthe one the user wants to use for host programs.

If unset, it defaults to the flags passed when linking host programs.

HOSTLDFLAGS¶

Additional flags to be passed when linking host programs.

HOSTLDLIBS¶

Additional libraries to link against when building host programs.

USERCFLAGS¶

Additional options used for $(CC) when compiling userprogs.

USERLDFLAGS¶

Additional options used for $(LD) when linking userprogs. userprogs are linkedwith CC, so $(USERLDFLAGS) should include “-Wl,” prefix as applicable.

KBUILD_KCONFIG¶

Set the top-level Kconfig file to the value of this environmentvariable. The default name is “Kconfig”.

KBUILD_VERBOSE¶

Set the kbuild verbosity. Can be assigned same values as “V=...”.

See make help for the full list.

Setting “V=...” takes precedence over KBUILD_VERBOSE.

KBUILD_EXTMOD¶

Set the directory to look for the kernel source when building externalmodules.

Setting “M=...” takes precedence over KBUILD_EXTMOD.

KBUILD_OUTPUT¶

Specify the output directory when building the kernel.

This variable can also be used to point to the kernel output directory whenbuilding external modules against a pre-built kernel in a separate builddirectory. Please note that this does NOT specify the output directory for theexternal modules themselves. (Use KBUILD_EXTMOD_OUTPUT for that purpose.)

The output directory can also be specified using “O=...”.

Setting “O=...” takes precedence over KBUILD_OUTPUT.

KBUILD_EXTMOD_OUTPUT¶

Specify the output directory for external modules.

Setting “MO=...” takes precedence over KBUILD_EXTMOD_OUTPUT.

KBUILD_EXTRA_WARN¶

Specify the extra build checks. The same value can be assigned by passingW=... from the command line.

Seemake help for the list of the supported values.

Setting “W=...” takes precedence over KBUILD_EXTRA_WARN.

KBUILD_DEBARCH¶

For the deb-pkg target, allows overriding the normal heuristics deployed bydeb-pkg. Normally deb-pkg attempts to guess the right architecture based onthe UTS_MACHINE variable, and on some architectures also the kernel config.The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debianarchitecture.

KDOCFLAGS¶

Specify extra (warning/error) flags for kernel-doc checks during the build,see scripts/kernel-doc for which flags are supported. Note that this doesn’t(currently) apply to documentation builds.

ARCH¶

Set ARCH to the architecture to be built.

In most cases the name of the architecture is the same as thedirectory name found in the arch/ directory.

But some architectures such as x86 and sparc have aliases.

• x86: i386 for 32 bit, x86_64 for 64 bit

• parisc: parisc64 for 64 bit

• sparc: sparc32 for 32 bit, sparc64 for 64 bit

CROSS_COMPILE¶

Specify an optional fixed part of the binutils filename.CROSS_COMPILE can be a part of the filename or the full path.

CROSS_COMPILE is also used for ccache in some setups.

CF¶

Additional options for sparse.

CF is often used on the command-line like this:

make CF=-Wbitwise C=2

INSTALL_PATH¶

INSTALL_PATH specifies where to place the updated kernel and system mapimages. Default is /boot, but you can set it to other values.

INSTALLKERNEL¶

Install script called when using “make install”.The default name is “installkernel”.

The script will be called with the following arguments:

• $1 - kernel version

• $2 - kernel image file

• $3 - kernel map file

• $4 - default install path (use root directory if blank)

The implementation of “make install” is architecture specificand it may differ from the above.

INSTALLKERNEL is provided to enable the possibility tospecify a custom installer when cross compiling a kernel.

MODLIB¶

Specify where to install modules.The default value is:

$(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)

The value can be overridden in which case the default value is ignored.

INSTALL_MOD_PATH¶

INSTALL_MOD_PATH specifies a prefix to MODLIB for module directoryrelocations required by build roots. This is not defined in themakefile but the argument can be passed to make if needed.

INSTALL_MOD_STRIP¶

INSTALL_MOD_STRIP, if defined, will cause modules to bestripped after they are installed. If INSTALL_MOD_STRIP is ‘1’, thenthe default option --strip-debug will be used. Otherwise,INSTALL_MOD_STRIP value will be used as the options to the strip command.

INSTALL_HDR_PATH¶

INSTALL_HDR_PATH specifies where to install user space headers whenexecuting “make headers_*”.

The default value is:

$(objtree)/usr

$(objtree) is the directory where output files are saved.The output directory is often set using “O=...” on the commandline.

The value can be overridden in which case the default value is ignored.

INSTALL_DTBS_PATH¶

INSTALL_DTBS_PATH specifies where to install device tree blobs forrelocations required by build roots. This is not defined in themakefile but the argument can be passed to make if needed.

KBUILD_ABS_SRCTREE¶

Kbuild uses a relative path to point to the tree when possible. For instance,when building in the source tree, the source tree path is ‘.’

Setting this flag requests Kbuild to use absolute path to the source tree.There are some useful cases to do so, like when generating tag files withabsolute path entries etc.

KBUILD_SIGN_PIN¶

This variable allows a passphrase or PIN to be passed to the sign-fileutility when signing kernel modules, if the private key requires such.

KBUILD_MODPOST_WARN¶

KBUILD_MODPOST_WARN can be set to avoid errors in case of undefinedsymbols in the final module linking stage. It changes such errorsinto warnings.

KBUILD_MODPOST_NOFINAL¶

KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.This is solely useful to speed up test compiles.

KBUILD_EXTRA_SYMBOLS¶

For modules that use symbols from other modules.See more details inBuilding External Modules.

ALLSOURCE_ARCHS¶

For tags/TAGS/cscope targets, you can specify more than one archto be included in the databases, separated by blank space. E.g.:

$ make ALLSOURCE_ARCHS="x86 mips arm" tags

To get all available archs you can also specify all. E.g.:

$ make ALLSOURCE_ARCHS=all tags

IGNORE_DIRS¶

For tags/TAGS/cscope targets, you can choose which directories won’tbe included in the databases, separated by blank space. E.g.:

$ make IGNORE_DIRS="drivers/gpu/drm/radeon tools" cscope

KBUILD_BUILD_TIMESTAMP¶

Setting this to a date string overrides the timestamp used in theUTS_VERSION definition (uname -v in the running kernel). The value has tobe a string that can be passed to date -d. E.g.:

$ KBUILD_BUILD_TIMESTAMP="Mon Oct 13 00:00:00 UTC 2025" make

The default value is the output of the date command at one point duringbuild. If provided, this timestamp will also be used for mtime fieldswithin any initramfs archive. Initramfs mtimes are 32-bit, so dates beforethe 1970 Unix epoch, or after 2106-02-07 06:28:15 UTC will fail.

KBUILD_BUILD_USER, KBUILD_BUILD_HOST¶

These two variables allow to override theuser@host string displayed duringboot and in /proc/version. The default value is the output of the commandswhoami and host, respectively.

LLVM¶

If this variable is set to 1, Kbuild will use Clang and LLVM utilities insteadof GCC and GNU binutils to build the kernel.