-*- Text -*-

This is the GRUB.  Welcome.

This file contains instructions for compiling and installing the GRUB.

Where this document refers to packages names, they are named according to the
Debian 11 package repositories. These packages can be found by searching
https://packages.debian.org/.

The Requirements
================

GRUB depends on some software packages installed into your system. If
you don't have any of them, please obtain and install them before
configuring the GRUB.

* GCC 5.1.0 or later
  Experimental support for clang 8.0.0 or later (results in much bigger binaries)
  for i386, x86_64, arm (including thumb), arm64, mips(el), powerpc, sparc64
* GNU Make
* GNU Bison 2.3 or later
* GNU gettext
* GNU binutils 2.9.1.0.23 or later
* Flex 2.5.35 or later
* pkg-config
* GNU patch
* Other standard GNU/Unix tools
* a libc with large file support (e.g. glibc 2.1 or later)

On GNU/Linux, you also need:

* libdevmapper 1.02.34 or later (recommended)

For optional grub-emu features, you need:

* SDL (recommended)
* libpciaccess (optional)

To build GRUB's graphical terminal (gfxterm), you need:

* FreeType 2.1.5 or later
* GNU Unifont

To build grub-mkfont the unicode fonts are required (xfonts-unifont package
on Debian).

If you use a development snapshot or want to hack on GRUB you may
need the following.

* Python 3 (NOTE: python 2.6 should still work, but it's not tested)
* Autoconf 2.64 or later
* Automake 1.14 or later

Your distro may package cross-compiling toolchains such as the following
incomplete list on Debian: gcc-aarch64-linux-gnu, gcc-arm-linux-gnueabihf,
gcc-mips-linux-gnu, gcc-mipsel-linux-gnu, gcc-powerpc64-linux-gnu,
gcc-riscv64-linux-gnu, gcc-sparc64-linux-gnu, mingw-w64 and mingw-w64-tools.

More cross compiling toolchains can be found at the following trusted sites:

* https://mirrors.kernel.org/pub/tools/crosstool/
* https://toolchains.bootlin.com/

Prerequisites for make-check:

* qemu, specifically the binary "qemu-system-ARCH" where ARCH is the
  architecture GRUB has been built for; the "qemu-system" package on Debian
  will install all needed qemu architectures
* OVMF, for EFI platforms (packages ovmf, ovmf-ia32, qemu-efi-arm, and
  qemu-efi-aarch64)
* OpenBIOS, for ieee1275 platforms (packages openbios-ppc and openbios-sparc)
* xorriso 1.2.9 or later, for grub-mkrescue and grub-shell
* wamerican, for grub-fs-tester
* mtools, FAT tools for EFI platforms
* xfonts-unifont, for the functional tests

* If running a Linux kernel the following modules must be loaded:
  - fuse, loop
  - btrfs, erofs, ext4, f2fs, fat, hfs, hfsplus, jfs, mac-roman, minix, nilfs2,
    reiserfs, udf, xfs
  - On newer kernels, the exfat kernel modules may be used instead of the
    exfat FUSE filesystem
* The following are Debian named packages required mostly for the full
  suite of filesystem testing (but some are needed by other tests as well):
  - btrfs-progs, dosfstools, e2fsprogs, erofs-utils, exfatprogs, exfat-fuse,
    f2fs-tools, genromfs, hfsprogs, jfsutils, nilfs-tools, ntfs-3g,
    reiserfsprogs, squashfs-tools, reiserfsprogs, udftools, xfsprogs, zfs-fuse
  - exfat-fuse, if not using the exfat kernel module
  - gzip, lzop, xz-utils
  - attr, cpio, g++, gawk, parted, recode, tar, util-linux

Note that `make check' will run and many tests may complete successfully
with only a subset of these prerequisites. However, some tests may be
skipped or fail due to missing prerequisites.

To build the documentation you'll need:
* texinfo, for the info and html documentation
* texlive, for building the dvi and pdf documentation (optional)

To use the gdb_grub GDB script you'll need:
* readelf (binutils package)
* objdump (binutils package)
* GNU Debugger > 7, built with python support (gdb package)
* Python >= 3.5 (python3 package)

Configuring the GRUB
====================

The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation.  It uses
those values to create a `Makefile' in each directory of the package.
It may also create one or more `.h' files containing system-dependent
definitions.  Finally, it creates a shell script `config.status' that
you can run in the future to recreate the current configuration, a
file `config.cache' that saves the results of its tests to speed up
reconfiguring, and a file `config.log' containing compiler output
(useful mainly for debugging `configure').

If you need to do unusual things to compile the package, please try to
figure out how `configure' could check whether to do them, and mail
diffs or instructions to the address given in the `README' so they can
be considered for the next release.  If at some point `config.cache'
contains results you don't want to keep, you may remove or edit it.

The file `configure.ac' is used to create `configure' by a program
called `autoconf'.  You only need `configure.in' if you want to change
it or regenerate `configure' using a newer version of `autoconf'.


Building the GRUB
=================

The simplest way to compile this package is:

  1. `cd' to the directory containing the package's source code.

  2. Skip this and following step if you use release tarball and proceed to
     step 4. If you want translations type `./linguas.sh'.
  
  3. Type `./bootstrap'.

     The autogen.sh (called by bootstrap) uses python. By default autodetect
     it, but it can be overridden by setting the PYTHON variable.

  4. Type `./configure' to configure the package for your system.
     If you're using `csh' on an old version of System V, you might
     need to type `sh ./configure' instead to prevent `csh' from trying
     to execute `configure' itself.

     Running `configure' takes awhile.  While running, it prints some
     messages telling which features it is checking for.

  6. Type `make' to compile the package.

  7. Optionally, type `make check' to run any self-tests that come with
     the package. Note that many of the tests require root privileges in
     order to run.

  8. Type `make install' to install the programs and any data files and
     documentation.

  9. Type `make html' or `make pdf' to generate the html or pdf
     documentation.  Note, these are not built by default.

 10. You can remove the program binaries and object files from the
     source code directory by typing `make clean'.  To also remove the
     files that `configure' created (so you can compile the package for
     a different kind of computer), type `make distclean'.  There is
     also a `make maintainer-clean' target, but that is intended mainly
     for the package's developers.  If you use it, you may have to get
     all sorts of other programs in order to regenerate files that came
     with the distribution.

Cross-compiling the GRUB
========================

GRUB defines 3 platforms:

  - "Build" is the one which build systems runs on.
  - "Host" is where you execute GRUB utils.
  - "Target" is where GRUB itself runs.

For grub-emu host and target must be the same but may differ from build.

If build and host are different make check isn't available.

If build and host are different man pages are not generated.

As an example imagine you have a build system running on FreeBSD on sparc
which prepares packages for developers running amd64 GNU/Linux laptop and
they need to make images for ARM board running U-boot. In this case:

build=sparc64-freebsd
host=amd64-linux-gnu
target=arm-uboot

For this example the configure line might look like (more details below)
(some options are optional and included here for completeness but some rarely
used options are omitted):

  ./configure --build=sparc64-freebsd --host=x86_64-linux-gnu \
    --target=arm-linux-gnueabihf --with-platform=efi \
    BUILD_CC=gcc BUILD_PKG_CONFIG=pkg-config \
    HOST_CC=x86_64-linux-gnu-gcc HOST_CFLAGS='-g -O2' \
    PKG_CONFIG=x86_64-linux-gnu-pkg-config TARGET_CC=arm-linux-gnueabihf-gcc \
    TARGET_CFLAGS='-Os -march=armv8.3-a' TARGET_CCASFLAGS='-march=armv8.3-a' \
    TARGET_OBJCOPY=arm-linux-gnueabihf-objcopy \
    TARGET_STRIP=arm-linux-gnueabihf-strip TARGET_NM=arm-linux-gnueabihf-nm \
    TARGET_RANLIB=arm-linux-gnueabihf-ranlib LEX=flex

Note, that the autoconf 2.65 manual states that when using the --host argument
to configure, the --build argument should be specified as well. Not sending
--build, enters a compatibility mode that will be removed in the future.

Normally, for building a GRUB on amd64 with tools to run on amd64 to
generate images to run on ARM, using your Linux distribution's
packaged cross compiler, the following would suffice:

  ./configure --target=arm-linux-gnueabihf --with-platform=efi

You need to use following options to specify tools and platforms. For minimum
version look at prerequisites. All tools not mentioned in this section under
corresponding platform are not needed for the platform in question.

  - For build
    1. --build= to autoconf name of build.
    2. BUILD_CC= to gcc able to compile for build. This is used, for
       example, to compile build-gentrigtables which is then run to
       generate sin and cos tables.
    3. BUILD_CFLAGS= for C options for build.
    4. BUILD_CPPFLAGS= for C preprocessor options for build.
    5. BUILD_LDFLAGS= for linker options for build.
    6. BUILD_PKG_CONFIG= for pkg-config for build (optional).

  - For host
    1. --host= to autoconf name of host.
    2. CC= for gcc able to compile for host.
    3. CFLAGS= for C options for host.
    4. HOST_CC= for gcc able to compile for host.
    5. HOST_CFLAGS= for C options for host.
    6. HOST_CPPFLAGS= for C preprocessor options for host.
    7. HOST_LDFLAGS= for linker options for host.
    8. PKG_CONFIG= for pkg-config for host (optional).
    9. Libdevmapper if any must be in standard linker folders (-ldevmapper) (optional).
    10. Libfuse if any must be in standard linker folders (-lfuse) (optional).
    11. Libzfs if any must be in standard linker folders (-lzfs) (optional).
    12. Liblzma if any must be in standard linker folders (-llzma) (optional).
    Note: The HOST_* variables override not prefixed variables.

  - For target
    1. --target= to autoconf cpu name of target.
    2. --with-platform to choose firmware.
    3. TARGET_CC= for gcc able to compile for target.
    4. TARGET_CFLAGS= for C options for target.
    5. TARGET_CPPFLAGS= for C preprocessor options for target.
    6. TARGET_CCASFLAGS= for assembler options for target.
    7. TARGET_LDFLAGS= for linker options for target.
    8. TARGET_OBJCOPY= for objcopy for target.
    9. TARGET_STRIP= for strip for target.
    10. TARGET_NM= for nm for target.
    11. TARGET_RANLIB= for ranlib for target.
    Note: If the TARGET_* variables are not specified then they will default
          to be the same as the host variables. If host variables are not
          specified then the TARGET_* variables will default to be the same
          as not prefixed variables.

  - Additionally for emu, for host and target.
    1. SDL is looked for in standard linker directories (-lSDL) (optional)
    2. libpciaccess is looked for in standard linker directories (-lpciaccess) (optional)

  - Platform-agnostic tools and data.
    1. make is the tool you execute after ./configure.
    2. Bison is specified in YACC= variable
    3. Flex is specified in LEX= variable
    4. GNU unifont and Djvu sans are looked for in standard directories.

Compiling For Multiple Architectures
====================================

You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  `cd' to the directory where you want the object files
and executables to go and run the `configure' script.  `configure'
automatically checks for the source code in the directory that
`configure' is in and in `..'.


Installation Names
==================

By default, `make install' will install the package's files in
`/usr/local/bin', `/usr/local/man', etc.  You can specify an
installation prefix by giving `configure' the option `--prefix=PATH'.

You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.  If
you give `configure' the option `--exec-prefix=PATH', the package will
use PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.

In addition, if you use an unusual directory layout you can give
options like `--bindir=PATH' to specify different values for
particular kinds of files.  Run `configure --help' for a list of the
directories you can set and what kinds of files go in them.

If the package supports it, you can cause programs to be installed
with an extra prefix or suffix on their names by giving `configure'
the option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.

Please note, however, that the GRUB knows where it is located in the
filesystem.  If you have installed it in an unusual location, the
system might not work properly, or at all.  The chief utility of these
options for the GRUB is to allow you to "install" in some alternate
location, and then copy these to the actual root filesystem later.


Sharing Defaults
================

If you want to set default values for `configure' scripts to share,
you can create a site shell script called `config.site' that gives
default values for variables like `CC', `cache_file', and `prefix'.
`configure' looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists.  Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: not all `configure' scripts look for a site script.


Operation Controls
==================

   `configure' recognizes the following options to control how it
operates.

`--cache-file=FILE'
     Use and save the results of the tests in FILE instead of
     `./config.cache'.  Set FILE to `/dev/null' to disable caching, for
     debugging `configure'.

`--help'
     Print a summary of the options to `configure', and exit.

`--quiet'
`--silent'
`-q'
     Do not print messages saying which checks are being made.

`--srcdir=DIR'
     Look for the package's source code in directory DIR.  Usually
     `configure' can determine that directory automatically.

`--version'
     Print the version of Autoconf used to generate the `configure'
     script, and exit.