limine/README.md

# Limine

### What is Limine?

Limine is a modern, advanced x86/x86_64 BIOS/UEFI multiprotocol bootloader used
as the reference implementation for the
[stivale protocols](https://github.com/stivale/stivale).

### Support Limine
Like Limine and want to support it? Donate Bitcoin to
`bc1q00d59y75crpapw7qp8sea5j5sx6l4k2ssjylf9` :)

### Limine's boot menu

![Reference screenshot](/screenshot.png?raw=true "Reference screenshot")

[Photo by Chris Kane from Pexels](https://www.pexels.com/photo/reflection-of-building-on-body-of-water-at-daytime-166360/)

### Supported boot protocols
* stivale and stivale2 (Limine's native boot protocols, see [their specifications](https://github.com/stivale/stivale) for details)
* Linux
* Multiboot 1
* Chainloading

### Supported filesystems
* ext2/3/4
* echfs
* FAT12/16/32
* ISO9660 (CDs/DVDs)

### Supported partitioning schemes
* MBR
* GPT
* Unpartitioned media

## Binary releases

For convenience, for point releases, binaries are distributed. These binaries
are shipped in the `-binary` branches and tags of this repository
(see [branches](https://github.com/limine-bootloader/limine/branches/all) and
[tags](https://github.com/limine-bootloader/limine/tags)).

For example, to clone the latest binary release of the `v2.x` branch one can do
```bash
git clone https://github.com/limine-bootloader/limine.git --branch=v2.0-branch-binary --depth=1
```
or, to clone a specific binary point release (for example v2.40)
```bash
git clone https://github.com/limine-bootloader/limine.git --branch=v2.40-binary --depth=1
```

Additionally, the absolute latest Limine binary release can be obtained by
fetching the `latest-binary` branch:
```bash
git clone https://github.com/limine-bootloader/limine.git --branch=latest-binary --depth=1
```

`limine-install` binaries are provided for Linux and Windows.

In case one wants to rebuild `limine-install`, simply use `make` in the binary
release.

## Building the bootloader

*These steps are not necessary if cloning a binary release. If so, skip to*
*"Installing Limine binaries".*

**Note that the build system does not support building from a directory whose**
**full path contains spaces.**

### Building the toolchain

This step can take a long time, but it will ensure that the toolchain will work
with Limine. If on an x86_64 host, with GCC or Clang installed, you can skip to
the next paragraph in order to use the system's toolchain instead.

The toolchain's build process depends on the following packages: `GNU make`,
`curl`, `gzip`, `bzip2`, `gcc/clang`, `g++/clang++`.

Building the toolchain can be accomplished by running:
```bash
make toolchain    # (or gmake where applicable)
```

### Building Limine

In order to build Limine, the following packages have to be installed:
`GNU make`, `git`, `nasm`, `mtools` (optional, necessary to build
`limine-eltorito-efi.bin`).
Furthermore, either the toolchain must have been built in the previous
paragraph, or `gcc` or `llvm/clang` must also be installed.
`GNU binutils` is necessary in order to build the UEFI ports of Limine. A full
LLVM toolchain without `GNU binutils` can be used to build just the BIOS port
instead.

Both the UEFI and BIOS ports of the bootloader can be built, using
`GCC/GNU binutils` (which includes the shipped toolchain), with:
```bash
make    # (or gmake where applicable)
```

It is possible to pass `make` additional flags, most relevantly,
`TOOLCHAIN=`, which allows one to specify an alternative toolchain for the build
system to use (the default is `limine`, resulting in program names like `limine-gcc`,
falling back to no-prefix, or host, toolchain).

The generated bootloader files are going to be in `bin`.

#### Using clang/LLVM

In order to build the BIOS port fully using clang/LLVM, run `make` as such:
```bash
# (or gmake where applicable)
make limine-bios bin/limine-install CC="clang" TOOLCHAIN="llvm" TOOLCHAIN_CC="clang" TOOLCHAIN_LD="ld.lld"
```

And in order to build the UEFI port using clang/LLVM + `GNU binutils`, run
`make` as such:
```bash
# (or gmake where applicable)
make limine-uefi TOOLCHAIN="llvm" TOOLCHAIN_CC="clang" TOOLCHAIN_LD="ld" TOOLCHAIN_OBJCOPY="objcopy"
```

Where `ld` and `objcopy` refer to GNU binutils versions of them. Specify their
full path if necessary.

## Installing Limine binaries

This step is optional as the bootloader binaries can be used from the `bin` or
release directory just fine. This step will only install them to a `share` and
`bin` directories in the specified `PREFIX` (default is `/usr/local`).

Use `make install` to install the Limine binaries, optionally specifying a
different prefix with `make install PREFIX=/myprefix`.

## How to use

### UEFI
The `BOOTX64.EFI` file is a vaild EFI application that can be simply copied to
the `/EFI/BOOT` directory of a FAT formatted EFI system partition. This file can
be installed there and coexist with a BIOS installation of Limine (see below) so
that the disk will be bootable on both BIOS and UEFI systems.

The boot device must to contain the `limine.cfg` file in
either the root or the `boot` directory of one of the partitions, formatted
with a supported file system (the ESP partition is recommended).

### BIOS/MBR
In order to install Limine on a MBR device (which can just be a raw image file),
run `limine-install` as such:

```bash
limine-install <path to device/image>
```

The boot device must to contain the `limine.sys` and `limine.cfg` files in
either the root or the `boot` directory of one of the partitions, formatted
with a supported file system.

### BIOS/GPT
If using a GPT formatted device, there are 2 options one can follow for
installation:
* Specifying a dedicated stage 2 partition.
* Letting `limine-install` attempt to embed stage 2 within GPT structures.

In case one wants to specify a stage 2 partition, create a partition on the GPT
device of at least 32KiB in size, and pass the 1-based number of the partition
to `limine-install` as a second argument; such as:

```bash
limine-install <path to device/image> <1-based stage 2 partition number>
```

In case one wants to let `limine-install` embed stage 2 within GPT's structures,
simply omit the partition number, and invoke `limine-install` the same as one
would do for an MBR partitioned device.

The boot device must to contain the `limine.sys` and `limine.cfg` files in
either the root or the `boot` directory of one of the partitions, formatted
with a supported file system.

### BIOS/UEFI hybrid ISO creation
In order to create a hybrid ISO with Limine, place the
`limine-eltorito-efi.bin`, `limine-cd.bin`, `limine.sys`, and `limine.cfg` files
into a directory which will serve as the root of the created ISO.
(`limine.sys` and `limine.cfg` must either be in the root or inside a `boot`
subdirectory; `limine-eltorito-efi.bin` and `limine-cd.bin` can reside
anywhere).

Place any other file you want to be on the final ISO in said directory, then
run:
```
xorriso -as mkisofs -b <relative path of limine-cd.bin> \
        -no-emul-boot -boot-load-size 4 -boot-info-table \
        --efi-boot <relative path of limine-eltorito-efi.bin> \
        -efi-boot-part --efi-boot-image --protective-msdos-label \
        <root directory> -o image.iso
```

*Note: `xorriso` is required.*

And do not forget to also run `limine-install` on the generated image:
```
limine-install image.iso
```

`<relative path of limine-cd.bin>` is the relative path of
`limine-cd.bin` inside the root directory.
For example, if it was copied in `<root directory>/boot/limine-cd.bin`,
it would be `boot/limine-cd.bin`.

`<relative path of limine-eltorito-efi.bin>` is the relative path of
`limine-eltorito-efi.bin` inside the root directory.
For example, if it was copied in
`<root directory>/boot/limine-eltorito-efi.bin`, it would be
`boot/limine-eltorito-efi.bin`.

### BIOS/PXE boot
The `limine-pxe.bin` binary is a valid PXE boot image.
In order to boot Limine from PXE it is necessary to setup a DHCP server with
support for PXE booting. This can either be accomplished using a single DHCP
server or your existing DHCP server and a proxy DHCP server such as dnsmasq.

`limine.cfg` and `limine.sys` are expected to be on the server used for boot.

### Configuration
The `limine.cfg` file contains Limine's configuration.

An example `limine.cfg` file can be found in `test/limine.cfg`.

More info on the format of `limine.cfg` can be found in `CONFIG.md`.

## Acknowledgments
Limine uses a stripped-down version of [tinf](https://github.com/jibsen/tinf).

## Discord server
We have a [Discord server](https://discord.gg/QEeZMz4) if you need support,
info, or you just want to hang out with us.