## SerenityOS build instructions

### Prerequisites

#### Linux prerequisites
Make sure you have all the dependencies installed (`ninja` is optional, but is faster in practice):

**Debian / Ubuntu**
```bash
sudo apt install build-essential cmake curl libmpfr-dev libmpc-dev libgmp-dev e2fsprogs ninja-build qemu-system-i386 qemu-utils
```

**Fedora**
```bash
sudo dnf install curl cmake mpfr-devel libmpc-devel gmp-devel e2fsprogs ninja-build patch @"C Development Tools and Libraries" @Virtualization
```

**openSUSE**
```bash
sudo zypper install curl cmake mpfr-devel mpc-devel ninja gmp-devel e2fsprogs patch qemu-x86 qemu-audio-pa gcc gcc-c++ patterns-devel-C-C++-devel_C_C++
```

**Arch Linux / Manjaro**
```bash
sudo pacman -S --needed base-devel cmake curl mpfr libmpc gmp e2fsprogs ninja qemu qemu-arch-extra
```

**ALT Linux**
```bash
apt-get install curl cmake libmpc-devel gmp-devel e2fsprogs libmpfr-devel ninja-build patch gcc
```

Ensure your gcc version is >= 10 with `gcc --version`. Otherwise, install it.

On Ubuntu it's in the repositories of 20.04 (Focal) and later - add the `ubuntu-toolchain-r/test` PPA if you're running an older version:
```bash
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
```

On Debian you can use the Debian testing branch:
```bash
sudo echo "deb http://http.us.debian.org/debian/ testing non-free contrib main" >> /etc/apt/sources.list
sudo apt update
```

Now on Ubuntu or Debian you can install gcc-10 with apt like this:
```bash
sudo apt install gcc-10 g++-10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 900 --slave /usr/bin/g++ g++ /usr/bin/g++-10
```

If you don't want to stay on the testing branch you can switch back by running:
```bash
sudo sed -i '$d' /etc/apt/sources.list
sudo apt update
```

Ensure your CMake version is >= 3.16 with `cmake --version`. If your system doesn't provide a suitable version of CMake, you can download a binary release from the [CMake website](https://cmake.org/download).

#### macOS prerequisites
Make sure you have all the dependencies installed:
```bash
brew install coreutils qemu e2fsprogs m4 autoconf libtool automake bash gcc@10 ninja
brew install --cask osxfuse
Toolchain/BuildFuseExt2.sh
```

Notes: 
- fuse-ext2 is not available as brew formula so it must be installed using `BuildFuseExt2.sh`
- Xcode and `xcode-tools` must be installed (`git` is required by some scripts)
- coreutils is needed to build gcc cross compiler
- qemu is needed to run the compiled OS image. You can also build it using the `BuildQemu.sh` script
- osxfuse, e2fsprogs, m4, autoconf, automake, libtool and `BuildFuseExt2.sh` are needed if you want to build the root filesystem disk image natively on macOS. This allows mounting an EXT2 fs and also installs commands like `mke2fs` that are not available on stock macOS. 
- bash is needed because the default version installed on macOS doesn't support globstar
- If you install some commercial EXT2 macOS fs handler instead of osxfuse and fuse-ext2, you will need to `brew install e2fsprogs` to obtain `mke2fs` anyway.
- As of 2020-08-06, you might need to tell the build system about your newer host compiler. Once you've built the toolchain, navigate to `Build/`, `rm -rf *`, then run `cmake .. -DCMAKE_C_COMPILER=gcc-10 -DCMAKE_CXX_COMPILER=g++-10`, then continue with `make install` as usual.

#### OpenBSD prerequisites
```
$ pkg_add bash gcc git gmake gmp ninja sudo
```

#### FreeBSD prerequisites
```
$ pkg add bash coreutils git gmake ninja sudo
```

#### Windows
For Windows, you will require Windows Subsystem for Linux 2 (WSL2). [Follow the WSL2 instructions here.](https://github.com/SerenityOS/serenity/blob/master/Documentation/NotesOnWSL.md)
Do note the ```Hardware acceleration``` and ```Note on filesystems``` sections, otherwise performance will be terrible.
Once you have installed a distro for WSL2, follow the Linux prerequisites above for the distro you installed, then continue as normal.

You may also want to install [ninja](https://github.com/ninja-build/ninja/releases)

### Build
Go into the `Toolchain/` directory and run the **BuildIt.sh** script:
```bash
$ cd Toolchain
$ ./BuildIt.sh
```

Building the toolchain will also automatically create a `Build/` directory for the build to live in.

Once the toolchain has been built, go into the `Build/` directory and run the commands. Note that while `ninja` seems to be faster, you can also just use GNU make, by omitting `-G Ninja` and calling `make` instead of `ninja`:
```bash
$ cd ..
$ cd Build
$ cmake .. -G Ninja
$ ninja
$ ninja install
```

This will compile all of SerenityOS and install the built files into `Root/` inside the build tree. `ninja install` actually pulls in the regular `ninja` (`ninja all`) automatically, so there isn't really a need to run it explicitly. `ninja` will automatically build as many jobs in parallel as it detects processors; `make` builds only one job in parallel. (Use the `-j` option with an argument if you want to change this.)

Now to build a disk image, run `ninja image`, and take it for a spin by using `ninja run`.
```bash
$ ninja image
$ ninja run
```

Note that the `anon` user is able to become `root` without password by default, as a development convenience.
To prevent this, remove `anon` from the `wheel` group and he will no longer be able to run `/bin/su`.

On Linux, QEMU is significantly faster if it's able to use KVM. The run script will automatically enable KVM if `/dev/kvm` exists and is readable+writable by the current user.

Bare curious users may even consider sourcing suitable hardware to [install Serenity on a physical PC.](https://github.com/SerenityOS/serenity/blob/master/Documentation/INSTALL.md)

Outside of QEMU, Serenity will run on VirtualBox. If you're curious, see how to [install Serenity on VirtualBox.](https://github.com/SerenityOS/serenity/blob/master/Documentation/VirtualBox.md)

Later on, when you `git pull` to get the latest changes, there's (usually) no need to rebuild the toolchain. You can simply run `ninja install`, `ninja image`, and `ninja run` again. CMake will only rebuild those parts that have been updated.

#### Ports
To add a package from the ports collection to Serenity, for example curl, go into `Ports/curl/` and run **./package.sh**. The sourcecode for the package will be downloaded and the package will be built. After that, run **make image** from the `Build/` directory to update the disk image. The next time you start Serenity with **make run**, `curl` will be available.