site/docs/install-compile-source.md - bazel - Git at Google

 ---
 layout: documentation
 title: Compiling Bazel from source
 ---

 <h1 id="compiling-from-source">Compiling Bazel from source</h1>

 To build Bazel from source, you can do one of the following:

 *   Build it [using an existing Bazel binary](#build-bazel-using-bazel)

 *   Build it [without an existing Bazel binary](#bootstrap-bazel) which is known
     as _bootstraping_.

 <h2 id="build-bazel-using-bazel">Build Bazel using Bazel</h2>

 If you already have a Bazel binary, you can build Bazel from a GitHub checkout.

 You will need:

 *   A GitHub checkout of Bazel's sources at the desired commit.

 *   The Bazel version that was the latest when the commit was merged. (Other
     Bazel versions may work too, but are not guaranteed to.) You can either
     download this version from
     [GitHub](https://github.com/bazelbuild/bazel/releases), or build it from
     source, or bootstrap it as described below.

 *   The same prerequisites as for bootstrapping (JDK, C++ compiler, etc.)

 Once you have a Bazel binary to build with and the source tree of Bazel, `cd`
 into the directory and run `bazel build //src:bazel`.

 <h2 id="bootstrap-bazel">Build Bazel from scratch (bootstrapping)</h2>

 You can also build Bazel from scratch, without using an existing Bazel binary.

 <h3 id="download-distfile">1. Download Bazel's sources (distribution archive)</h3>

 (This step is the same for all platforms.)

 1.  Download `bazel-<version>-dist.zip` from
     [GitHub](https://github.com/bazelbuild/bazel/releases), for example
     `bazel-0.18.0-dist.zip`.

     There is a **single, architecture-independent** distribution archive.  There
     are no architecture-specific or OS-specific distribution archives.

     You **have to use the distribution archive** to bootstrap Bazel. You cannot
     use a source tree cloned from GitHub. (The distribution archive contains
     generated source files that are required for bootstrapping and are not part
     of the normal Git source tree.)

 2.  Unpack the zip file somewhere on disk.

     We recommend to also verify the signature made by our
     [release key](https://bazel.build/bazel-release.pub.gpg) 48457EE0.

 **To build a development version** of Bazel from a GitHub checkout, you need a
 working Bazel binary. [Scroll up](#build-bazel-using-bazel) to see how to build
 Bazel using Bazel.

 <h3 id="bootstrap-unix">2. Bootstrap Bazel on Ubuntu Linux, macOS, and other Unix-like systems</h3>

 ([Scroll down](#bootstrap-windows) for instructions for Windows.)

 <h4 id="bootstrap-unix-prereq">2.1. Install the prerequisites</h4>

 *   **Bash**

 *   **zip, unzip**

 *   **C++ build toolchain**

 *   **JDK 8.** You must install version 8 of the JDK. Versions other than 8 are
     *not* supported.

 *   **Python**. Versions 2 and 3 are supported, installing one of them is
     enough.

 For example on Ubuntu Linux you can install these requirements using the
 following command:

 ```sh
 sudo apt-get install build-essential openjdk-8-jdk python zip unzip
 ```

 <h4 id="bootstrap-unix-bootstrap">2.2. Bootstrap Bazel</h4>

 1.  Open a shell or Terminal window.

 3.  `cd` to the directory where you unpacked the distribution archive.

 3.  Run the compilation script: `env EXTRA_BAZEL_ARGS="--host_javabase=@local_jdk//:jdk" bash ./compile.sh`.

 The compiled output is placed into `output/bazel`. This is a self-contained
 Bazel binary, without an embedded JDK. You can copy it anywhere or use it
 in-place. For convenience we recommend copying this binary to a directory that's
 on your `PATH` (such as `/usr/local/bin` on Linux).

 To build the `bazel` binary in a reproducible way, also set
 [`SOURCE_DATE_EPOCH`](https://reproducible-builds.org/specs/source-date-epoch/)
 in the `compile.sh` step.

 <h3 id="bootstrap-windows">2. Bootstrap Bazel on Windows</h3>

 ([Scroll up](#bootstrap-unix) for instructions for Linux, macOS, and other
 Unix-like systems.)

 <h4 id="bootstrap-windows-prereq">2.1. Install the prerequisites</h4>

 *   [MSYS2 shell](https://msys2.github.io/)

 *   **The MSYS2 packages for zip and unzip.** Run the following command in the MSYS2 shell:

     ```
     pacman -S zip unzip patch
     ```

 *   **The Visual C++ compiler.** Install the Visual C++ compiler either as part
     of Visual Studio 2015 or newer, or by installing the latest [Build Tools
     for Visual Studio 2017](https://aka.ms/BuildTools).

 *   **JDK 8.** You must install version 8 of the JDK. Versions other than 8 are
     *not* supported.

 *   **Python**. Versions 2 and 3 are supported, installing one of them is
     enough. You need the Windows-native version (downloadable from
     [https://www.python.org](https://www.python.org)).  Versions installed via
     pacman in MSYS2 will not work.

 <h4 id="bootstrap-windows-bootstrap">2.2. Bootstrap Bazel</h4>

 1.  Open the MSYS2 shell.

 2.  Set the following environment variables:
     *   Either `BAZEL_VS` or `BAZEL_VC` (they are *not* the same): Set to the
         path to the Visual Studio directory (BAZEL\_V<b>S</b>) or to the Visual
         C++ directory (BAZEL\_V<b>C</b>). Setting one of them is enough.
     *   `BAZEL_SH`: Path of the MSYS2 `bash.exe`. See the command in the
         examples below.

         Do not set this to `C:\Windows\System32\bash.exe`. (You have that file
         if you installed Windows Subsystem for Linux.) Bazel does not support
         this version of `bash.exe`.
     *   `PATH`: Add the Python directory.
     *   `JAVA_HOME`: Set to the JDK directory.

     **Example** (using BAZEL\_V<b>S</b>):

         export BAZEL_VS="C:/Program Files (x86)/Microsoft Visual Studio/2017/BuildTools"
         export BAZEL_SH="$(cygpath -m $(realpath $(which bash)))"
         export PATH="/c/python27:$PATH"
         export JAVA_HOME="C:/Program Files/Java/jdk1.8.0_112"

     or (using BAZEL\_V<b>C</b>):

         export BAZEL_VC="C:/Program Files (x86)/Microsoft Visual Studio/2017/BuildTools/VC"
         export BAZEL_SH="$(cygpath -m $(realpath $(which bash)))"
         export PATH="/c/python27:$PATH"
         export JAVA_HOME="C:/Program Files/Java/jdk1.8.0_112"

 3.  `cd` to the directory where you unpacked the distribution archive.

 4.  Run the compilation script: `./compile.sh`

 The compiled output is placed into `output/bazel.exe`. This is a self-contained
 Bazel binary, without an embedded JDK. You can copy it anywhere or use it
 in-place. For convenience we recommend copying this binary to a directory that's
 on your `PATH`.

 You don't need to run Bazel from the MSYS2 shell. You can run Bazel from the
 Command Prompt (`cmd.exe`) or PowerShell.
	---
	layout: documentation
	title: Compiling Bazel from source
	---

	<h1 id="compiling-from-source">Compiling Bazel from source</h1>

	To build Bazel from source, you can do one of the following:

	* Build it [using an existing Bazel binary](#build-bazel-using-bazel)

	* Build it [without an existing Bazel binary](#bootstrap-bazel) which is known
	as _bootstraping_.

	<h2 id="build-bazel-using-bazel">Build Bazel using Bazel</h2>

	If you already have a Bazel binary, you can build Bazel from a GitHub checkout.

	You will need:

	* A GitHub checkout of Bazel's sources at the desired commit.

	* The Bazel version that was the latest when the commit was merged. (Other
	Bazel versions may work too, but are not guaranteed to.) You can either
	download this version from
	[GitHub](https://github.com/bazelbuild/bazel/releases), or build it from
	source, or bootstrap it as described below.

	* The same prerequisites as for bootstrapping (JDK, C++ compiler, etc.)

	Once you have a Bazel binary to build with and the source tree of Bazel, `cd`
	into the directory and run `bazel build //src:bazel`.

	<h2 id="bootstrap-bazel">Build Bazel from scratch (bootstrapping)</h2>

	You can also build Bazel from scratch, without using an existing Bazel binary.

	<h3 id="download-distfile">1. Download Bazel's sources (distribution archive)</h3>

	(This step is the same for all platforms.)

	1. Download `bazel-<version>-dist.zip` from
	[GitHub](https://github.com/bazelbuild/bazel/releases), for example
	`bazel-0.18.0-dist.zip`.

	There is a single, architecture-independent distribution archive. There
	are no architecture-specific or OS-specific distribution archives.

	You have to use the distribution archive to bootstrap Bazel. You cannot
	use a source tree cloned from GitHub. (The distribution archive contains
	generated source files that are required for bootstrapping and are not part
	of the normal Git source tree.)

	2. Unpack the zip file somewhere on disk.

	We recommend to also verify the signature made by our
	[release key](https://bazel.build/bazel-release.pub.gpg) 48457EE0.

	To build a development version of Bazel from a GitHub checkout, you need a
	working Bazel binary. [Scroll up](#build-bazel-using-bazel) to see how to build
	Bazel using Bazel.

	<h3 id="bootstrap-unix">2. Bootstrap Bazel on Ubuntu Linux, macOS, and other Unix-like systems</h3>

	([Scroll down](#bootstrap-windows) for instructions for Windows.)

	<h4 id="bootstrap-unix-prereq">2.1. Install the prerequisites</h4>

	* Bash

	* zip, unzip

	* C++ build toolchain

	* JDK 8. You must install version 8 of the JDK. Versions other than 8 are
	not supported.

	* Python. Versions 2 and 3 are supported, installing one of them is
	enough.

	For example on Ubuntu Linux you can install these requirements using the
	following command:

	```sh
	sudo apt-get install build-essential openjdk-8-jdk python zip unzip
	```

	<h4 id="bootstrap-unix-bootstrap">2.2. Bootstrap Bazel</h4>

	1. Open a shell or Terminal window.

	3. `cd` to the directory where you unpacked the distribution archive.

	3. Run the compilation script: `env EXTRA_BAZEL_ARGS="--host_javabase=@local_jdk//:jdk" bash ./compile.sh`.

	The compiled output is placed into `output/bazel`. This is a self-contained
	Bazel binary, without an embedded JDK. You can copy it anywhere or use it
	in-place. For convenience we recommend copying this binary to a directory that's
	on your `PATH` (such as `/usr/local/bin` on Linux).

	To build the `bazel` binary in a reproducible way, also set
	[`SOURCE_DATE_EPOCH`](https://reproducible-builds.org/specs/source-date-epoch/)
	in the `compile.sh` step.

	<h3 id="bootstrap-windows">2. Bootstrap Bazel on Windows</h3>

	([Scroll up](#bootstrap-unix) for instructions for Linux, macOS, and other
	Unix-like systems.)

	<h4 id="bootstrap-windows-prereq">2.1. Install the prerequisites</h4>

	* [MSYS2 shell](https://msys2.github.io/)

	* The MSYS2 packages for zip and unzip. Run the following command in the MSYS2 shell:

	```
	pacman -S zip unzip patch
	```

	* The Visual C++ compiler. Install the Visual C++ compiler either as part
	of Visual Studio 2015 or newer, or by installing the latest [Build Tools
	for Visual Studio 2017](https://aka.ms/BuildTools).

	* JDK 8. You must install version 8 of the JDK. Versions other than 8 are
	not supported.

	* Python. Versions 2 and 3 are supported, installing one of them is
	enough. You need the Windows-native version (downloadable from
	[https://www.python.org](https://www.python.org)). Versions installed via
	pacman in MSYS2 will not work.

	<h4 id="bootstrap-windows-bootstrap">2.2. Bootstrap Bazel</h4>

	1. Open the MSYS2 shell.

	2. Set the following environment variables:
	* Either `BAZEL_VS` or `BAZEL_VC` (they are not the same): Set to the
	path to the Visual Studio directory (BAZEL\_V<b>S</b>) or to the Visual
	C++ directory (BAZEL\_V<b>C</b>). Setting one of them is enough.
	* `BAZEL_SH`: Path of the MSYS2 `bash.exe`. See the command in the
	examples below.

	Do not set this to `C:\Windows\System32\bash.exe`. (You have that file
	if you installed Windows Subsystem for Linux.) Bazel does not support
	this version of `bash.exe`.
	* `PATH`: Add the Python directory.
	* `JAVA_HOME`: Set to the JDK directory.

	Example (using BAZEL\_V<b>S</b>):

	export BAZEL_VS="C:/Program Files (x86)/Microsoft Visual Studio/2017/BuildTools"
	export BAZEL_SH="$(cygpath -m $(realpath $(which bash)))"
	export PATH="/c/python27:$PATH"
	export JAVA_HOME="C:/Program Files/Java/jdk1.8.0_112"

	or (using BAZEL\_V<b>C</b>):

	export BAZEL_VC="C:/Program Files (x86)/Microsoft Visual Studio/2017/BuildTools/VC"
	export BAZEL_SH="$(cygpath -m $(realpath $(which bash)))"
	export PATH="/c/python27:$PATH"
	export JAVA_HOME="C:/Program Files/Java/jdk1.8.0_112"

	3. `cd` to the directory where you unpacked the distribution archive.

	4. Run the compilation script: `./compile.sh`

	The compiled output is placed into `output/bazel.exe`. This is a self-contained
	Bazel binary, without an embedded JDK. You can copy it anywhere or use it
	in-place. For convenience we recommend copying this binary to a directory that's
	on your `PATH`.

	You don't need to run Bazel from the MSYS2 shell. You can run Bazel from the
	Command Prompt (`cmd.exe`) or PowerShell.