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go/doc/install-source.html
Giovanni Bajo 2ba00e4754 doc: decrease prominence of GOROOT_BOOTSTRAP 
Go build scripts on UNIX (make.bash, all.bash) have not required
GOROOT_BOOTSTRAP since August 2017 (CL 57753). Windows build scripts
have followed suit since CL 96455. Most people building Go will have
a Go toolchain in their PATH and will not need to specify a different
toolchain.

This CL removes the GOROOT_BOOTSTRAP mention from the contribution guide
(it was there for Windows only, but it's not required anymore). The guide
is meant to be light and clear for beginners and is not supposed to be
a reference, so there's not need to keep mentioning GOROOT_BOOTSTRAP.

Also update install-source.html to reflect the current status quo,
where using the PATH is probably the first and most used default, and
GOROOT_BOOTSTRAP is just an option.

Change-Id: Iab453e61b0c749c256aaaf81ea9b2ae58822cb89
Reviewed-on: https://go-review.googlesource.com/c/go/+/224717
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
2020-03-28 20:43:51 +00:00

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<!--{
"Title": "Installing Go from source",
"Path": "/doc/install/source"
}-->
<h2 id="introduction">Introduction</h2>
<p>
Go is an open source project, distributed under a
<a href="/LICENSE">BSD-style license</a>.
This document explains how to check out the sources,
build them on your own machine, and run them.
</p>
<p>
Most users don't need to do this, and will instead install
from precompiled binary packages as described in
<a href="/doc/install">Getting Started</a>,
a much simpler process.
If you want to help develop what goes into those precompiled
packages, though, read on.
</p>
<div class="detail">
<p>
There are two official Go compiler toolchains.
This document focuses on the <code>gc</code> Go
compiler and tools.
For information on how to work on <code>gccgo</code>, a more traditional
compiler using the GCC back end, see
<a href="/doc/install/gccgo">Setting up and using gccgo</a>.
</p>
<p>
The Go compilers support twelve instruction sets:
<dl>
<dt>
<code>amd64</code>, <code>386</code>
</dt>
<dd>
The <code>x86</code> instruction set, 64- and 32-bit.
</dd>
<dt>
<code>arm64</code>, <code>arm</code>
</dt>
<dd>
The <code>ARM</code> instruction set, 64-bit (<code>AArch64</code>) and 32-bit.
</dd>
<dt>
<code>ppc64</code>, <code>ppc64le</code>
</dt>
<dd>
The 64-bit PowerPC instruction set, big- and little-endian.
</dd>
<dt>
<code>s390x</code>
</dt>
<dd>
The IBM z/Architecture.
</dd>
<dt>
<code>mips64</code>, <code>mips64le</code>, <code>mips</code>, <code>mipsle</code>
</dt>
<dd>
The <code>MIPS</code> instruction set, big- and little-endian, 64- and 32-bit.
</dd>
<dt>
<code>wasm</code>
</dt>
<dd>
<a href="https://webassembly.org">WebAssembly</a>.
</dd>
</dl>
</p>
<p>
The compilers can target the AIX, Android, DragonFly BSD, FreeBSD,
Illumos, Linux, macOS/iOS (Darwin), NetBSD, OpenBSD, Plan 9, Solaris,
and Windows operating systems (although not all operating systems
support all architectures).
</p>
<p>
A list of ports which are considered "first class" is available at the
<a href="/wiki/PortingPolicy#first-class-ports">first class ports</a>
wiki page.
</p>
<p>
The full set of supported combinations is listed in the
discussion of <a href="#environment">environment variables</a> below.
</p>
<p>
See the main installation page for the <a href="/doc/install#requirements">overall system requirements</a>.
The following additional constraints apply to systems that can be built only from source:
</p>
<ul>
<li>For Linux on PowerPC 64-bit, the minimum supported kernel version is 2.6.37, meaning that
Go does not support CentOS 6 on these systems.
</li>
</ul>
</div>
<h2 id="go14">Install Go compiler binaries for bootstrap</h2>
<p>
The Go toolchain is written in Go. To build it, you need a Go compiler installed.
The scripts that do the initial build of the tools look for a "go" command
in <code>$PATH</code>, so as long as you have Go installed in your
system and configured in your <code>$PATH</code>, you are ready to build Go
from source.
Or if you prefer you can set <code>$GOROOT_BOOTSTRAP</code> to the
root of a Go installation to use to build the new Go toolchain;
<code>$GOROOT_BOOTSTRAP/bin/go</code> should be the go command to use.</p>
<h3 id="bootstrapFromBinaryRelease">Bootstrap toolchain from binary release</h3>
<p>
To use a binary release as a bootstrap toolchain, see
<a href="/dl/">the downloads page</a> or use any other
packaged Go distribution.
</p>
<h3 id="bootstrapFromSource">Bootstrap toolchain from source</h3>
<p>
To build a bootstrap toolchain from source, use
either the git branch <code>release-branch.go1.4</code> or
<a href="https://dl.google.com/go/go1.4-bootstrap-20171003.tar.gz">go1.4-bootstrap-20171003.tar.gz</a>,
which contains the Go 1.4 source code plus accumulated fixes
to keep the tools running on newer operating systems.
(Go 1.4 was the last distribution in which the toolchain was written in C.)
After unpacking the Go 1.4 source, <code>cd</code> to
the <code>src</code> subdirectory, set <code>CGO_ENABLED=0</code> in
the environment, and run <code>make.bash</code> (or,
on Windows, <code>make.bat</code>).
</p>
<p>
Once the Go 1.4 source has been unpacked into your GOROOT_BOOTSTRAP directory,
you must keep this git clone instance checked out to branch
<code>release-branch.go1.4</code>. Specifically, do not attempt to reuse
this git clone in the later step named "Fetch the repository." The go1.4
bootstrap toolchain <b>must be able</b> to properly traverse the go1.4 sources
that it assumes are present under this repository root.
</p>
<h3 id="bootstrapFromCrosscompiledSource">Bootstrap toolchain from cross-compiled source</h3>
<p>
To cross-compile a bootstrap toolchain from source, which is
necessary on systems Go 1.4 did not target (for
example, <code>linux/ppc64le</code>), install Go on a different system
and run <a href="/src/bootstrap.bash">bootstrap.bash</a>.
</p>
<p>
When run as (for example)
</p>
<pre>
$ GOOS=linux GOARCH=ppc64 ./bootstrap.bash
</pre>
<p>
<code>bootstrap.bash</code> cross-compiles a toolchain for that <code>GOOS/GOARCH</code>
combination, leaving the resulting tree in <code>../../go-${GOOS}-${GOARCH}-bootstrap</code>.
That tree can be copied to a machine of the given target type
and used as <code>GOROOT_BOOTSTRAP</code> to bootstrap a local build.
</p>
<h3 id="bootstrapFromGccgo">Bootstrap toolchain using gccgo</h3>
<p>
To use gccgo as the bootstrap toolchain, you need to arrange
for <code>$GOROOT_BOOTSTRAP/bin/go</code> to be the go tool that comes
as part of gccgo 5. For example on Ubuntu Vivid:
</p>
<pre>
$ sudo apt-get install gccgo-5
$ sudo update-alternatives --set go /usr/bin/go-5
$ GOROOT_BOOTSTRAP=/usr ./make.bash
</pre>
<h2 id="git">Install Git, if needed</h2>
<p>
To perform the next step you must have Git installed. (Check that you
have a <code>git</code> command before proceeding.)
</p>
<p>
If you do not have a working Git installation,
follow the instructions on the
<a href="https://git-scm.com/downloads">Git downloads</a> page.
</p>
<h2 id="ccompiler">(Optional) Install a C compiler</h2>
<p>
To build a Go installation
with <code><a href="/cmd/cgo">cgo</a></code> support, which permits Go
programs to import C libraries, a C compiler such as <code>gcc</code>
or <code>clang</code> must be installed first. Do this using whatever
installation method is standard on the system.
</p>
<p>
To build without <code>cgo</code>, set the environment variable
<code>CGO_ENABLED=0</code> before running <code>all.bash</code> or
<code>make.bash</code>.
</p>
<h2 id="fetch">Fetch the repository</h2>
<p>Change to the directory where you intend to install Go, and make sure
the <code>goroot</code> directory does not exist. Then clone the repository
and check out the latest release tag (<code class="versionTag">go1.12</code>,
for example):</p>
<pre>
$ git clone https://go.googlesource.com/go goroot
$ cd goroot
$ git checkout <span class="versionTag"><i>&lt;tag&gt;</i></span>
</pre>
<p class="whereTag">
Where <code>&lt;tag&gt;</code> is the version string of the release.
</p>
<p>Go will be installed in the directory where it is checked out. For example,
if Go is checked out in <code>$HOME/goroot</code>, executables will be installed
in <code>$HOME/goroot/bin</code>. The directory may have any name, but note
that if Go is checked out in <code>$HOME/go</code>, it will conflict with
the default location of <code>$GOPATH</code>.
See <a href="#gopath"><code>GOPATH</code></a> below.</p>
<p>
Reminder: If you opted to also compile the bootstrap binaries from source (in an
earlier section), you still need to <code>git clone</code> again at this point
(to checkout the latest <code>&lt;tag&gt;</code>), because you must keep your
go1.4 repository distinct.
</p>
<h2 id="head">(Optional) Switch to the master branch</h2>
<p>If you intend to modify the go source code, and
<a href="/doc/contribute.html">contribute your changes</a>
to the project, then move your repository
off the release branch, and onto the master (development) branch.
Otherwise, skip this step.</p>
<pre>
$ git checkout master
</pre>
<h2 id="install">Install Go</h2>
<p>
To build the Go distribution, run
</p>
<pre>
$ cd src
$ ./all.bash
</pre>
<p>
(To build under Windows use <code>all.bat</code>.)
</p>
<p>
If all goes well, it will finish by printing output like:
</p>
<pre>
ALL TESTS PASSED
---
Installed Go for linux/amd64 in /home/you/go.
Installed commands in /home/you/go/bin.
*** You need to add /home/you/go/bin to your $PATH. ***
</pre>
<p>
where the details on the last few lines reflect the operating system,
architecture, and root directory used during the install.
</p>
<div class="detail">
<p>
For more information about ways to control the build, see the discussion of
<a href="#environment">environment variables</a> below.
<code>all.bash</code> (or <code>all.bat</code>) runs important tests for Go,
which can take more time than simply building Go. If you do not want to run
the test suite use <code>make.bash</code> (or <code>make.bat</code>)
instead.
</p>
</div>
<h2 id="testing">Testing your installation</h2>
<p>
Check that Go is installed correctly by building a simple program.
</p>
<p>
Create a file named <code>hello.go</code> and put the following program in it:
</p>
<pre>
package main
import "fmt"
func main() {
fmt.Printf("hello, world\n")
}
</pre>
<p>
Then run it with the <code>go</code> tool:
</p>
<pre>
$ go run hello.go
hello, world
</pre>
<p>
If you see the "hello, world" message then Go is installed correctly.
</p>
<h2 id="gopath">Set up your work environment</h2>
<p>
You're almost done.
You just need to do a little more setup.
</p>
<p>
<a href="/doc/code.html" class="download" id="start">
<span class="big">How to Write Go Code</span>
<span class="desc">Learn how to set up and use the Go tools</span>
</a>
</p>
<p>
The <a href="/doc/code.html">How to Write Go Code</a> document
provides <b>essential setup instructions</b> for using the Go tools.
</p>
<h2 id="tools">Install additional tools</h2>
<p>
The source code for several Go tools (including <a href="/cmd/godoc/">godoc</a>)
is kept in <a href="https://golang.org/x/tools">the go.tools repository</a>.
To install one of the tools (<code>godoc</code> in this case):
</p>
<pre>
$ go get golang.org/x/tools/cmd/godoc
</pre>
<p>
To install these tools, the <code>go</code> <code>get</code> command requires
that <a href="#git">Git</a> be installed locally.
</p>
<p>
You must also have a workspace (<code>GOPATH</code>) set up;
see <a href="/doc/code.html">How to Write Go Code</a> for the details.
</p>
<h2 id="community">Community resources</h2>
<p>
The usual community resources such as
<code>#go-nuts</code> on the <a href="https://freenode.net/">Freenode</a> IRC server
and the
<a href="//groups.google.com/group/golang-nuts">Go Nuts</a>
mailing list have active developers that can help you with problems
with your installation or your development work.
For those who wish to keep up to date,
there is another mailing list, <a href="//groups.google.com/group/golang-checkins">golang-checkins</a>,
that receives a message summarizing each checkin to the Go repository.
</p>
<p>
Bugs can be reported using the <a href="//golang.org/issue/new">Go issue tracker</a>.
</p>
<h2 id="releases">Keeping up with releases</h2>
<p>
New releases are announced on the
<a href="//groups.google.com/group/golang-announce">golang-announce</a>
mailing list.
Each announcement mentions the latest release tag, for instance,
<code class="versionTag">go1.9</code>.
</p>
<p>
To update an existing tree to the latest release, you can run:
</p>
<pre>
$ cd go/src
$ git fetch
$ git checkout <span class="versionTag"><i>&lt;tag&gt;</i></psan>
$ ./all.bash
</pre>
<p class="whereTag">
Where <code>&lt;tag&gt;</code> is the version string of the release.
</p>
<h2 id="environment">Optional environment variables</h2>
<p>
The Go compilation environment can be customized by environment variables.
<i>None is required by the build</i>, but you may wish to set some
to override the defaults.
</p>
<ul>
<li><code>$GOROOT</code>
<p>
The root of the Go tree, often <code>$HOME/go1.X</code>.
Its value is built into the tree when it is compiled, and
defaults to the parent of the directory where <code>all.bash</code> was run.
There is no need to set this unless you want to switch between multiple
local copies of the repository.
</p>
</li>
<li><code>$GOROOT_FINAL</code>
<p>
The value assumed by installed binaries and scripts when
<code>$GOROOT</code> is not set explicitly.
It defaults to the value of <code>$GOROOT</code>.
If you want to build the Go tree in one location
but move it elsewhere after the build, set
<code>$GOROOT_FINAL</code> to the eventual location.
</p>
</li>
<li id="gopath"><code>$GOPATH</code>
<p>
The directory where Go projects outside the Go distribution are typically
checked out. For example, <code>golang.org/x/tools</code> might be checked out
to <code>$GOPATH/src/golang.org/x/tools</code>. Executables outside the
Go distribution are installed in <code>$GOPATH/bin</code> (or
<code>$GOBIN</code>, if set). Modules are downloaded and cached in
<code>$GOPATH/pkg/mod</code>.
</p>
<p>The default location of <code>$GOPATH</code> is <code>$HOME/go</code>,
and it's not usually necessary to set <code>GOPATH</code> explicitly. However,
if you have checked out the Go distribution to <code>$HOME/go</code>,
you must set <code>GOPATH</code> to another location to avoid conflicts.
</p>
</li>
<li><code>$GOBIN</code>
<p>
The directory where executables outside the Go distribution are installed
using the <a href="/cmd/go">go command</a>. For example,
<code>go get golang.org/x/tools/cmd/godoc</code> downloads, builds, and
installs <code>$GOBIN/godoc</code>. By default, <code>$GOBIN</code> is
<code>$GOPATH/bin</code> (or <code>$HOME/go/bin</code> if <code>GOPATH</code>
is not set). After installing, you will want to add this directory to
your <code>$PATH</code> so you can use installed tools.
</p>
<p>
Note that the Go distribution's executables are installed in
<code>$GOROOT/bin</code> (for executables invoked by people) or
<code>$GOTOOLDIR</code> (for executables invoked by the go command;
defaults to <code>$GOROOT/pkg/$GOOS_GOARCH</code>) instead of
<code>$GOBIN</code>.
</p>
</li>
<li><code>$GOOS</code> and <code>$GOARCH</code>
<p>
The name of the target operating system and compilation architecture.
These default to the values of <code>$GOHOSTOS</code> and
<code>$GOHOSTARCH</code> respectively (described below).
</li>
<p>
Choices for <code>$GOOS</code> are
<code>android</code>, <code>darwin</code> (macOS 10.11 and above and iOS),
<code>dragonfly</code>, <code>freebsd</code>, <code>illumos</code>, <code>js</code>,
<code>linux</code>, <code>netbsd</code>, <code>openbsd</code>,
<code>plan9</code>, <code>solaris</code> and <code>windows</code>.
</p>
<p>
Choices for <code>$GOARCH</code> are
<code>amd64</code> (64-bit x86, the most mature port),
<code>386</code> (32-bit x86), <code>arm</code> (32-bit ARM), <code>arm64</code> (64-bit ARM),
<code>ppc64le</code> (PowerPC 64-bit, little-endian), <code>ppc64</code> (PowerPC 64-bit, big-endian),
<code>mips64le</code> (MIPS 64-bit, little-endian), <code>mips64</code> (MIPS 64-bit, big-endian),
<code>mipsle</code> (MIPS 32-bit, little-endian), <code>mips</code> (MIPS 32-bit, big-endian),
<code>s390x</code> (IBM System z 64-bit, big-endian), and
<code>wasm</code> (WebAssembly 32-bit).
</p>
<p>
The valid combinations of <code>$GOOS</code> and <code>$GOARCH</code> are:
<table cellpadding="0">
<tr>
<th width="50"></th><th align="left" width="100"><code>$GOOS</code></th> <th align="left" width="100"><code>$GOARCH</code></th>
</tr>
<tr>
<td></td><td><code>aix</code></td> <td><code>ppc64</code></td>
</tr>
<tr>
<td></td><td><code>android</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>android</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>android</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>android</code></td> <td><code>arm64</code></td>
</tr>
<tr>
<td></td><td><code>darwin</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>darwin</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>darwin</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>darwin</code></td> <td><code>arm64</code></td>
</tr>
<tr>
<td></td><td><code>dragonfly</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>freebsd</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>freebsd</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>freebsd</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>illumos</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>js</code></td> <td><code>wasm</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>arm64</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>ppc64</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>ppc64le</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>mips</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>mipsle</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>mips64</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>mips64le</code></td>
</tr>
<tr>
<td></td><td><code>linux</code></td> <td><code>s390x</code></td>
</tr>
<tr>
<td></td><td><code>netbsd</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>netbsd</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>netbsd</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>openbsd</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>openbsd</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>openbsd</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>openbsd</code></td> <td><code>arm64</code></td>
</tr>
<tr>
<td></td><td><code>plan9</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>plan9</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>plan9</code></td> <td><code>arm</code></td>
</tr>
<tr>
<td></td><td><code>solaris</code></td> <td><code>amd64</code></td>
</tr>
<tr>
<td></td><td><code>windows</code></td> <td><code>386</code></td>
</tr>
<tr>
<td></td><td><code>windows</code></td> <td><code>amd64</code></td>
</tr>
</table>
<br>
<li><code>$GOHOSTOS</code> and <code>$GOHOSTARCH</code>
<p>
The name of the host operating system and compilation architecture.
These default to the local system's operating system and
architecture.
</p>
</li>
<p>
Valid choices are the same as for <code>$GOOS</code> and
<code>$GOARCH</code>, listed above.
The specified values must be compatible with the local system.
For example, you should not set <code>$GOHOSTARCH</code> to
<code>arm</code> on an x86 system.
</p>
<li><code>$GO386</code> (for <code>386</code> only, default is auto-detected
if built on either <code>386</code> or <code>amd64</code>, <code>387</code> otherwise)
<p>
This controls the code generated by gc to use either the 387 floating-point unit
(set to <code>387</code>) or SSE2 instructions (set to <code>sse2</code>) for
floating point computations.
</p>
<ul>
<li><code>GO386=387</code>: use x87 for floating point operations; should support all x86 chips (Pentium MMX or later).</li>
<li><code>GO386=sse2</code>: use SSE2 for floating point operations; has better performance than 387, but only available on Pentium 4/Opteron/Athlon 64 or later.</li>
</ul>
</li>
<li><code>$GOARM</code> (for <code>arm</code> only; default is auto-detected if building
on the target processor, 6 if not)
<p>
This sets the ARM floating point co-processor architecture version the run-time
should target. If you are compiling on the target system, its value will be auto-detected.
</p>
<ul>
<li><code>GOARM=5</code>: use software floating point; when CPU doesn't have VFP co-processor</li>
<li><code>GOARM=6</code>: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)</li>
<li><code>GOARM=7</code>: use VFPv3; usually Cortex-A cores</li>
</ul>
<p>
If in doubt, leave this variable unset, and adjust it if required
when you first run the Go executable.
The <a href="//golang.org/wiki/GoArm">GoARM</a> page
on the <a href="//golang.org/wiki">Go community wiki</a>
contains further details regarding Go's ARM support.
</p>
</li>
<li><code>$GOMIPS</code> (for <code>mips</code> and <code>mipsle</code> only) <br> <code>$GOMIPS64</code> (for <code>mips64</code> and <code>mips64le</code> only)
<p>
These variables set whether to use floating point instructions. Set to "<code>hardfloat</code>" to use floating point instructions; this is the default. Set to "<code>softfloat</code>" to use soft floating point.
</p>
</li>
<li><code>$GOPPC64</code> (for <code>ppc64</code> and <code>ppc64le</code> only)
<p>
This variable sets the processor level (i.e. Instruction Set Architecture version)
for which the compiler will target. The default is <code>power8</code>.
</p>
<ul>
<li><code>GOPPC64=power8</code>: generate ISA v2.07 instructions</li>
<li><code>GOPPC64=power9</code>: generate ISA v3.00 instructions</li>
</ul>
</li>
<li><code>$GOWASM</code> (for <code>wasm</code> only)
<p>
This variable is a comma separated list of <a href="https://github.com/WebAssembly/proposals">experimental WebAssembly features</a> that the compiled WebAssembly binary is allowed to use.
The default is to use no experimental features.
</p>
<ul>
<li><code>GOWASM=satconv</code>: generate <a href="https://github.com/WebAssembly/nontrapping-float-to-int-conversions/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md">saturating (non-trapping) float-to-int conversions</a></li>
<li><code>GOWASM=signext</code>: generate <a href="https://github.com/WebAssembly/sign-extension-ops/blob/master/proposals/sign-extension-ops/Overview.md">sign-extension operators</a></li>
</ul>
</li>
</ul>
<p>
Note that <code>$GOARCH</code> and <code>$GOOS</code> identify the
<em>target</em> environment, not the environment you are running on.
In effect, you are always cross-compiling.
By architecture, we mean the kind of binaries
that the target environment can run:
an x86-64 system running a 32-bit-only operating system
must set <code>GOARCH</code> to <code>386</code>,
not <code>amd64</code>.
</p>
<p>
If you choose to override the defaults,
set these variables in your shell profile (<code>$HOME/.bashrc</code>,
<code>$HOME/.profile</code>, or equivalent). The settings might look
something like this:
</p>
<pre>
export GOARCH=amd64
export GOOS=linux
</pre>
<p>
although, to reiterate, none of these variables needs to be set to build,
install, and develop the Go tree.
</p>
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