manual/getting started: rework 'Using Buildroot' section

== Using Buildroot

*Important*: you can and should *build everything as a normal user*. There

is no need to be root to configure and use Buildroot. By running all

commands as a regular user, you protect your system against packages

behaving badly during compilation and installation.

The first step when using Buildroot is to create a configuration.

Buildroot has a nice configuration tool similar to the one you can

find in the http://www.kernel.org/[Linux kernel] or in

http://www.busybox.net/[BusyBox]. Note that you can *and should build

everything as a normal user*. There is no need to be root to configure

and use Buildroot. The first step is to run the configuration

assistant:

http://www.busybox.net/[BusyBox].

From the buildroot directory, run

--------------------

 $ make menuconfig

--------------------

or

for the original curses-based configurator, or

--------------------

 $ make nconfig

--------------------

to run the old or new curses-based configurator, or

for the new curses-based configurator, or

--------------------

 $ make xconfig

--------------------

or

for the Qt-based configurator, or

--------------------

 $ make gconfig

--------------------

to run the Qt or GTK-based configurators.

for the GTK-based configurator.

All of these "make" commands will need to build a configuration

utility (including the interface), so you may need to install

"development" packages for relevant libraries used by the

configuration utilities. Check xref:requirement[] to know what

Buildroot needs, and specifically the xref:requirement-optional[optional requirements]

configuration utilities. Refer to xref:requirement[] for more details,

specifically the xref:requirement-optional[optional requirements]

to get the dependencies of your favorite interface.

For each menu entry in the configuration tool, you can find associated

help that describes the purpose of the entry.

Once everything is configured, the configuration tool generates a

+.config+ file that contains the description of your

configuration. It will be used by the Makefiles to do what's needed.

+.config+ file that contains the entire configuration. This file will be

read by the top-level Makefile.

Let's go:

To start the build process, simply run:

--------------------

 $ make

--------------------

You *should never* use +make -jN+ with Buildroot: it does not support

'top-level parallel make'. Instead, use the +BR2_JLEVEL+ option to

tell Buildroot to run each package compilation with +make -jN+.

You *should never* use +make -jN+ with Buildroot: top-level parallel

make is currently not supported. Instead, use the +BR2_JLEVEL+ option

to tell Buildroot to run the compilation of each individual package

with +make -jN+.

The `make` command will generally perform the following steps:

* download source files (as required);

* configure, build and install the cross-compiling toolchain using the

  appropriate toolchain backend, or simply import an external toolchain;

* build/install selected target packages;

* configure, build and install the cross-compilation toolchain, or

  simply import an external toolchain;

* configure, build and install selected target packages;

* build a kernel image, if selected;

* build a bootloader image, if selected;

* create a root filesystem in selected formats.

This directory contains several subdirectories:

* +images/+ where all the images (kernel image, bootloader and root

  filesystem images) are stored.

  filesystem images) are stored. These are the files you need to put

  on your target system.

* +build/+ where all the components are built

  (this includes tools needed to run Buildroot on

  the host and packages compiled for the target). The +build/+

  directory contains one subdirectory for each of these components.

* +build/+ where all the components are built (this includes tools

  needed by Buildroot on the host and packages compiled for the

  target). This directory contains one subdirectory for each of these

  components.

* +staging/+ which contains a hierarchy similar to a root filesystem

  hierarchy. This directory contains the installation of the

  hierarchy. This directory contains the headers and libraries of the

  cross-compilation toolchain and all the userspace packages selected

  for the target. However, this directory is 'not' intended to be

  the root filesystem for the target: it contains a lot of development

These commands, +make menuconfig|nconfig|gconfig|xconfig+ and +make+, are the

basic ones that allow to easily and quickly generate images fitting

your needs, with all the supports and applications you enabled.

your needs, with all the features and applications you enabled.

More details about the "make" command usage are given in

xref:make-tips[].