Toybox: all-in-one Linux command line.

--- Getting started

You can download static binaries for various targets from:

  http://landley.net/toybox/bin

The special name "." indicates the current directory (just like ".." means
the parent directory), and you can run a program that isn't in the $PATH by
specifying a path to it, so this should work:

  wget http://landley.net/bin/toybox-x86_64
  chmod +x toybox-x86_64
  ./toybox-x86_64 echo hello world

--- Building toybox

Type "make help" for build instructions.

Usually you want something like:

  make defconfig
  CFLAGS="--static" CROSS_COMPILE=armv5l- make toybox
  PREFIX=/path/to/root/filesystem make install

The CROSS_COMPILE argument is optional, and without it builds a version of
toybox to run on the current machine. Cross compiling requires an appropriately
prefixed cross compiler toolchain, several example toolchains are available at:

  http;//landley.net/aboriginal/bin

For the "CROSS_COMPILE=armv5l-" example above, download
cross-compiler-armv5l.tar.bz2, extract it, and add its "bin" subdirectory to
your $PATH. (And yes, the trailing - is significant, because the prefix
includes a dash.)

For more about cross compiling, see:

  http://landley.net/writing/docs/cross-compiling.html
  http://landley.net/aboriginal/architectures.html

--- Using toybox

The toybox build produces a multicall binary, a "swiss-army-knife" program
that acts differently depending on the name it was called by (cp, mv, cat...).
Installing toybox adds symlinks for each command name to the $PATH.

The special "toybox" command treats its first argument as the command to run.
With no arguments, it lists available commands. This allows you to use toybox
without installing it. This is the only command that can have an arbitrary
suffix (hence "toybox-armv5l").

The "help" command provides information about each command (ala "help cat").

--- Configuring toybox

It works like the Linux kernel: allnoconfig, defconfig, and menuconfig edit
a ".config" file that selects which features to include in the resulting
binary.

The maximum sane configuration is "make defconfig": allyesconfig isn't
recommended for toybox because it enables unfinished commands and debug code.

--- Creating a Toybox-based Linux system

Toybox is not a complete operating system, it's a program that runs under
an operating system. Booting a simple system to a shell prompt requires
three packages: an operating system kernel (Linux) to drive the hardware,
a program for the system to run (toybox), and a C library to tie them
together (toybox has been tested with musl, uClibc, and glibc, on Android
systems musl is recommended).</p>

<p>The C library is part of a "toolchain", which is an integrated suite
of compiler, assembler, and linker, plus the standard headers and libraries
necessary to build C programs.</p>


 Static linking (with the --static option)
copies the shared library contents into the program, resulting in
larger but more portable programs. Dynamically linked programs (the default)
Otherwise, the
"dynamically" linked programs require the
library to be present on the target system ("man ldd" and "man ld.so" for
details) statically linked programs do not.</p>

Toybox is not a kernel, it needs Linux to drive the hardware.

An example toybox-based system is Aboriginal Linux:

  http://landley.net/aboriginal