guix.texi

derivations @code{gcc-bootstrap-0.drv}, @code{glibc-bootstrap-0.drv},
etc., at which point we have a working C tool chain.


@unnumberedsubsec Building the Build Tools

@c TODO: Add a package-level dependency graph generated from (gnu
@c packages base).

Bootstrapping is complete when we have a full tool chain that does not
depend on the pre-built bootstrap tools discussed above.  This
no-dependency requirement is verified by checking whether the files of
the final tool chain contain references to the @file{/gnu/store}
directories of the bootstrap inputs.  The process that leads to this
``final'' tool chain is described by the package definitions found in
the @code{(gnu packages base)} module.

@c See <http://lists.gnu.org/archive/html/gnu-system-discuss/2012-10/msg00000.html>.
The first tool that gets built with the bootstrap binaries is
GNU Make, which is a prerequisite for all the following packages.
From there Findutils and Diffutils get built.

Then come the first-stage Binutils and GCC, built as pseudo cross
tools---i.e., with @code{--target} equal to @code{--host}.  They are
used to build libc.  Thanks to this cross-build trick, this libc is
guaranteed not to hold any reference to the initial tool chain.

From there the final Binutils and GCC are built.  GCC uses @code{ld}
from the final Binutils, and links programs against the just-built libc.
This tool chain is used to build the other packages used by Guix and by
the GNU Build System: Guile, Bash, Coreutils, etc.

And voilà!  At this point we have the complete set of build tools that
the GNU Build System expects.  These are in the @code{%final-inputs}
variables of the @code{(gnu packages base)} module, and are implicitly
used by any package that uses @code{gnu-build-system} (@pxref{Defining
Packages}).


@unnumberedsubsec Building the Bootstrap Binaries

Because the final tool chain does not depend on the bootstrap binaries,
those rarely need to be updated.  Nevertheless, it is useful to have an
automated way to produce them, should an update occur, and this is what
the @code{(gnu packages make-bootstrap)} module provides.

The following command builds the tarballs containing the bootstrap
binaries (Guile, Binutils, GCC, libc, and a tarball containing a mixture
of Coreutils and other basic command-line tools):

@example
guix build bootstrap-tarballs
@end example

The generated tarballs are those that should be referred to in the
@code{(gnu packages bootstrap)} module mentioned at the beginning of
this section.

Still here?  Then perhaps by now you've started to wonder: when do we
reach a fixed point?  That is an interesting question!  The answer is
unknown, but if you would like to investigate further (and have
significant computational and storage resources to do so), then let us
know.

@node Porting
@section Porting to a New Platform

As discussed above, the GNU distribution is self-contained, and
self-containment is achieved by relying on pre-built ``bootstrap
binaries'' (@pxref{Bootstrapping}).  These binaries are specific to an
operating system kernel, CPU architecture, and application binary
interface (ABI).  Thus, to port the distribution to a platform that is
not yet supported, one must build those bootstrap binaries, and update
the @code{(gnu packages bootstrap)} module to use them on that platform.

Fortunately, Guix can @emph{cross compile} those bootstrap binaries.
When everything goes well, and assuming the GNU tool chain supports the
target platform, this can be as simple as running a command like this
one:

@example
guix build --target=armv5tel-linux-gnueabi bootstrap-tarballs
@end example

Once these are built, the @code{(gnu packages bootstrap)} module needs
to be updated to refer to these binaries on the target platform.  In
addition, the @code{glibc-dynamic-linker} procedure in that module must
be augmented to return the right file name for libc's dynamic linker on
that platform; likewise, @code{system->linux-architecture} in @code{(gnu
packages linux)} must be taught about the new platform.

In practice, there may be some complications.  First, it may be that the
extended GNU triplet that specifies an ABI (like the @code{eabi} suffix
above) is not recognized by all the GNU tools.  Typically, glibc
recognizes some of these, whereas GCC uses an extra @code{--with-abi}
configure flag (see @code{gcc.scm} for examples of how to handle this).
Second, some of the required packages could fail to build for that
platform.  Lastly, the generated binaries could be broken for some
reason.


@c *********************************************************************
@node Contributing
@chapter Contributing

This project is a cooperative effort, and we need your help to make it
grow!  Please get in touch with us on @email{guix-devel@@gnu.org} and
@code{#guix} on the Freenode IRC network.  We welcome ideas, bug
reports, patches, and anything that may be helpful to the project.  We
particularly welcome help on packaging (@pxref{Packaging Guidelines}).

Please see the
@url{http://git.savannah.gnu.org/cgit/guix.git/tree/HACKING,
@file{HACKING} file} that comes with the Guix source code for practical
details about contributions.


@c *********************************************************************
@node Acknowledgments
@chapter Acknowledgments

Guix is based on the Nix package manager, which was designed and
implemented by Eelco Dolstra.  Nix pioneered functional package
management, and promoted unprecedented features, such as transactional
package upgrades and rollbacks, per-user profiles, and referentially
transparent build processes.  Without this work, Guix would not exist.

The Nix-based software distributions, Nixpkgs and NixOS, have also been
an inspiration for Guix.

@c *********************************************************************
@node GNU Free Documentation License
@appendix GNU Free Documentation License

@include fdl-1.3.texi

@c *********************************************************************
@node Concept Index
@unnumbered Concept Index
@printindex cp

@node Programming Index
@unnumbered Programming Index
@syncodeindex tp fn
@syncodeindex vr fn
@printindex fn

@bye

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