aboutsummaryrefslogtreecommitdiff
path: root/doc/guix.texi
blob: 60b1534ad429b4dbc0d524d59f5d984e2ec79d01 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
\input texinfo
@c -*-texinfo-*-

@c %**start of header
@setfilename guix.info
@documentencoding UTF-8
@settitle GNU Guix Reference Manual
@c %**end of header

@include version.texi
@set YEARS 2012, 2013

@dircategory Package management
@direntry
* guix: (guix).       Guix, the functional package manager.
* guix-package: (guix)Invoking guix-package
                      Managing packages with Guix.
* guix-build: (guix)Invoking guix-build
                      Building packages with Guix.
@end direntry

@titlepage
@title{GNU Guix Reference Manual}
@subtitle{Using the GNU Guix Functional Package Manager}
@author Ludovic Courtès

@page
@vskip 0pt plus 1filll
Edition @value{EDITION} @*
@value{UPDATED} @*

Copyright @copyright{} @value{YEARS} Ludovic Court@`es

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License''.
@end quotation
@end titlepage

@copying
This manual documents GNU Guix version @value{VERSION}.

Copyright @copyright{} @value{YEARS} Ludovic Courtès

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License.''
@end copying

@contents

@c *********************************************************************
@node Top
@top GNU Guix

This document describes GNU Guix version @value{VERSION}, a functional
package management tool written for the GNU system.

@quotation
Copyright @copyright{} @value{YEARS} Ludovic Courtès

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License.''
@end quotation

@menu
* Introduction::                What is Guix about?
* Installation::                Installing Guix.
* Package Management::          Package installation, upgrade, etc.
* Programming Interface::       Using Guix in Scheme.
* Utilities::                   Package management commands.

* Acknowledgments::             Thanks!
* GNU Free Documentation License::  The license of this manual.
* Concept Index::               Concepts.
* Function Index::              Functions.
@end menu

@c *********************************************************************
@node Introduction
@chapter Introduction

GNU Guix@footnote{``Guix'' is pronounced like ``geeks'', or ``ɡiːks''
using the international phonetic alphabet (IPA).} is a functional
package management tool for the GNU system.  Package management consists
in all the activities that relate to building packages from source,
honoring the build-time and run-time dependencies on packages,
installing packages in user environments, upgrading installed packages
to new versions or rolling back to a previous set, removing unused
software packages, etc.

@cindex functional package management
The term @dfn{functional} refers to a specific package management
discipline.  In Guix, the package build and installation process is seen
as a function, in the mathematical sense: that function takes inputs,
such as build scripts, a compiler, and libraries depended on, and
returns the installed package.  As a pure function, its result depends
solely on its inputs---for instance, it cannot refer to software or
scripts that were not explicitly passed as inputs.  A build function
always produces the same result when passed a given set of inputs.  Last
but not least, a build function cannot alter the system's environment in
any way; for instance, it cannot create, modify, or delete files outside
of its build and installation directories.  This is achieved by running
build processes in dedicated ``chroots'', where only their explicit
inputs are visible.

@cindex package store
The result of package build functions is @dfn{cached} in the file
system, in a special directory called the @dfn{package store}.  In
practice, each package is installed in a directory of its own, in the
store---by default under @file{/nix/store}.  The directory name contains
a hash of all the inputs used to build that package; thus, changing an
input yields a different directory name.

This approach is the foundation of Guix's salient features: support for
transactional package upgrades and rollback, per-user installation, and
garbage collection of packages (@pxref{Features}).

Guix has a command-line interface allowing users to build, install,
upgrade, and remove packages, as well as a Scheme programming interface.
The remainder of this manual describes them.

@c *********************************************************************
@node Installation
@chapter Installation

This section describes the software requirements of Guix, as well as how
to install it and get ready to use it.

@menu
* Requirements::                Software needed to build and run Guix.
* Setting Up the Daemon::       Preparing the build daemon's environment.
* Invoking guix-daemon::        Running the build daemon.
@end menu

@node Requirements
@section Requirements

GNU Guix depends on the following packages:

@itemize
@item @url{http://gnu.org/software/guile/, GNU Guile 2.0.x};
@item @url{http://gnupg.org/, GNU libgcrypt}
@end itemize

Unless @code{--disable-daemon} was passed to @command{configure}, the
following packages are also needed:

@itemize
@item @url{http://sqlite.org, SQLite 3}
@item @url{http://www.bzip.org, libbz2}
@item @url{http://gcc.gnu.org, GCC's g++}
@end itemize

When a working installation of the Nix package manager is available, you
can instead configure Guix with @code{--disable-daemon}.  In that case,
@url{http://nixos.org/nix/, Nix} replaces the three dependencies above.

@node Setting Up the Daemon
@section Setting Up the Daemon

@cindex daemon
Operations such as building a package or running the garbage collector
are all performed by a specialized process, the @dfn{Guix daemon}, on
behalf of clients.  Only the daemon may access the store and its
associated database.  Thus, any operation that manipulates the store
goes through the daemon.  For instance, command-line tools such as
@command{guix-package} and @command{guix-build} communicate with the
daemon (@i{via} remote procedure calls) to instruct it what to do.

In a standard multi-user setup, Guix and its daemon---the
@command{guix-daemon} program---are installed by the system
administrator; @file{/nix/store} is owned by @code{root} and
@command{guix-daemon} runs as @code{root}.  Unprivileged users may use
Guix tools to build packages or otherwise access the store, and the
daemon will do it on their behalf, ensuring that the store is kept in a
consistent state, and allowing built packages to be shared among users.

@cindex build users
When @command{guix-daemon} runs as @code{root}, you may not want package
build processes themselves to run as @code{root} too, for obvious
security reasons.  To avoid that, a special pool of @dfn{build users}
should be created for use by build processes started by the daemon.
These build users need not have a shell and a home directory: they will
just be used when the daemon drops @code{root} privileges in build
processes.  Having several such users allows the daemon to launch
distinct build processes under separate UIDs, which guarantees that they
do not interfere with each other---an essential feature since builds are
regarded as pure functions (@pxref{Introduction}).

On a GNU/Linux system, a build user pool may be created like this (using
Bash syntax and the @code{shadow} commands):

@example
# groupadd guix-builder
# for i in `seq 1 10`;
  do
    useradd -g guix-builder -d /var/empty -s `which nologin` \
            -m "Guix build user $i" guix-builder$i;
  done
@end example

@noindent
The @code{guix-daemon} program may then be run as @code{root} with:

@example
# guix-daemon --build-users-group=guix-builder
@end example

Guix may also be used in a single-user setup, with @command{guix-daemon}
running as a unprivileged user.  However, to maximize non-interference
of build processes, the daemon still needs to perform certain operations
that are restricted to @code{root} on GNU/Linux: it should be able to
run build processes in a chroot, and to run them under different UIDs.
To that end, the @command{nix-setuid-helper} program is provided; it is
a small C program (less than 300 lines) that, if it is made setuid
@code{root}, can be executed by the daemon to perform these operations
on its behalf.  The @code{root}-owned @file{/etc/nix-setuid.conf} file
is read by @command{nix-setuid-helper}; it should contain exactly two
words: the user name under which the authorized @command{guix-daemon}
runs, and the name of the build users group.

If you are installing Guix as an unprivileged user and do not have the
ability to make @file{nix-setuid-helper} setuid-@code{root}, it is still
possible to run @command{guix-daemon}.  However, build processes will
not be isolated from one another, and not from the rest of the system.
Thus, build processes may interfere with each other, and may access
programs, libraries, and other files available on the system---making it
much harder to view them as @emph{pure} functions.

@node Invoking guix-daemon
@section Invoking @command{guix-daemon}

The @command{guix-daemon} program implements all the functionality to
access the store.  This includes launching build processes, running the
garbage collector, querying the availability of a build result, etc.  It
is normally run as @code{root} like this:

@example
# guix-daemon --build-users-group=guix-builder
@end example

@noindent
For details on how to set it up, @ref{Setting Up the Daemon}.

By default, @command{guix-daemon} launches build processes under
different UIDs, taken from the build group specified with
@code{--build-users-group}.  In addition, each build process is run in a
chroot environment that only contains the subset of the store that the
build process depends on, as specified by its derivation
(@pxref{Programming Interface, derivation}), plus a set of specific
system directories.  By default, the latter contains @file{/dev} and
@file{/dev/pts}.

The following command-line options are supported:

@table @code
@item --build-users-group=@var{group}
Take users from @var{group} to run build processes (@pxref{Setting Up
the Daemon, build users}).

@item --cache-failures
Cache build failures.  By default, only successful builds are cached.

@item --cores=@var{n}
@itemx -c @var{n}
Use @var{n} CPU cores to build each derivation; @code{0} means as many
as available.

The default value is @code{1}, but it may be overridden by clients, such
as the @code{--cores} option of @command{guix-build} (@pxref{Invoking
guix-build}).

The effect is to define the @code{NIX_BUILD_CORES} environment variable
in the build process, which can then use it to exploit internal
parallelism---for instance, by running @code{make -j$NIX_BUILD_CORES}.

@item --max-jobs=@var{n}
@itemx -M @var{n}
Allow at most @var{n} build jobs in parallel.  The default value is
@code{1}.

@item --debug
Produce debugging output.

This is useful to debug daemon start-up issues, but then it may be
overridden by clients, for example the @code{--verbosity} option of
@command{guix-build} (@pxref{Invoking guix-build}).

@item --chroot-directory=@var{dir}
Add @var{dir} to the build chroot.

Doing this may change the result of build processes---for instance if
they use optional dependencies found in @var{dir} when it is available,
and not otherwise.  For that reason, it is not recommended to do so.
Instead, make sure that each derivation declares all the inputs that it
needs.

@item --disable-chroot
Disable chroot builds.

Using this option is not recommended since, again, it would allow build
processes to gain access to undeclared dependencies.

@item --disable-log-compression
Disable compression of the build logs.

@item --disable-store-optimization
Disable automatic file ``deduplication'' in the store.

@item --impersonate-linux-2.6
On Linux-based systems, impersonate Linux 2.6.  This means that the
kernel's @code{uname} system call will report 2.6 as the release number.

This might be helpful to build programs that (usually wrongfully) depend
on the kernel version number.

@item --lose-logs
Do not keep build logs.  By default they are kept under
@code{@var{localstatedir}/nix/log}.

@item --system=@var{system}
Assume @var{system} as the current system type.  By default it is the
architecture/kernel pair found at configure time, such as
@code{x86_64-linux}.
@end table


@c *********************************************************************
@node Package Management
@chapter Package Management

The purpose of GNU Guix is to allow users to easily install, upgrade, and
remove software packages, without having to know about their build
procedure or dependencies.  Guix also goes beyond this obvious set of
features.

This chapter describes the main features of Guix, as well as the package
management tools it provides.

@menu
* Features::                    How Guix will make your life brighter.
* Invoking guix-package::       Package installation, removal, etc.
* Invoking guix-gc::            Running the garbage collector.
@end menu

@node Features
@section Features

When using Guix, each package ends up in the @dfn{package store}, in its
own directory---something that resembles
@file{/nix/store/xxx-package-1.2}, where @code{xxx} is a base32 string.

Instead of referring to these directories, users have their own
@dfn{profile}, which points to the packages that they actually want to
use.  That profile is normally stored in @code{$HOME/.guix-profile}, and
each user has its own profile.

For example, if @code{alice} installed GCC 4.7.2, then
@file{/home/alice/.guix-profile/bin/gcc} points to
@file{/nix/store/xxx-gcc-4.7.2/bin/gcc}; on the same machine, @code{bob}
may have installed GCC 4.8.0, in which case its profile refers to these
particular package installation.  Both coexist, without any
interference.

The @command{guix-package} command is the central tool to manage
packages.  It operates on those per-user profiles, and can be used
@emph{with normal user privileges}.

The command provides the obvious install, remove, and upgrade
operations.  Each invocation is actually a @emph{transaction}: either
the specified operation succeeds, or nothing happens.  Thus, if the
@command{guix-package} processed is terminated during the transaction,
or if a power outage occurs during the transaction, then the user's
profile remains in its previous state, and remains usable.

In addition, any package transaction may be @emph{rolled back}.  So, if,
for example, an upgrade installs a new version of a package that turns
out to have a serious bug, users may roll back to the previous instance
of their profile, which was known to work well.

All those packages in the package store may be @emph{garbage-collected}.
Guix can determine which packages are still referenced by the user
profiles, and remove those that are provably no longer referenced
(@pxref{Invoking guix-gc}).  Users may also explicitly remove old
generations of their profile so that the packages they refer to can be
collected.

Finally, Guix takes a @dfn{purely functional} approach to package
management, as described in the introduction (@pxref{Introduction}).
Each @file{/nix/store} package directory name contains a hash of all the
inputs that were used to build that package---compiler, libraries, build
scripts, etc.  This direct correspondence allows users to make sure a
given package installation matches the current state of their
distribution.

This foundation allows Guix to support @dfn{transparent binary/source
deployment}.  When a pre-built binary for a @file{/nix/store} path is
available from an external source, Guix just downloads it; otherwise, it
builds the package from source, locally.

@node Invoking guix-package
@section Invoking @command{guix-package}

The @command{guix-package} command is the tool that allows users to
install, upgrade, and remove packages, as well as rolling back to
previous configurations.  It operates only on the user's own profile,
and works with normal user privileges (@pxref{Features}).  Its syntax
is:

@example
guix-package @var{options}
@end example

Primarily, @var{options} specifies the operations to be performed during
the transaction.  Upon completion, a new profile is created, but
previous generations of the profile remain available, should the user
want to roll back.

For each user, a symlink to the user's default profile is automatically
created in @file{$HOME/.guix-profile}.  This symlink always point to the
current generation of the user's default profile.  Thus, users can add
@file{$HOME/.guix-profile/bin} to their @code{PATH} environment
variable, and so on.

@table @code

@item --install=@var{package}
@itemx -i @var{package}
Install @var{package}.

@var{package} may specify either a simple package name, such as
@code{guile}, or a package name followed by a hyphen and version number,
such as @code{guile-1.8.8}.  In addition, @var{package} may contain a
colon, followed by the name of one of the outputs of the package, as in
@code{gcc:doc} or @code{libsigsegv-2.10:lib}.

@item --remove=@var{package}
@itemx -r @var{package}
Remove @var{package}.

@item --upgrade=@var{regexp}
@itemx -u @var{regexp}
Upgrade all the installed packages matching @var{regexp}.

@item --profile=@var{profile}
@itemx -p @var{profile}
Use @var{profile} instead of the user's default profile.

@item --dry-run
@itemx -n
Show what would be done without actually doing it.

@item --verbose
Produce verbose output.  In particular, emit the environment's build log
on the standard error port.

@item --bootstrap
Use the bootstrap Guile to build the profile.  This option is only
useful to distribution developers.

@end table

In addition to these actions @command{guix-package} supports the
following options to query the current state of a profile, or the
availability of packages:

@table @option

@item --list-installed[=@var{regexp}]
@itemx -I [@var{regexp}]
List currently installed packages in the specified profile.  When
@var{regexp} is specified, list only installed packages whose name
matches @var{regexp}.

For each installed package, print the following items, separated by
tabs: the package name, its version string, the part of the package that
is installed (for instance, @code{out} for the default output,
@code{include} for its headers, etc.), and the path of this package in
the store.

@item --list-available[=@var{regexp}]
@itemx -A [@var{regexp}]
List packages currently available in the software distribution.  When
@var{regexp} is specified, list only installed packages whose name
matches @var{regexp}.

For each package, print the following items separated by tabs: its name,
its version string, the parts of the package (@code{out} for the main
files, @code{lib} for libraries and possibly headers, etc.), and the
source location of its definition.

@end table


@node Invoking guix-gc
@section Invoking @command{guix-gc}

@cindex garbage collector
Packages that are installed but not used may be @dfn{garbage-collected}.
The @command{guix-gc} command allows users to explicitly run the garbage
collector to reclaim space from the @file{/nix/store} directory.

The garbage collector has a set of known @dfn{roots}: any file under
@file{/nix/store} reachable from a root is considered @dfn{live} and
cannot be deleted; any other file is considered @dfn{dead} and may be
deleted.  The set of garbage collector roots includes default user
profiles, and may be augmented with @command{guix-build --root}, for
example (@pxref{Invoking guix-build}).

The @command{guix-gc} command has three mode of operations: it can be
used to garbage-collect any dead files (the default), to delete specific
files (the @code{--delete} option), or to print garbage-collector
information.  The available options are listed below:

@table @code
@item --collect-garbage[=@var{min}]
@itemx -C [@var{min}]
Collect garbage---i.e., unreachable @file{/nix/store} files and
sub-directories.  This is the default operation when no option is
specified.

When @var{min} is given, stop once @var{min} bytes have been collected.
@var{min} may be a number of bytes, or it may include a unit as a
suffix, such as @code{MiB} for mebibytes and @code{GB} for gigabytes.

When @var{min} is omitted, collect all the garbage.

@item --delete
@itemx -d
Attempt to delete all the store files and directories specified as
arguments.  This fails if some of the files are not in the store, or if
they are still live.

@item --list-dead
Show the list of dead files and directories still present in the
store---i.e., files and directories no longer reachable from any root.

@item --list-live
Show the list of live store files and directories.
@end table


@c *********************************************************************
@node Programming Interface
@chapter Programming Interface

GNU Guix provides several Scheme programming interfaces (APIs) to
define, build, and query packages.  The first interface allows users to
write high-level package definitions.  These definitions refer to
familiar packaging concepts, such as the name and version of a package,
its build system, and its dependencies.  These definitions can then be
turned into concrete build actions.

Build actions are performed by the Guix daemon, on behalf of users.  In a
standard setup, the daemon has write access to the store---the
@file{/nix/store} directory---whereas users do not.  The recommended
setup also has the daemon perform builds in chroots, under a specific
build users, to minimize interference with the rest of the system.

@cindex derivation
Lower-level APIs are available to interact with the daemon and the
store.  To instruct the daemon to perform a build action, users actually
provide it with a @dfn{derivation}.  A derivation is a low-level
representation of the build actions to be taken, and the environment in
which they should occur---derivations are to package definitions what
assembly is to C programs.

This chapter describes all these APIs in turn, starting from high-level
package definitions.

@menu
* Defining Packages::   Defining new packages.
* The Store::           Manipulating the package store.
* Derivations::         Low-level interface to package derivations.
@end menu

@node Defining Packages
@section Defining Packages

The high-level interface to package definitions is implemented in the
@code{(guix packages)} and @code{(guix build-system)} modules.  As an
example, the package definition, or @dfn{recipe}, for the GNU Hello
package looks like this:

@example
(define hello
  (package
    (name "hello")
    (version "2.8")
    (source (origin
             (method url-fetch)
             (uri (string-append "mirror://gnu/hello/hello-" version
                                 ".tar.gz"))
             (sha256
              (base32 "0wqd8sjmxfskrflaxywc7gqw7sfawrfvdxd9skxawzfgyy0pzdz6"))))
    (build-system gnu-build-system)
    (inputs `(("gawk" ,gawk)))
    (synopsis "GNU Hello")
    (description "Yeah...")
    (home-page "http://www.gnu.org/software/hello/")
    (license "GPLv3+")))
@end example

@noindent
Without being a Scheme expert, the reader may have guessed the meaning
of the various fields here.  This expression binds variable @var{hello}
to a @code{<package>} object, which is essentially a record
(@pxref{SRFI-9, Scheme records,, guile, GNU Guile Reference Manual}).
This package object can be inspected using procedures found in the
@code{(guix packages)} module; for instance, @code{(package-name hello)}
returns---surprise!---@code{"hello"}.

There are a few points worth noting in the above package definition:

@itemize
@item
The @code{source} field of the package is an @code{<origin>} object.
Here, the @code{url-fetch} method from @code{(guix download)} is used,
meaning that the source is a file to be downloaded over FTP or HTTP.

The @code{mirror://gnu} prefix instructs @code{url-fetch} to use one of
the GNU mirrors defined in @code{(guix download)}.

The @code{sha256} field specifies the expected SHA256 hash of the file
being downloaded.  It is mandatory, and allows Guix to check the
integrity of the file.  The @code{(base32 @dots{})} form introduces the
base32 representation of the hash.  A convenient way to obtain this
information is with the @code{guix-download} tool.

@item
@cindex GNU Build System
The @code{build-system} field is set to @var{gnu-build-system}.  The
@var{gnu-build-system} variable is defined in the @code{(guix
build-system gnu)} module, and is bound to a @code{<build-system>}
object.

Naturally, @var{gnu-build-system} represents the familiar GNU Build
System, and variants thereof (@pxref{Configuration, configuration and
makefile conventions,, standards, GNU Coding Standards}).  In a
nutshell, packages using the GNU Build System may be configured, built,
and installed with the usual @code{./configure && make && make check &&
make install} command sequence.  This is what @var{gnu-build-system}
does.

In addition, @var{gnu-build-system} ensures that the ``standard''
environment for GNU packages is available.  This includes tools such as
GCC, Coreutils, Bash, Make, Diffutils, and Patch.

@item
The @code{inputs} field specifies inputs to the build process---i.e.,
build-time or run-time dependencies of the package.  Here, we define an
input called @code{"gawk"} whose value is that of the @var{gawk}
variable; @var{gawk} is itself bound to a @code{<package>} object.

Note that GCC, Coreutils, Bash, and other essential tools do not need to
be specified as inputs here.  Instead, @var{gnu-build-system} takes care
of ensuring that they are present.

However, any other dependencies need to be specified in the
@code{inputs} field.  Any dependency not specified here will simply be
unavailable to the build process, possibly leading to a build failure.
@end itemize

There are other fields that package definitions may provide.  Of
particular interest is the @code{arguments} field.  When specified, it
must be bound to a list of additional arguments to be passed to the
build system.  For instance, the above definition could be augmented
with the following field initializer:

@example
    (arguments `(#:tests? #f
                 #:configure-flags '("--enable-silent-rules")))
@end example

@noindent
These are keyword arguments (@pxref{Optional Arguments, keyword
arguments in Guile,, guile, GNU Guile Reference Manual}).  They are
passed to @var{gnu-build-system}, which interprets them as meaning ``do
not run @code{make check}'', and ``run @file{configure} with the
@code{--enable-silent-rules} flag''.

Once a package definition is in place@footnote{Simple package
definitions like the one above may be automatically converted from the
Nixpkgs distribution using the @command{guix-import} command.}, the
package may actually be built using the @code{guix-build} command-line
tool (@pxref{Invoking guix-build}).

Behind the scenes, a derivation corresponding to the @code{<package>}
object is first computed by the @code{package-derivation} procedure.
That derivation is stored in a @code{.drv} file under @file{/nix/store}.
The build actions it prescribes may then be realized by using the
@code{build-derivations} procedure (@pxref{The Store}).

@deffn {Scheme Procedure} package-derivation @var{store} @var{package} [@var{system}]
Return the derivation of @var{package} for @var{system}.  The result is
the file name of the derivation---i.e., a @code{.drv} file under
@code{/nix/store}.

@var{package} must be a valid @code{<package>} object, and @var{system}
must be a string denoting the target system type---e.g.,
@code{"x86_64-linux"} for an x86_64 Linux-based GNU system.  @var{store}
must be a connection to the daemon, which operates on the store
(@pxref{The Store}).
@end deffn

@node The Store
@section The Store

@code{(guix store)}

@node Derivations
@section Derivations

@code{(guix derivations)}

@c *********************************************************************
@node Utilities
@chapter Utilities

@menu
* Invoking guix-build:: Building packages from the command line.
@end menu

@node Invoking guix-build
@section Invoking @command{guix-build}

The @command{guix-build} command builds packages or derivations and
their dependencies, and prints the resulting store paths.  It is mainly
useful for distribution developers.  The general syntax is:

@example
guix-build @var{options} @var{package-or-derivation}@dots{}
@end example

@var{package-or-derivation} may be either the name of a package found in
the software distribution such as @code{coreutils}, or a derivation such
as @file{/nix/store/xxx-coreutils-8.19.drv}.  Alternatively, the
@code{--expression} option may be used to specify a Scheme expression
that evaluates to a package; this is useful when disambiguation among
several same-named packages or package variants is needed.

The @var{options} may be zero or more of the following:

@table @code

@item --expression=@var{expr}
@itemx -e @var{expr}
Build the package @var{expr} evaluates to.

For example, @var{expr} may be @code{(@@ (distro packages guile)
guile-1.8)}, which unambiguously designates this specific variant of
version 1.8 of Guile.

@item --source
@itemx -S
Build the packages' source derivations, rather than the packages
themselves.

For instance, @code{guix-build -S gcc} returns something like
@file{/nix/store/xxx-gcc-4.7.2.tar.bz2}, which is GCC's source tarball.

@item --system=@var{system}
@itemx -s @var{system}
Attempt to build for @var{system}---e.g., @code{i686-linux}---instead of
the host's system type.

An example use of this is on Linux-based systems, which can emulate
different personalities.  For instance, passing
@code{--system=i686-linux} on an @code{x86_64-linux} system allows users
to build packages in a complete 32-bit environment.

@item --derivations
@itemx -d
Return the derivation paths, not the output paths, of the given
packages.

@item --keep-failed
@itemx -K
Keep the build tree of failed builds.  Thus, if a build fail, its build
tree is kept under @file{/tmp}, in a directory whose name is shown at
the end of the build log.  This is useful when debugging build issues.

@item --dry-run
@itemx -n
Do not build the derivations.

@item --no-substitutes
Build instead of resorting to pre-built substitutes.

@item --cores=@var{n}
@itemx -c @var{n}
Allow the use of up to @var{n} CPU cores for the build.  The special
value @code{0} means to use as many CPU cores as available.

@item --root=@var{file}
@itemx -r @var{file}
Make @var{file} a symlink to the result, and register it as a garbage
collector root.

@item --verbosity=@var{level}
Use the given verbosity level.  @var{level} must be an integer between 0
and 5; higher means more verbose output.  Setting a level of 4 or more
may be helpful when debugging setup issues with the build daemon.

@end table

Behind the scenes, @command{guix-build} is essentially an interface to
the @code{package-derivation} procedure of the @code{(guix packages)}
module, and to the @code{build-derivations} procedure of the @code{(guix
store)} module.


@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 Function Index
@unnumbered Function Index
@printindex fn

@bye

@c Local Variables:
@c ispell-local-dictionary: "american";
@c End: