The Standard EnvironmentThe standard build environment in the Nix Packages collection
provides an environment for building Unix packages that does a lot of
common build tasks automatically. In fact, for Unix packages that use
the standard ./configure; make; make install build
interface, you don’t need to write a build script at all; the standard
environment does everything automatically. If
stdenv doesn’t do what you need automatically, you
can easily customise or override the various build phases.Using
stdenvTo build a package with the standard environment, you use the
function stdenv.mkDerivation, instead of the
primitive built-in function derivation, e.g.
stdenv.mkDerivation {
name = "libfoo-1.2.3";
src = fetchurl {
url = http://example.org/libfoo-1.2.3.tar.bz2;
md5 = "e1ec107956b6ddcb0b8b0679367e9ac9";
};
}
(stdenv needs to be in scope, so if you write this
in a separate Nix expression from
pkgs/all-packages.nix, you need to pass it as a
function argument.) Specifying a name and a
src is the absolute minimum you need to do. Many
packages have dependencies that are not provided in the standard
environment. It’s usually sufficient to specify those dependencies in
the buildInputs attribute:
stdenv.mkDerivation {
name = "libfoo-1.2.3";
...
buildInputs = [libbar perl ncurses];
}
This attribute ensures that the bin
subdirectories of these packages appear in the PATH
environment variable during the build, that their
include subdirectories are searched by the C
compiler, and so on. (See for
details.)Often it is necessary to override or modify some aspect of the
build. To make this easier, the standard environment breaks the
package build into a number of phases, all of
which can be overridden or modified individually: unpacking the
sources, applying patches, configuring, building, and installing.
(There are some others; see .)
For instance, a package that doesn’t supply a makefile but instead has
to be compiled “manually” could be handled like this:
stdenv.mkDerivation {
name = "fnord-4.5";
...
buildPhase = ''
gcc foo.c -o foo
'';
installPhase = ''
mkdir -p $out/bin
cp foo $out/bin
'';
}
(Note the use of ''-style string literals, which
are very convenient for large multi-line script fragments because they
don’t need escaping of " and \,
and because indentation is intelligently removed.)There are many other attributes to customise the build. These
are listed in .While the standard environment provides a generic builder, you
can still supply your own build script:
stdenv.mkDerivation {
name = "libfoo-1.2.3";
...
builder = ./builder.sh;
}
where the builder can do anything it wants, but typically starts with
source $stdenv/setup
to let stdenv set up the environment (e.g., process
the buildInputs). If you want, you can still use
stdenv’s generic builder:
source $stdenv/setup
buildPhase() {
echo "... this is my custom build phase ..."
gcc foo.c -o foo
}
installPhase() {
mkdir -p $out/bin
cp foo $out/bin
}
genericBuild
Tools provided by
stdenvThe standard environment provides the following packages:
The GNU C Compiler, configured with C and C++
support.GNU coreutils (contains a few dozen standard Unix
commands).GNU findutils (contains
find).GNU diffutils (contains diff,
cmp).GNU sed.GNU grep.GNU awk.GNU tar.gzip, bzip2
and xz.GNU Make. It has been patched to provide
nested output that can be fed into the
nix-log2xml command and
log2html stylesheet to create a structured,
readable output of the build steps performed by
Make.Bash. This is the shell used for all builders in
the Nix Packages collection. Not using /bin/sh
removes a large source of portability problems.The patch
command.On Linux, stdenv also includes the
patchelf utility.AttributesVariables affecting stdenv
initialisationNIX_DEBUGIf set, stdenv will print some
debug information during the build. In particular, the
gcc and ld wrapper scripts
will print out the complete command line passed to the wrapped
tools.buildInputsA list of dependencies used by
stdenv to set up the environment for the build.
For each dependency dir, the directory
dir/bin, if it
exists, is added to the PATH environment variable.
Other environment variables are also set up via a pluggable
mechanism. For instance, if buildInputs
contains Perl, then the lib/site_perl
subdirectory of each input is added to the PERL5LIB
environment variable. See for
details.propagatedBuildInputsLike buildInputs, but these
dependencies are propagated: that is, the
dependencies listed here are added to the
buildInputs of any package that uses
this package as a dependency. So if package
Y has propagatedBuildInputs = [X], and package
Z has buildInputs = [Y], then package X will
appear in Z’s build environment automatically.Variables affecting build propertiesenableParallelBuildingIf set, stdenv will pass specific
flags to make and other build tools to enable
parallel building with up to build-cores
workers.preferLocalBuildIf set, specifies that the package is so lightweight
in terms of build operations (e.g. write a text file from a Nix string
to the store) that there's no need to look for it in binary caches --
it's faster to just build it locally. It also tells Hydra and other
facilities that this package doesn't need to be exported in binary
caches (noone would use it, after all).Special variablespassthruThis is an attribute set which can be filled with arbitrary
values. For example:
passthru = {
foo = "bar";
baz = {
value1 = 4;
value2 = 5;
};
}
Values inside it are not passed to the builder, so you can change
them without triggering a rebuild. However, they can be accessed outside of a
derivation directly, as if they were set inside a derivation itself, e.g.
hello.baz.value1. We don't specify any usage or
schema of passthru - it is meant for values that would be
useful outside the derivation in other parts of a Nix expression (e.g. in other
derivations). An example would be to convey some specific dependency of your
derivation which contains a program with plugins support. Later, others who
make derivations with plugins can use passed-through dependency to ensure that
their plugin would be binary-compatible with built program.PhasesThe generic builder has a number of phases.
Package builds are split into phases to make it easier to override
specific parts of the build (e.g., unpacking the sources or installing
the binaries). Furthermore, it allows a nicer presentation of build
logs in the Nix build farm.Each phase can be overridden in its entirety either by setting
the environment variable
namePhase to a string
containing some shell commands to be executed, or by redefining the
shell function
namePhase. The former
is convenient to override a phase from the derivation, while the
latter is convenient from a build script.Controlling
phasesThere are a number of variables that control what phases are
executed and in what order:
Variables affecting phase controlphasesSpecifies the phases. You can change the order in which
phases are executed, or add new phases, by setting this
variable. If it’s not set, the default value is used, which is
$prePhases unpackPhase patchPhase $preConfigurePhases
configurePhase $preBuildPhases buildPhase checkPhase
$preInstallPhases installPhase fixupPhase $preDistPhases
distPhase $postPhases.
Usually, if you just want to add a few phases, it’s more
convenient to set one of the variables below (such as
preInstallPhases), as you then don’t specify
all the normal phases.prePhasesAdditional phases executed before any of the default phases.preConfigurePhasesAdditional phases executed just before the configure phase.preBuildPhasesAdditional phases executed just before the build phase.preInstallPhasesAdditional phases executed just before the install phase.preFixupPhasesAdditional phases executed just before the fixup phase.preDistPhasesAdditional phases executed just before the distribution phase.postPhasesAdditional phases executed after any of the default
phases.The unpack phaseThe unpack phase is responsible for unpacking the source code of
the package. The default implementation of
unpackPhase unpacks the source files listed in
the src environment variable to the current directory.
It supports the following files by default:
Tar filesThese can optionally be compressed using
gzip (.tar.gz,
.tgz or .tar.Z),
bzip2 (.tar.bz2 or
.tbz2) or xz
(.tar.xz or
.tar.lzma).Zip filesZip files are unpacked using
unzip. However, unzip is
not in the standard environment, so you should add it to
buildInputs yourself.Directories in the Nix storeThese are simply copied to the current directory.
The hash part of the file name is stripped,
e.g. /nix/store/1wydxgby13cz...-my-sources
would be copied to
my-sources.
Additional file types can be supported by setting the
unpackCmd variable (see below).Variables controlling the unpack phasesrcs / srcThe list of source files or directories to be
unpacked or copied. One of these must be set.sourceRootAfter running unpackPhase,
the generic builder changes the current directory to the directory
created by unpacking the sources. If there are multiple source
directories, you should set sourceRoot to the
name of the intended directory.setSourceRootAlternatively to setting
sourceRoot, you can set
setSourceRoot to a shell command to be
evaluated by the unpack phase after the sources have been
unpacked. This command must set
sourceRoot.preUnpackHook executed at the start of the unpack
phase.postUnpackHook executed at the end of the unpack
phase.dontMakeSourcesWritableIf set to 1, the unpacked
sources are not made
writable. By default, they are made writable to prevent problems
with read-only sources. For example, copied store directories
would be read-only without this.unpackCmdThe unpack phase evaluates the string
$unpackCmd for any unrecognised file. The path
to the current source file is contained in the
curSrc variable.The patch phaseThe patch phase applies the list of patches defined in the
patches variable.Variables controlling the patch phasepatchesThe list of patches. They must be in the format
accepted by the patch command, and may
optionally be compressed using gzip
(.gz), bzip2
(.bz2) or xz
(.xz).patchFlagsFlags to be passed to patch.
If not set, the argument is used, which
causes the leading directory component to be stripped from the
file names in each patch.prePatchHook executed at the start of the patch
phase.postPatchHook executed at the end of the patch
phase.The configure phaseThe configure phase prepares the source tree for building. The
default configurePhase runs
./configure (typically an Autoconf-generated
script) if it exists.Variables controlling the configure phaseconfigureScriptThe name of the configure script. It defaults to
./configure if it exists; otherwise, the
configure phase is skipped. This can actually be a command (like
perl ./Configure.pl).configureFlagsAdditional arguments passed to the configure
script.configureFlagsArrayA shell array containing additional arguments
passed to the configure script. You must use this instead of
configureFlags if the arguments contain
spaces.dontAddPrefixBy default, the flag
--prefix=$prefix is added to the configure
flags. If this is undesirable, set this variable to
true.prefixThe prefix under which the package must be
installed, passed via the option to the
configure script. It defaults to
.dontAddDisableDepTrackBy default, the flag
--disable-dependency-tracking is added to the
configure flags to speed up Automake-based builds. If this is
undesirable, set this variable to true.dontFixLibtoolBy default, the configure phase applies some
special hackery to all files called ltmain.sh
before running the configure script in order to improve the purity
of Libtool-based packagesIt clears the
sys_lib_*search_path
variables in the Libtool script to prevent Libtool from using
libraries in /usr/lib and
such.. If this is undesirable, set this
variable to true.dontDisableStaticBy default, when the configure script has
, the option
is added to the configure flags.If this is undesirable, set this variable to
true.preConfigureHook executed at the start of the configure
phase.postConfigureHook executed at the end of the configure
phase.The build phaseThe build phase is responsible for actually building the package
(e.g. compiling it). The default buildPhase
simply calls make if a file named
Makefile, makefile or
GNUmakefile exists in the current directory (or
the makefile is explicitly set); otherwise it does
nothing.Variables controlling the build phasedontBuildSet to true to skip the build phase.makefileThe file name of the Makefile.makeFlagsAdditional flags passed to
make. These flags are also used by the default
install and check phase. For setting make flags specific to the
build phase, use buildFlags (see
below).makeFlagsArrayA shell array containing additional arguments
passed to make. You must use this instead of
makeFlags if the arguments contain
spaces, e.g.
makeFlagsArray=(CFLAGS="-O0 -g" LDFLAGS="-lfoo -lbar")
Note that shell arrays cannot be passed through environment
variables, so you cannot set makeFlagsArray in
a derivation attribute (because those are passed through
environment variables): you have to define them in shell
code.buildFlags / buildFlagsArrayAdditional flags passed to
make. Like makeFlags and
makeFlagsArray, but only used by the build
phase.preBuildHook executed at the start of the build
phase.postBuildHook executed at the end of the build
phase.
You can set flags for make through the
makeFlags variable.Before and after running make, the hooks
preBuild and postBuild are
called, respectively.The check phaseThe check phase checks whether the package was built correctly
by running its test suite. The default
checkPhase calls make check,
but only if the doCheck variable is enabled.Variables controlling the check phasedoCheckIf set to a non-empty string, the check phase is
executed, otherwise it is skipped (default). Thus you should set
doCheck = true;
in the derivation to enable checks.makeFlags /
makeFlagsArray /
makefileSee the build phase for details.checkTargetThe make target that runs the tests. Defaults to
check.checkFlags / checkFlagsArrayAdditional flags passed to
make. Like makeFlags and
makeFlagsArray, but only used by the check
phase.preCheckHook executed at the start of the check
phase.postCheckHook executed at the end of the check
phase.The install phaseThe install phase is responsible for installing the package in
the Nix store under out. The default
installPhase creates the directory
$out and calls make
install.Variables controlling the install phasemakeFlags /
makeFlagsArray /
makefileSee the build phase for details.installTargetsThe make targets that perform the installation.
Defaults to install. Example:
installTargets = "install-bin install-doc";installFlags / installFlagsArrayAdditional flags passed to
make. Like makeFlags and
makeFlagsArray, but only used by the install
phase.preInstallHook executed at the start of the install
phase.postInstallHook executed at the end of the install
phase.The fixup phaseThe fixup phase performs some (Nix-specific) post-processing
actions on the files installed under $out by the
install phase. The default fixupPhase does the
following:
It moves the man/,
doc/ and info/
subdirectories of $out to
share/.It strips libraries and executables of debug
information.On Linux, it applies the patchelf
command to ELF executables and libraries to remove unused
directories from the RPATH in order to prevent
unnecessary runtime dependencies.It rewrites the interpreter paths of shell scripts
to paths found in PATH. E.g.,
/usr/bin/perl will be rewritten to
/nix/store/some-perl/bin/perl
found in PATH.Variables controlling the fixup phasedontStripIf set, libraries and executables are not
stripped. By default, they are.dontMoveSbinIf set, files in $out/sbin are not moved
to $out/bin. By default, they are.stripAllListList of directories to search for libraries and
executables from which all symbols should be
stripped. By default, it’s empty. Stripping all symbols is
risky, since it may remove not just debug symbols but also ELF
information necessary for normal execution.stripAllFlagsFlags passed to the strip
command applied to the files in the directories listed in
stripAllList. Defaults to
(i.e. ).stripDebugListList of directories to search for libraries and
executables from which only debugging-related symbols should be
stripped. It defaults to lib bin
sbin.stripDebugFlagsFlags passed to the strip
command applied to the files in the directories listed in
stripDebugList. Defaults to
(i.e. ).dontPatchELFIf set, the patchelf command is
not used to remove unnecessary RPATH entries.
Only applies to Linux.dontPatchShebangsIf set, scripts starting with
#! do not have their interpreter paths
rewritten to paths in the Nix store.forceShareThe list of directories that must be moved from
$out to $out/share.
Defaults to man doc info.setupHookA package can export a setup hook by setting this
variable. The setup hook, if defined, is copied to
$out/nix-support/setup-hook. Environment
variables are then substituted in it using substituteAll.preFixupHook executed at the start of the fixup
phase.postFixupHook executed at the end of the fixup
phase.separateDebugInfoIf set to true, the standard
environment will enable debug information in C/C++ builds. After
installation, the debug information will be separated from the
executables and stored in the output named
debug. (This output is enabled automatically;
you don’t need to set the outputs attribute
explicitly.) To be precise, the debug information is stored in
debug/lib/debug/.build-id/XX/YYYY…,
where XXYYYY… is the build
ID of the binary — a SHA-1 hash of the contents of
the binary. Debuggers like GDB use the build ID to look up the
separated debug information.For example, with GDB, you can add
set debug-file-directory ~/.nix-profile/lib/debug
to ~/.gdbinit. GDB will then be able to find
debug information installed via nix-env
-i.The distribution
phaseThe distribution phase is intended to produce a source
distribution of the package. The default
distPhase first calls make
dist, then it copies the resulting source tarballs to
$out/tarballs/. This phase is only executed if
the attribute doDist is set.Variables controlling the distribution phasedistTargetThe make target that produces the distribution.
Defaults to dist.distFlags / distFlagsArrayAdditional flags passed to
make.tarballsThe names of the source distribution files to be
copied to $out/tarballs/. It can contain
shell wildcards. The default is
*.tar.gz.dontCopyDistIf set, no files are copied to
$out/tarballs/.preDistHook executed at the start of the distribution
phase.postDistHook executed at the end of the distribution
phase.Shell functionsThe standard environment provides a number of useful
functions.substituteinfileoutfilesubsPerforms string substitution on the contents of
infile, writing the result to
outfile. The substitutions in
subs are of the following form:
s1s2Replace every occurence of the string
s1 by
s2.varNameReplace every occurence of
@varName@ by
the contents of the environment variable
varName. This is useful for
generating files from templates, using
@...@ in the
template as placeholders.varNamesReplace every occurence of
@varName@ by
the string s.Example:
substitute ./foo.in ./foo.out \
--replace /usr/bin/bar $bar/bin/bar \
--replace "a string containing spaces" "some other text" \
--subst-var someVar
substitute is implemented using the
replace
command. Unlike with the sed command, you
don’t have to worry about escaping special characters. It
supports performing substitutions on binary files (such as
executables), though there you’ll probably want to make sure
that the replacement string is as long as the replaced
string.substituteInPlacefilesubsLike substitute, but performs
the substitutions in place on the file
file.substituteAllinfileoutfileReplaces every occurence of
@varName@, where
varName is any environment variable, in
infile, writing the result to
outfile. For instance, if
infile has the contents
#! @bash@/bin/sh
PATH=@coreutils@/bin
echo @foo@
and the environment contains
bash=/nix/store/bmwp0q28cf21...-bash-3.2-p39
and
coreutils=/nix/store/68afga4khv0w...-coreutils-6.12,
but does not contain the variable foo, then the
output will be
#! /nix/store/bmwp0q28cf21...-bash-3.2-p39/bin/sh
PATH=/nix/store/68afga4khv0w...-coreutils-6.12/bin
echo @foo@
That is, no substitution is performed for undefined variables.Environment variables that start with an uppercase letter or an
underscore are filtered out,
to prevent global variables (like HOME) or private
variables (like __ETC_PROFILE_DONE) from accidentally
getting substituted.
The variables also have to be valid bash “names”, as
defined in the bash manpage (alphanumeric or _,
must not start with a number).substituteAllInPlacefileLike substituteAll, but performs
the substitutions in place on the file
file.baseHashpathsuffixStrips the directory and hash part of a store
path, storing the name part in the environment variable
strippedName. If suffix is also
provided, the suffix will also be removed. For example:
baseHash "/nix/store/9s9r019176g7cvn2nvcw41gsp862y6b4-coreutils-8.24"
# prints coreutils-8.24
baseHash "/nix/store/0016702zbydafsr20n9l1dcw7x2bf6jj-arraysugar-0.1.0.gem" .gem
# prints arraysugar-0.1.0
stripHashpathDeprecated. Use baseHash instead.Package setup hooksThe following packages provide a setup hook:
GCC wrapperAdds the include subdirectory
of each build input to the NIX_CFLAGS_COMPILE
environment variable, and the lib and
lib64 subdirectories to
NIX_LDFLAGS.PerlAdds the lib/site_perl subdirectory
of each build input to the PERL5LIB
environment variable.PythonAdds the
lib/${python.libPrefix}/site-packages subdirectory of
each build input to the PYTHONPATH environment
variable.pkg-configAdds the lib/pkgconfig and
share/pkgconfig subdirectories of each
build input to the PKG_CONFIG_PATH environment
variable.AutomakeAdds the share/aclocal
subdirectory of each build input to the ACLOCAL_PATH
environment variable.AutoconfThe autoreconfHook derivation adds
autoreconfPhase, which runs autoreconf, libtoolize and
automake, essentially preparing the configure script in autotools-based
builds.libxml2Adds every file named
catalog.xml found under the
xml/dtd and xml/xsl
subdirectories of each build input to the
XML_CATALOG_FILES environment
variable.teTeX / TeX LiveAdds the share/texmf-nix
subdirectory of each build input to the TEXINPUTS
environment variable.Qt 4Sets the QTDIR environment variable
to Qt’s path.gdk-pixbufExports GDK_PIXBUF_MODULE_FILE
environment variable the the builder. Add librsvg package
to buildInputs to get svg support.GHCCreates a temporary package database and registers
every Haskell build input in it (TODO: how?).GStreamerAdds the
GStreamer plugins subdirectory of
each build input to the GST_PLUGIN_SYSTEM_PATH_1_0 or
GST_PLUGIN_SYSTEM_PATH environment variable.Purity in Nixpkgs[measures taken to prevent dependencies on packages outside the
store, and what you can do to prevent them]GCC doesn't search in locations such as
/usr/include. In fact, attempts to add such
directories through the flag are filtered out.
Likewise, the linker (from GNU binutils) doesn't search in standard
locations such as /usr/lib. Programs built on
Linux are linked against a GNU C Library that likewise doesn't search
in the default system locations.