c0d4173263
Some benchmarking suggested this as a good value. Running $ benchmark -f ... -t 25 -- sh -c 'rm -f /nix/var/nix/binary-cache*; nix-store -r /nix/store/x5z8a2yvz8h6ccmhwrwrp9igg03575jg-nixos-15.09.git.5fd87e1M.drv --dry-run --option binary-caches-parallel-connections <N>' gave the following mean elapsed times for these values of N: N=10: 3.3541 N=20: 2.9320 N=25: 2.6690 N=30: 2.9417 N=50: 3.2021 N=100: 3.5718 N=150: 4.2079 Memory usage is also reduced (N=150 used 186 MB, N=25 only 68 MB). Closes #708.
639 lines
24 KiB
XML
639 lines
24 KiB
XML
<refentry xmlns="http://docbook.org/ns/docbook"
|
||
xmlns:xlink="http://www.w3.org/1999/xlink"
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||
xmlns:xi="http://www.w3.org/2001/XInclude"
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||
xml:id="sec-conf-file">
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||
|
||
<refmeta>
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||
<refentrytitle>nix.conf</refentrytitle>
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||
<manvolnum>5</manvolnum>
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||
<refmiscinfo class="source">Nix</refmiscinfo>
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||
<refmiscinfo class="version"><xi:include href="../version.txt" parse="text"/></refmiscinfo>
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||
</refmeta>
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||
|
||
<refnamediv>
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||
<refname>nix.conf</refname>
|
||
<refpurpose>Nix configuration file</refpurpose>
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||
</refnamediv>
|
||
|
||
<refsection><title>Description</title>
|
||
|
||
<para>A number of persistent settings of Nix are stored in the file
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||
<filename><replaceable>sysconfdir</replaceable>/nix/nix.conf</filename>.
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||
This file is a list of <literal><replaceable>name</replaceable> =
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||
<replaceable>value</replaceable></literal> pairs, one per line.
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||
Comments start with a <literal>#</literal> character. Here is an example
|
||
configuration file:</para>
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||
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||
<programlisting>
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||
gc-keep-outputs = true # Nice for developers
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||
gc-keep-derivations = true # Idem
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||
env-keep-derivations = false
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||
</programlisting>
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||
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||
<para>You can override settings using the <option>--option</option>
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||
flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
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||
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||
<para>The following settings are currently available:
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||
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||
<variablelist>
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||
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||
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||
<varlistentry xml:id="conf-gc-keep-outputs"><term><literal>gc-keep-outputs</literal></term>
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||
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||
<listitem><para>If <literal>true</literal>, the garbage collector
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||
will keep the outputs of non-garbage derivations. If
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<literal>false</literal> (default), outputs will be deleted unless
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they are GC roots themselves (or reachable from other roots).</para>
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||
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||
<para>In general, outputs must be registered as roots separately.
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||
However, even if the output of a derivation is registered as a
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root, the collector will still delete store paths that are used
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only at build time (e.g., the C compiler, or source tarballs
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downloaded from the network). To prevent it from doing so, set
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||
this option to <literal>true</literal>.</para></listitem>
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</varlistentry>
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<varlistentry xml:id="conf-gc-keep-derivations"><term><literal>gc-keep-derivations</literal></term>
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<listitem><para>If <literal>true</literal> (default), the garbage
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collector will keep the derivations from which non-garbage store
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paths were built. If <literal>false</literal>, they will be
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deleted unless explicitly registered as a root (or reachable from
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other roots).</para>
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<para>Keeping derivation around is useful for querying and
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traceability (e.g., it allows you to ask with what dependencies or
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options a store path was built), so by default this option is on.
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Turn it off to save a bit of disk space (or a lot if
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<literal>gc-keep-outputs</literal> is also turned on).</para></listitem>
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</varlistentry>
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<varlistentry><term><literal>env-keep-derivations</literal></term>
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<listitem><para>If <literal>false</literal> (default), derivations
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are not stored in Nix user environments. That is, the derivation
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any build-time-only dependencies may be garbage-collected.</para>
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<para>If <literal>true</literal>, when you add a Nix derivation to
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a user environment, the path of the derivation is stored in the
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user environment. Thus, the derivation will not be
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garbage-collected until the user environment generation is deleted
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(<command>nix-env --delete-generations</command>). To prevent
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build-time-only dependencies from being collected, you should also
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turn on <literal>gc-keep-outputs</literal>.</para>
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<para>The difference between this option and
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<literal>gc-keep-derivations</literal> is that this one is
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“sticky”: it applies to any user environment created while this
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option was enabled, while <literal>gc-keep-derivations</literal>
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only applies at the moment the garbage collector is
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run.</para></listitem>
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</varlistentry>
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<varlistentry xml:id="conf-build-max-jobs"><term><literal>build-max-jobs</literal></term>
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<listitem><para>This option defines the maximum number of jobs
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that Nix will try to build in parallel. The default is
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<literal>1</literal>. You should generally set it to the number
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of CPUs in your system (e.g., <literal>2</literal> on an Athlon 64
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X2). It can be overridden using the <option
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linkend='opt-max-jobs'>--max-jobs</option> (<option>-j</option>)
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command line switch.</para></listitem>
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</varlistentry>
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<varlistentry xml:id="conf-build-cores"><term><literal>build-cores</literal></term>
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<listitem><para>Sets the value of the
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<envar>NIX_BUILD_CORES</envar> environment variable in the
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invocation of builders. Builders can use this variable at their
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discretion to control the maximum amount of parallelism. For
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instance, in Nixpkgs, if the derivation attribute
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<varname>enableParallelBuilding</varname> is set to
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<literal>true</literal>, the builder passes the
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<option>-j<replaceable>N</replaceable></option> flag to GNU Make.
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It can be overridden using the <option
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linkend='opt-cores'>--cores</option> command line switch and
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defaults to <literal>1</literal>. The value <literal>0</literal>
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means that the builder should use all available CPU cores in the
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system.</para></listitem>
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</varlistentry>
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<varlistentry xml:id="conf-build-max-silent-time"><term><literal>build-max-silent-time</literal></term>
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<listitem>
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<para>This option defines the maximum number of seconds that a
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builder can go without producing any data on standard output or
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standard error. This is useful (for instance in an automated
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build system) to catch builds that are stuck in an infinite
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loop, or to catch remote builds that are hanging due to network
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||
problems. It can be overridden using the <option
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||
linkend="opt-max-silent-time">--max-silent-time</option> command
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||
line switch.</para>
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<para>The value <literal>0</literal> means that there is no
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timeout. This is also the default.</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="conf-build-timeout"><term><literal>build-timeout</literal></term>
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<listitem>
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<para>This option defines the maximum number of seconds that a
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builder can run. This is useful (for instance in an automated
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build system) to catch builds that are stuck in an infinite loop
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but keep writing to their standard output or standard error. It
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can be overridden using the <option
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linkend="opt-timeout">--timeout</option> command line
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||
switch.</para>
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||
|
||
<para>The value <literal>0</literal> means that there is no
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timeout. This is also the default.</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="conf-build-max-log-size"><term><literal>build-max-log-size</literal></term>
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<listitem>
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||
|
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<para>This option defines the maximum number of bytes that a
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builder can write to its stdout/stderr. If the builder exceeds
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this limit, it’s killed. A value of <literal>0</literal> (the
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default) means that there is no limit.</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="conf-build-users-group"><term><literal>build-users-group</literal></term>
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<listitem><para>This options specifies the Unix group containing
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the Nix build user accounts. In multi-user Nix installations,
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builds should not be performed by the Nix account since that would
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allow users to arbitrarily modify the Nix store and database by
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supplying specially crafted builders; and they cannot be performed
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by the calling user since that would allow him/her to influence
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the build result.</para>
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<para>Therefore, if this option is non-empty and specifies a valid
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group, builds will be performed under the user accounts that are a
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member of the group specified here (as listed in
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<filename>/etc/group</filename>). Those user accounts should not
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be used for any other purpose!</para>
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<para>Nix will never run two builds under the same user account at
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the same time. This is to prevent an obvious security hole: a
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malicious user writing a Nix expression that modifies the build
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result of a legitimate Nix expression being built by another user.
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Therefore it is good to have as many Nix build user accounts as
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you can spare. (Remember: uids are cheap.)</para>
|
||
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<para>The build users should have permission to create files in
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the Nix store, but not delete them. Therefore,
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<filename>/nix/store</filename> should be owned by the Nix
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account, its group should be the group specified here, and its
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mode should be <literal>1775</literal>.</para>
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<para>If the build users group is empty, builds will be performed
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||
under the uid of the Nix process (that is, the uid of the caller
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||
if <envar>NIX_REMOTE</envar> is empty, the uid under which the Nix
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||
daemon runs if <envar>NIX_REMOTE</envar> is
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<literal>daemon</literal>). Obviously, this should not be used in
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multi-user settings with untrusted users.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term><literal>build-use-sandbox</literal></term>
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<listitem><para>If set to <literal>true</literal>, builds will be
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||
performed in a <emphasis>sandboxed environment</emphasis>, i.e.,
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||
they’re isolated from the normal file system hierarchy and will
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||
only see their dependencies in the Nix store, the temporary build
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||
directory, private versions of <filename>/proc</filename>,
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||
<filename>/dev</filename>, <filename>/dev/shm</filename> and
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||
<filename>/dev/pts</filename> (on Linux), and the paths configured with the
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||
<link linkend='conf-build-sandbox-paths'><literal>build-sandbox-paths</literal>
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||
option</link>. This is useful to prevent undeclared dependencies
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||
on files in directories such as <filename>/usr/bin</filename>. In
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||
addition, on Linux, builds run in private PID, mount, network, IPC
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||
and UTS namespaces to isolate them from other processes in the
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||
system (except that fixed-output derivations do not run in private
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network namespace to ensure they can access the network).</para>
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<para>Currently, sandboxing only work on Linux and Mac OS X. The use
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of a sandbox requires that Nix is run as root (so you should use
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||
the <link linkend='conf-build-users-group'>“build users”
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||
feature</link> to perform the actual builds under different users
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than root).</para>
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<para>If this option is set to <literal>relaxed</literal>, then
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fixed-output derivations and derivations that have the
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<varname>__noChroot</varname> attribute set to
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||
<literal>true</literal> do not run in sandboxes.</para>
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||
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||
<para>The default is <literal>false</literal>.</para>
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</listitem>
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||
</varlistentry>
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||
<varlistentry xml:id="conf-build-sandbox-paths">
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<term><literal>build-sandbox-paths</literal></term>
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<listitem><para>A list of paths bind-mounted into Nix sandbox
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environments. You can use the syntax
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||
<literal><replaceable>target</replaceable>=<replaceable>source</replaceable></literal>
|
||
to mount a path in a different location in the sandbox; for
|
||
instance, <literal>/bin=/nix-bin</literal> will mount the path
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||
<literal>/nix-bin</literal> as <literal>/bin</literal> inside the
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sandbox.</para>
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||
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||
<para>Depending on how Nix was built, the default value for this option
|
||
may be empty or provide <filename>/bin/sh</filename> as a
|
||
bind-mount of <command>bash</command>.</para></listitem>
|
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|
||
</varlistentry>
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<varlistentry xml:id="conf-build-extra-sandbox-paths">
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<term><literal>build-extra-sandbox-paths</literal></term>
|
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|
||
<listitem><para>A list of additional paths appended to
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||
<option>build-sandbox-paths</option>. Useful if you want to extend
|
||
its default value.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>build-use-substitutes</literal></term>
|
||
|
||
<listitem><para>If set to <literal>true</literal> (default), Nix
|
||
will use binary substitutes if available. This option can be
|
||
disabled to force building from source.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>build-fallback</literal></term>
|
||
|
||
<listitem><para>If set to <literal>true</literal>, Nix will fall
|
||
back to building from source if a binary substitute fails. This
|
||
is equivalent to the <option>--fallback</option> flag. The
|
||
default is <literal>false</literal>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>build-cache-failure</literal></term>
|
||
|
||
<listitem><para>If set to <literal>true</literal>, Nix will
|
||
“cache” build failures, meaning that it will remember (in its
|
||
database) that a derivation previously failed. If you then try to
|
||
build the derivation again, Nix will immediately fail rather than
|
||
perform the build again. Failures in fixed-output derivations
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||
(such as <function>fetchurl</function> calls) are never cached.
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||
The “failed” status of a derivation can be cleared using
|
||
<command>nix-store --clear-failed-paths</command>. By default,
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||
failure caching is disabled.</para></listitem>
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||
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||
</varlistentry>
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||
<varlistentry><term><literal>build-keep-log</literal></term>
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<listitem><para>If set to <literal>true</literal> (the default),
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Nix will write the build log of a derivation (i.e. the standard
|
||
output and error of its builder) to the directory
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||
<filename>/nix/var/log/nix/drvs</filename>. The build log can be
|
||
retrieved using the command <command>nix-store -l
|
||
<replaceable>path</replaceable></command>.</para></listitem>
|
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||
</varlistentry>
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||
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||
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||
<varlistentry><term><literal>build-compress-log</literal></term>
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||
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||
<listitem><para>If set to <literal>true</literal> (the default),
|
||
build logs written to <filename>/nix/var/log/nix/drvs</filename>
|
||
will be compressed on the fly using bzip2. Otherwise, they will
|
||
not be compressed.</para></listitem>
|
||
|
||
</varlistentry>
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||
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||
|
||
<varlistentry><term><literal>use-binary-caches</literal></term>
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||
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||
<listitem><para>If set to <literal>true</literal> (the default),
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||
Nix will check the binary caches specified by
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||
<option>binary-caches</option> and related options to obtain
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binary substitutes.</para></listitem>
|
||
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||
</varlistentry>
|
||
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||
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||
<varlistentry><term><literal>binary-caches</literal></term>
|
||
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<listitem><para>A list of URLs of binary caches, separated by
|
||
whitespace. The default is
|
||
<literal>https://cache.nixos.org</literal>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>binary-caches-files</literal></term>
|
||
|
||
<listitem><para>A list of names of files that will be read to
|
||
obtain additional binary cache URLs. The default is
|
||
<literal>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels/binary-caches/*</literal>.
|
||
Note that when you’re using the Nix daemon,
|
||
<replaceable>username</replaceable> is always equal to
|
||
<literal>root</literal>, so Nix will only use the binary caches
|
||
provided by the channels installed by root. Do not set this
|
||
option to read files created by untrusted users!</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>trusted-binary-caches</literal></term>
|
||
|
||
<listitem><para>A list of URLs of binary caches, separated by
|
||
whitespace. These are not used by default, but can be enabled by
|
||
users of the Nix daemon by specifying <literal>--option
|
||
binary-caches <replaceable>urls</replaceable></literal> on the
|
||
command line. Unprivileged users are only allowed to pass a
|
||
subset of the URLs listed in <literal>binary-caches</literal> and
|
||
<literal>trusted-binary-caches</literal>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>extra-binary-caches</literal></term>
|
||
|
||
<listitem><para>Additional binary caches appended to those
|
||
specified in <option>binary-caches</option> and
|
||
<option>binary-caches-files</option>. When used by unprivileged
|
||
users, untrusted binary caches (i.e. those not listed in
|
||
<option>trusted-binary-caches</option>) are silently
|
||
ignored.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>signed-binary-caches</literal></term>
|
||
|
||
<listitem><para>If set to <literal>*</literal>, Nix will only
|
||
download binaries if they are signed using one of the keys listed
|
||
in <option>binary-cache-public-keys</option>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>binary-cache-public-keys</literal></term>
|
||
|
||
<listitem><para>A whitespace-separated list of public keys
|
||
corresponding to the secret keys trusted to sign binary
|
||
caches. For example:
|
||
<literal>cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
|
||
hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=</literal>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>binary-caches-parallel-connections</literal></term>
|
||
|
||
<listitem><para>The maximum number of parallel HTTP connections
|
||
used by the binary cache substituter to get NAR info files. This
|
||
number should be high to minimise latency. It defaults to
|
||
25.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>verify-https-binary-caches</literal></term>
|
||
|
||
<listitem><para>Whether HTTPS binary caches are required to have a
|
||
certificate that can be verified. Defaults to
|
||
<literal>true</literal>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>force-manifest</literal></term>
|
||
|
||
<listitem><para>If this option is set to <literal>false</literal>
|
||
(default) and a Nix channel provides both a manifest and a binary
|
||
cache, only the binary cache will be used. If set to
|
||
<literal>true</literal>, the manifest will be fetched as well.
|
||
This is useful if you want to use binary patches (which are
|
||
currently not supported by binary caches).</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>system</literal></term>
|
||
|
||
<listitem><para>This option specifies the canonical Nix system
|
||
name of the current installation, such as
|
||
<literal>i686-linux</literal> or
|
||
<literal>powerpc-darwin</literal>. Nix can only build derivations
|
||
whose <literal>system</literal> attribute equals the value
|
||
specified here. In general, it never makes sense to modify this
|
||
value from its default, since you can use it to ‘lie’ about the
|
||
platform you are building on (e.g., perform a Mac OS build on a
|
||
Linux machine; the result would obviously be wrong). It only
|
||
makes sense if the Nix binaries can run on multiple platforms,
|
||
e.g., ‘universal binaries’ that run on <literal>powerpc-darwin</literal> and
|
||
<literal>i686-darwin</literal>.</para>
|
||
|
||
<para>It defaults to the canonical Nix system name detected by
|
||
<filename>configure</filename> at build time.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>fsync-metadata</literal></term>
|
||
|
||
<listitem><para>If set to <literal>true</literal>, changes to the
|
||
Nix store metadata (in <filename>/nix/var/nix/db</filename>) are
|
||
synchronously flushed to disk. This improves robustness in case
|
||
of system crashes, but reduces performance. The default is
|
||
<literal>true</literal>.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry><term><literal>auto-optimise-store</literal></term>
|
||
|
||
<listitem><para>If set to <literal>true</literal>, Nix
|
||
automatically detects files in the store that have identical
|
||
contents, and replaces them with hard links to a single copy.
|
||
This saves disk space. If set to <literal>false</literal> (the
|
||
default), you can still run <command>nix-store
|
||
--optimise</command> to get rid of duplicate
|
||
files.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-connect-timeout"><term><literal>connect-timeout</literal></term>
|
||
|
||
<listitem>
|
||
|
||
<para>The timeout (in seconds) for establishing connections in
|
||
the binary cache substituter. It corresponds to
|
||
<command>curl</command>’s <option>--connect-timeout</option>
|
||
option.</para>
|
||
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-log-servers"><term><literal>log-servers</literal></term>
|
||
|
||
<listitem>
|
||
|
||
<para>A list of URL prefixes (such as
|
||
<literal>http://hydra.nixos.org/log</literal>) from which
|
||
<command>nix-store -l</command> will try to fetch build logs if
|
||
they’re not available locally.</para>
|
||
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-trusted-users"><term><literal>trusted-users</literal></term>
|
||
|
||
<listitem>
|
||
|
||
<para>A list of names of users (separated by whitespace) that
|
||
have additional rights when connecting to the Nix daemon, such
|
||
as the ability to specify additional binary caches, or to import
|
||
unsigned NARs. You can also specify groups by prefixing them
|
||
with <literal>@</literal>; for instance,
|
||
<literal>@wheel</literal> means all users in the
|
||
<literal>wheel</literal> group. The default is
|
||
<literal>root</literal>.</para>
|
||
|
||
<warning><para>The users listed here have the ability to
|
||
compromise the security of a multi-user Nix store. For instance,
|
||
they could install Trojan horses subsequently executed by other
|
||
users. So you should consider carefully whether to add users to
|
||
this list.</para></warning>
|
||
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-allowed-users"><term><literal>allowed-users</literal></term>
|
||
|
||
<listitem>
|
||
|
||
<para>A list of names of users (separated by whitespace) that
|
||
are allowed to connect to the Nix daemon. As with the
|
||
<option>trusted-users</option> option, you can specify groups by
|
||
prefixing them with <literal>@</literal>. Also, you can allow
|
||
all users by specifying <literal>*</literal>. The default is
|
||
<literal>*</literal>.</para>
|
||
|
||
<para>Note that trusted users are always allowed to connect.</para>
|
||
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-restrict-eval"><term><literal>restrict-eval</literal></term>
|
||
|
||
<listitem>
|
||
|
||
<para>If set to <literal>true</literal>, the Nix evaluator will
|
||
not allow access to any files outside of the Nix search path (as
|
||
set via the <envar>NIX_PATH</envar> environment variable or the
|
||
<option>-I</option> option). The default is
|
||
<literal>false</literal>.</para>
|
||
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-pre-build-hook"><term><literal>pre-build-hook</literal></term>
|
||
|
||
<listitem>
|
||
|
||
|
||
<para>If set, the path to a program that can set extra
|
||
derivation-specific settings for this system. This is used for settings
|
||
that can't be captured by the derivation model itself and are too variable
|
||
between different versions of the same system to be hard-coded into nix.
|
||
</para>
|
||
|
||
<para>The hook is passed the derivation path and, if sandboxes are enabled,
|
||
the sandbox directory. It can then modify the sandbox and send a series of
|
||
commands to modify various settings to stdout. The currently recognized
|
||
commands are:</para>
|
||
|
||
<variablelist>
|
||
<varlistentry xml:id="extra-sandbox-paths">
|
||
<term><literal>extra-sandbox-paths</literal></term>
|
||
|
||
<listitem>
|
||
|
||
<para>Pass a list of files and directories to be included in the
|
||
sandbox for this build. One entry per line, terminated by an empty
|
||
line. Entries have the same format as
|
||
<literal>build-sandbox-paths</literal>.</para>
|
||
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
</variablelist>
|
||
</listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
<varlistentry xml:id="conf-build-repeat"><term><literal>build-repeat</literal></term>
|
||
|
||
<listitem><para>How many times to repeat builds to check whether
|
||
they are deterministic. The default value is 0. If the value is
|
||
non-zero, every build is repeated the specified number of
|
||
times. If the contents of any of the runs differs from the
|
||
previous ones, the build is rejected and the resulting store paths
|
||
are not registered as “valid” in Nix’s database.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
|
||
</variablelist>
|
||
|
||
</para>
|
||
|
||
</refsection>
|
||
|
||
</refentry>
|