91dc023665
Whenever Nix attempts to realise a derivation for which a closure is already known, but this closure cannot be realised, fall back on normalising the derivation. The most common scenario in which this is useful is when we have registered substitutes in order to perform binary distribution from, say, a network repository. If the repository is down, the realisation of the derivation will fail. When this option is specified, Nix will build the derivation instead. Thus, binary installation falls back on a source installation. This option is not the default since it is generally not desirable for a transient failure in obtaining the substitutes to lead to a full build from source (with the related consumption of resources).
174 lines
5.1 KiB
XML
174 lines
5.1 KiB
XML
<varlistentry>
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<term><option>--help</option></term>
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<listitem>
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<para>
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Prints out a summary of the command syntax and exits.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--version</option></term>
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<listitem>
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<para>
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Prints out the Nix version number on standard output and exits.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--verbose</option> / <option>-v</option></term>
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<listitem>
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<para>
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Increases the level of verbosity of diagnostic messages printed
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on standard error. For each Nix operation, the information
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printed on standard output is well-defined; any diagnostic
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information is printed on standard error, never on standard
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output.
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</para>
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<para>
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This option may be specified repeatedly. Currently, the
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following verbosity levels exist:
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</para>
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<variablelist>
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<varlistentry>
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<term>0</term>
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<listitem>
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<para>
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<quote>Errors only</quote>: only print messages explaining
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why the Nix invocation failed.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>1</term>
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<listitem>
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<para>
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<quote>Informational</quote>: print
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<emphasis>useful</emphasis> messages about what Nix is
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doing.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>2</term>
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<listitem>
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<para>
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<quote>Talkative</quote>: print more informational messages.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>3</term>
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<listitem>
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<para>
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<quote>Chatty</quote>: print even more informational messages.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>4</term>
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<listitem>
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<para>
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<quote>Debug</quote>: print debug information:
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>5</term>
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<listitem>
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<para>
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<quote>Vomit</quote>: print vast amounts of debug
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information.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--build-output</option> / <option>-B</option></term>
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<listitem>
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<para>
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Causes the output written by build actions to standard output
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and standard error to be echoed to standard error, regardless of
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verbosity level. By default, it is only echoed at a verbosity
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level of at least 4 (<quote>Debug</quote>), and is suppressed at
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lower levels. Note that it is always written to a log file in
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<filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--max-jobs</option> / <option>-j</option></term>
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<listitem>
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<para>
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Sets the maximum number of build jobs that Nix will perform in
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parallel to the specified number. The default is 1. A higher
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value is useful on SMP systems or to exploit I/O latency.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--keep-going</option> / <option>-k</option></term>
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<listitem>
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<para>
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Keep going in case of failed builds, to the greatest extent
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possible. That is, if building an input of some derivation
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fails, Nix will still build the other inputs, but not the
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derivation itself. Without this option, Nix stops if any build
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fails (except for builds of substitutes), possibly killing
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builds in progress (in case of parallel or distributed builds).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--keep-failed</option> / <option>-K</option></term>
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<listitem>
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<para>
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Specifies that in case of a build failure, the temporary
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directory (usually in <filename>/tmp</filename>) in which the
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build takes place should not be deleted. The path of the build
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directory is printed as an informational message.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--fallback</option></term>
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<listitem>
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<para>
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Whenever Nix attempts to realise a derivation for which a
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closure is already known, but this closure cannot be realised,
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fall back on normalising the derivation.
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</para>
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<para>
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The most common scenario in which this is useful is when we have
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registered substitutes in order to perform binary distribution
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from, say, a network repository. If the repository is down, the
|
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realisation of the derivation will fail. When this option is
|
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specified, Nix will build the derivation instead. Thus,
|
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binary installation falls back on a source installation. This
|
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option is not the default since it is generally not desirable
|
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for a transient failure in obtaining the substitutes to lead to
|
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a full build from source (with the related consumption of
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resources).
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</para>
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</listitem>
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</varlistentry>
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