184 lines
		
	
	
	
		
			5.3 KiB
		
	
	
	
		
			XML
		
	
	
	
	
	
			
		
		
	
	
			184 lines
		
	
	
	
		
			5.3 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.  This is the default.
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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>--no-build-output</option> / <option>-Q</option></term>
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  <listitem>
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    <para>
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      By default, output written by builders to standard output and
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      standard error is echoed to the Nix command's standard error.
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      This option suppresses this behaviour.  Note that the builder's
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      standard output and error are 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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<varlistentry>
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  <term><option>--readonly-mode</option></term>
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  <listitem>
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    <para>
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      When this option is used, no attempt is made to open the Nix
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      database.  Most Nix operations do need database access, so those
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      operations will fail.
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    </para>
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  </listitem>
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</varlistentry>
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