--help Prints out a summary of the command syntax and exits. --version Prints out the Nix version number on standard output and exits. --verbose / -v Increases the level of verbosity of diagnostic messages printed on standard error. For each Nix operation, the information printed on standard output is well-defined; any diagnostic information is printed on standard error, never on standard output. This option may be specified repeatedly. Currently, the following verbosity levels exist: 0 Errors only: only print messages explaining why the Nix invocation failed. 1 Informational: print useful messages about what Nix is doing. 2 Talkative: print more informational messages. 3 Chatty: print even more informational messages. 4 Debug: print debug information: 5 Vomit: print vast amounts of debug information. --build-output / -B Causes the output written by build actions to standard output and standard error to be echoed to standard error, regardless of verbosity level. By default, it is only echoed at a verbosity level of at least 4 (Debug), and is suppressed at lower levels. Note that it is always written to a log file in prefix/nix/var/log/nix. --max-jobs / -j Sets the maximum number of build jobs that Nix will perform in parallel to the specified number. The default is 1. A higher value is useful on SMP systems or to exploit I/O latency. --keep-going / -k Keep going in case of failed builds, to the greatest extent possible. That is, if building an input of some derivation fails, Nix will still build the other inputs, but not the derivation itself. Without this option, Nix stops if any build fails (except for builds of substitutes), possibly killing builds in progress (in case of parallel or distributed builds). --keep-failed / -K Specifies that in case of a build failure, the temporary directory (usually in /tmp) in which the build takes place should not be deleted. The path of the build directory is printed as an informational message.