argv = {"nix-store", "--serve", "--write"};

            argv = {"nix-store", "--builders", "", "--serve", "--write"};

    FdSource & from, FdSink & to, const StorePathSet & paths,

    StorePathSet closure;

    to << cmdQueryValidPaths << 1 << useSubstitutes;
    writeStorePaths(*destStore, to, closure);

    auto present = readStorePaths<StorePathSet>(*destStore, from);

    auto sorted = destStore->topoSortPaths(closure);

    StorePathSet missing;

        if (!present.count(*i)) missing.insert(i->clone());

    string base(step->drvPath.to_string());

        StorePathSet inputs;
        BasicDerivation basicDrv(*step->drv);

            inputs.insert(step->drvPath.clone());

            for (auto & p : step->drv->inputSrcs)
                inputs.insert(p.clone());

        for (auto & input : step->drv->inputDrvs) {
            Derivation drv2 = readDerivation(*localStore, localStore->printStorePath(input.first));

                inputs.insert(i->second.path.clone());
                basicDrv.inputSrcs.insert(i->second.path.clone());

            copyClosure(ref<Store>(localStore), destStore, step->drv->inputSrcs, NoRepair, NoCheckSigs);

            printMsg(lvlDebug, "sending closure of ‘%s’ to ‘%s’",
                localStore->printStorePath(step->drvPath), machine->sshName);

        printMsg(lvlDebug, "building ‘%s’ on ‘%s’",
            localStore->printStorePath(step->drvPath),
            machine->sshName);

        if (sendDerivation) {
            to << cmdBuildPaths;
            writeStorePaths(*localStore, to, singleton(step->drvPath));
        } else {
            to << cmdBuildDerivation << localStore->printStorePath(step->drvPath);
            writeDerivation(to, *localStore, basicDrv);
        }

            printMsg(lvlInfo, "outputs of ‘%s’ substituted or already valid on ‘%s’",
                localStore->printStorePath(step->drvPath), machine->sshName);

            auto outputs = step->drv->outputPaths();

            to << cmdQueryPathInfos;
            writeStorePaths(*localStore, to, outputs);

            printMsg(lvlDebug, "copying outputs of ‘%s’ from ‘%s’ (%d bytes)",
                localStore->printStorePath(step->drvPath), machine->sshName, totalNarSize);

                printMsg(lvlError, "warning: had to wait %d ms for %d memory tokens for %s",
                    resMs, totalNarSize, localStore->printStorePath(step->drvPath));

            to << cmdExportPaths << 0;
            writeStorePaths(*localStore, to, outputs);