private BesuController createController() {
      try {
        // Set some defaults
        return parentCommand
            .parentCommand
            .setupControllerBuilder()
            // set to mainnet genesis block so validation rules won't reject it.
            .clock(Clock.fixed(Instant.ofEpochSecond(startTime), ZoneOffset.UTC))
            .miningParameters(getMiningParameters())
            .build();
      } catch (final Exception e) {
        throw new ExecutionException(parentCommand.spec.commandLine(), e.getMessage(), e);
      }
    }
blocks import sub-command

<p>Imports blocks from a file into the database
app/src/main/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommand.java