Output debug to file from 'npm install' via maven frontend plugin or via commandline options?

We use maven + frontend to execute npm, node and ember to create an ember app. Sometimes this process hangs on 'npm install' with no useful data in log files. I'd like to:

• get better insight by increasing log level
• avoid obscuring other log info with debug messages

In a perfect world, I'd add command line options to

• set npm commands log level to debug
• output to a file

Then, I'd use a maven profile for ensure the build system always logs with max verbosity while still allowing developers to see important log info.

If you can tell me the command line options or file settings or direct me to the relevant docs then I'll happily modify my pom and post that as a solution here.

Thanks

Peter