Nodejs/npm: How to reinstall/recompile copied app packages

Question

Setup:

• A VM with an Internet connection where npm install will be executed to install all the app dependencies. The result will be a folder with the app and its dependencies in node_modules.

• Between the app modules is fi: mongoose, which on installation time uses node-gyp to compile a native BSON extension.

• The app folder is copied to another VM without an Internet conection and it is fully functional, but then the compiled extensions don't work but its .js fallbacks does.

Question:

How can I reinstall/recompile/regenerate all the app modules on the new VM without an Internet conection?

Solution

This is precisely what the npm rebuild command does. Just run npm rebuild inside your app directory after it is copied over to the new VM and any binary add-ons will be recompiled to match the current CPU architecture and node version. If the initial npm install before the copy was completely successful, the npm rebuild on the second VM will not need to download anything. Just make sure the second VM has a reasonably-close version of node and the appropriate lower level compilers, libraries, etc (build-essential and python on debian, for example).