createinstallmedia

This command is handy for creating bootable OSX media.

Make a Mac OS install thumb drive

The main help page I found for this tool is on Apple's site but the TLDR version is:

1. Download MacOS Sierra from the App Store.

2. If the OSX installer launches, quit it.

3. Put in the USB drive you want to load the bootable install on, and issue this in terminal (assuming MY-USB-DRIVE is your USB drive):

sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MY-USB-DRIVE/ --application /Applications/Install\ macOS\ Sierra.app