How to create a disk image from the command line Currently part of my build process is as follows;


Start Utilities/Disk Utility 
Select New Image 
Set Save As to widget
Set Name to widget 
Set Size to custom size 50 mb 
Set Format Mac OS Extended


but is it possible to do all this from the command line ?
You can do this with the hdiutil tool. The appropriate configuration in your case would be:

hdiutil create -size 50m -fs HFS+ -volname Widget /path/to/save/widget.dmg


Obviously change the "Widget" and path to whatever you need.

A few additional options that may be useful:


-srcfolder /path/to/source This will create the disk image with the data in the specified folder as the contents.
-megabytes 50 used instead of -size 50m. This will use binary sized megabytes (2^20 bytes) instead of decimal (10^6 bytes).
-srcdevice /dev/diskXsY This  is like srcfolder, but makes a block-based copy from another device, like a hard drive partition or DVD. Useful for making clones and images of install disks, etc.