hmm..thanks for the idea. I tried this, but couldn't get it to boot..
after dd the partition was no longer ext4 and no longer recognized.
I ended up using clonezilla to create and restore an image. Took me most of a day to figure out that:
A. you can't use USB drive to save the partition in clonezilla via vm, but you can create a network share of the USB to do it
B. for some reason I needed to go into the expert settings and have clonezilla repair the filesystem (-fsck-src-part)
C. you can't restore to a diff partition (eg sda1 -> sda4) without renaming the image file (completely stupid, I know!)