pipeline-on-a-stick unmount error

[wmkouw]

Goal: write black-box NewsReader pipeline on USB-stick.

Input: followed instructions on website. First, I formatted my USB-stick and downloaded the filesystem. Then I plugged it in and unmounted it. Afterwards, I ran:

sudo dd bs=1MB if=20160616_poas_fs of=/dev/sdc

Problem: command completes, but when trying to unmount, an error pops up that the system is still writing to stick. After waiting a night, the error remains. After forcibly unmounting the stick and plugging it back in, the system does not register any device. Mount commands do not work either.