Today I decided to install Tails to a flash drive that was not being used. While I have my system set to dual boot between Xenial and Windows 7, it is unusual for the Windows system to launch at all, unless I’m in the mood to stream Steam games over moonlight. The choices offered at the Tails website are to install from another Tails installation, or install straight from Ubuntu. Since I was using Tails for the first time in about 3 years, I chose to go straight from Ubuntu. This involved following the steps provided on the Tails website, with one small addition. Every time I tried to install, wipefs failed, and I was unable to figure out why, until the Eureka moment struck. My usb drive is set to automount on insert, and it was mounted.
The solution was simple. Unmount the drive and then run the installer. While it was a simple solution, it might be beneficial to include a warning that tails-installer will not work if the drive your are installing to is already mounted. I’ve run dd multiple times with mounted disks and never experience this issue. Hopefully my simple solution will help you with keeping your private life private, and making life easier for yourself.