This seems to be a kernel regression that happened either in 4.4 or 4.2.
I'll get more information on recreate soon. to get this off my system, here are my very sloppy notes http://paste.ubuntu.com/23117619/
essentially, you boot a cloud image with overlayroot enabled then 'apt-key add - <some-file'.
Also can be recreated with a tempfile rename for some files. Ie, the way that atomic writes are often done, by writing to afile in the same dir and then renaming.
This seems to be a kernel regression that happened either in 4.4 or 4.2.
I'll get more information on recreate soon. to get this off my system, here are my very sloppy notes http:// paste.ubuntu. com/23117619/
essentially, you boot a cloud image with overlayroot enabled then 'apt-key add - <some-file'.
Also can be recreated with a tempfile rename for some files. Ie, the way that atomic writes are often done, by writing to afile in the same dir and then renaming.