$ file -i /boot/config* /boot/config-4.10.0-38-generic: text/plain; charset=us-ascii /boot/config-4.4.0-98-generic: text/plain; charset=us-ascii
Format changed again in Xenial.
$ file -i /boot/config* 4.10.0- 38-generic: text/plain; charset=us-ascii 4.4.0-98- generic: text/plain; charset=us-ascii
/boot/config-
/boot/config-
Format changed again in Xenial.