In the configuration file /etc/conf.d/dmcrypt is a example for loopback file(s) which seems to be partly wrong. The example looks like: ## Loopback file example #mount='crypt-loop-home' #source='/dev/loop0' #loop_file='/mnt/crypt/home' However, "mount='crypt-loop-home'" doesn't work and looking at the other examples it looks like it should be 'target' instead. I've tested this on my system it worked as expected. Maybe i'm wrong here, but for me it looks like 'mount' has to be replaced with 'target' Even in the Arguments overview isn't a entry for "mount"...
+ 10 Feb 2015; Michał Górny <mgorny@gentoo.org> files/1.0.6-dmcrypt.confd: + Fix example in conf.d, bug #518592, patch by Michael Mair-Keimberger.