Cisco IOU is quite complicate to integrate, it needs 32-bit shared libraries, a special NETMAP configuration file and iouyap (https://github.com/GNS3/iouyap) to communicate to the outside world.
To ease that, this image packs all the necessary tools in a base image.
create-iou-image <image> <license> <startup-config> [<private-config>]
the user creates new self-contained docker IOU images by adding the IOU
binary, license and startup configuration to this base image.
docker build -t iou-base .
The 32-bit libraries were copied from Debian 8 (Jessie) by