When installing IDM 12.6 SP6, you have to select an object store. When installing in console mode ( ./install -i console) there is a known bug where it complains about "Host Name Cannot Be Blank". In order to get around this problem either install the product in silent mode (https://wiki.ca.com/display/CIM12606/Silent+Installation) or use UI via XManager. You will then be able to successfully be able to install the product on linux.
A defect has been submitted to sustaining engineering. EDIT: Fixed in 12.6 SP6 CR1 and 12.6 SP7