Officially it is not possible to host a private separate “web server” on a single bay My Cloud unit (gen 1 or gen 2). Unofficially it may be possible but it is NOT supported by Western Digital. For generation 1 (v3.x/v4.x firmware) one can use an alternate firmware OS, see this link. For the newer generation 2 (v2.x firmware) one can try enabling the app tab as detailed in the following post and then use Joomla.
http://wdstagingsplit.staged-by-discourse.com/t/wd-mycloud-gen2-enable-apps-install-tab-apps/177885
