Currently, when provisioning a new virtual machine, Foreman uses it’s default memory configuration. That may differ from the Operating System’s minimum requirements. For CentOS 7, the minimum is really 1 GB. For Fedora 27, 1 GB is often not enough – if you are doing more than a minimal install, it will fail. The fedora docs say for systems 1GB or less to use the DVD, as the network install requires more memory.

It’s not a great user experience when a user goes to provision a CentOS 7 VM, we suggest 768mb, and that fails to install. Other OS’s have similar limitations.