I cannot create a non-Windows virtual machine. The New Virtual Machine Wizard cannot automatically detect the installation media (a CD/DVD or an .iso file). When adding the installation media manually the following warning is displayed:
"Unable to detect operating system. Click continue to proceed anyway or try another source"
Click Continue then choose the OS type that suites you the most:
NOTE: Many Linux distributions are based on other mainstream distributions. For example Puppy Linux 5.2.8 and Bodhi Linux are based on Ubuntu. Thus you may want to choose either a particular mainstream OS type or other general type, like "Other Linux" or "Other Linux kernel 2.x"
Continue with the guest OS installation.
NOTE: You may want to follow the installation guides for the particular OS distributions available at their official websites