I mounted a ISO file to my VM, click OK, everything is cool.
Then, I clicked "Edit virtual machie settings"-"CD/DVD(IDE)" in order to double check the ISO file which I mounted is correct.
Guess what, the “connection” option backs to “Use Physical Drive”! I tried several times with different ISO files, all same result.
Checked all config files, read only option is not enabled. The ISO name is standard without any special characters or space.
So, what’s wrong with my VM?