this was a clean install, so i don't have any file in it. i'm trying to boot it with high sierra disk utility but it don't show the hdd. so how can i erase that drive if disk utility not shows the drive? do i need an other mac or pc?If you are booting to an older system (El Capitan or older), then Disk Utility will NOT show an APFS format drive. It's not a supported format before Sierra, and won't be visible at all.
If you have upgraded to High Sierra beta, and you have a Recovery system upgraded as well, then the APFS drive should be visible when you are booted to the recovery system.
But, I don't think you can successfully convert a (spinning) HDD to APFS.
So, if you still have the spinning hard drive, you will likely need to erase that drive, then reinstall macOS, then get your other apps and files from your backup.
You DO have a current backup, correct?
Boot into recovery console -hold down Apple and R key and run disk utility from there. Does it show your drive?i converted my hd to apfs but, after the reboot my mac doesn't find Macintosh HD. I tried from disk utility but it is disappeared. Please help me. mac mini late 2012 with original hdd
you should clean install high Sierra tformatting your hd in HFS+ so that high Sierra can install a required firmware upgrade to support apfs. It starts the install, reboots, you'll ear a BONG, it'll appear the apple logo and a big progress bar (DON'T interrupt), it'll restart again with normal progress bar. Only after that your Mac will be able to "see" apfs volumes.i converted my hd to apfs but, after the reboot my mac doesn't find Macintosh HD. I tried from disk utility but it is disappeared. Please help me. mac mini late 2012 with original hdd