I had Kali and Linux Mint installed and erased Mint to install Centos7. Grub was totally deleted and I could only boot into grub recovery. Many hours of cussing later I got Kali back, I can see Centos filesystem mounted on my desktop and in disk utility. I never finished setting Centos up as I was rushed out the door which probably caused the problem in the first place, for some reason it's raid and although it's 2 harddrives they are not set up for raid and 1 is Kali and 1 is Centos. The Centos boot folder is still empty after running grub-install on it twice and it does not show in grub. How do I get Centos as an option?

Did you run update-grub in kali to get a boot entry for centos
Is it empty as in no grub folder or empty as in nothing at all? If empty as in nothing no kernels no nothing then you don't have a complete centos install.

VERY odd
cent's installer is very good at finding other OS's installed
and configuring them
it even gives you an option to manually do it

kali should have been auto set up

very odd that it did not ????


well that would do it
you NEED to run the cent "grub-firstboot" service in cent
that sets up the first NON root user and the timezone and location


odd
Cent will AUTO set up a LVM if you do nothing

PS.
keep in mind the uid's
Debian starts at 1000
RHEL/cent starts at 500
reformat and reinstall
and this tome finish the first boot

Thanks for the replies. I was in fact in a hurry and not paying much attention during the install and yes the boot folder is totally empty so I guess yeah it didn't install at all haha. Kali is working fine which scares me to try and install it again and have the same thing happen but I do know the fix this time so meh, I'll give it a shot. I need a RHEL type distro for class and it was suggested to use this one, I've used Debian exclusively up to now

2 drives 2 os'es try changing boot order of drives maybe grub installed to 2nd drive.

Okay so I reinstalled Centos, it wasn't in grub, in Kali it appeared to have an empty boot folder again. In frustration and thinking I had a broken disc, decided to use Fedora instead and found they had a security build which was awesome. Installed, same thing. Now I was really ready to give up in anger and go back to using 2 debian distros. After extensive research and complicated commands to try and "recover boot images" turned out in the end I needed 2 commands. TWO. os-prober then update-grub. I saw that it saw the OS and updated my grub, rebooted, lo and behold I am in my Fedora now. All's well that ends well though, I'm happier with this Fedora build than I probably would've been with CentOS. Pentesting distros make me smile, especially awesome ones with great security features as well. If anyone else has this issue, it is fixable with 2 commands, don't freak out and reinstall everything a thousand times like me.