My main Macintosh HD partition just disappeared

Hello there

I was trying to install Ubuntu Linux alongside Mac OS X by following a popular tutorial on the internet but I seem to have screwed things up when I tried to do it manually by choosing "Something Else" in the installation settings; the reason is because the installation could not detect that Mac OS X was actually installed and so things had to be done manually.

I originally shrunk the Macintosh HD partition and was going to use the free space for Ubuntu, but I don't remember exactly what went wrong but now I can no longer even see the Macintosh HD partition any longer (which seems to be called UNTITLED in Disk Utility). The problem is that I did not perform a backup as I thought the procedure was very simple and I had already done it on my PC earlier, but turns out I was dead wrong again. Now I seem to have lost my data and was wondering if there is anything I could do to make it work.

Whenever I try to create, delete, or modify a partition in Disk Utility, the operation just immediately fails. At first I thought it was because of FileVault so I turned it off from Terminal but then it just says 'operation failed'.

Any ideas are much appreciated.

UPDATE: I tried the following commands in Terminal in order to try and mount the partition to no avail.

sudo asr adjust --target /dev/disk0s2 --settype "Apple_HFS"

diskutil mount readOnly /dev/disk0s2

Terminal just says asr: Volume adjustment failed: Invalid argument.

If it is indeed wiped about the only thing you can do is boot to Recovery (Cmd-R or Option at boot) and reinstall the system.
Did you ever make an install USB stick? Would make things easier.
I'm Afraid your data is gone.

Thank you for your reply, cradom. I'm currently attempting to make a bootable USB drive from my PC since I have an old backup of my MacBook which contains Mac OS X El Capitan. I'm using an application called TransMac in order to do so. I used the Internet Recovery option last night but I was unable to do just about anything in Disk Utility, and I'm guessing because Internet Recovery is technically running from within the hard drive? I am hoping I'll be able to wipe the whole hard drive and repartition it when installing Mac through USB.

Just make SURE it's bootable before you do anything. Not familiar with TransMac so be careful.

Won't work alas from yur PC. What version OS X was on the computer? Suggest you go into Recovery Mode and download the OS.