2011 iMac replaced hard drive now unable to mount

[twr7cx]

Evening all, apologies in advance for the picture heavy post but I believe that they will add value to explaining the issue that I am currently experiencing.


I have a 2011 iMac 27" in which the original hard drive failed (not too bad after 7 years). I purchased the OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade < https://eshop.macsales.com/item/OWC/DIDIMACHDD11/ > and a Samsung 850 EVO 250GB SSD hard drive to install. I tried to SuperDuper from an another computer to it first but it failed so I progressed with the installation figuring I would be able to erase it and reinstall from Internet Recovery. Followed the guides and no problems with the physical installation.


I've turned the computer on and upon detecting that it didn't have a startup disc with MacOS installed, it has entered macOS Utilities. I've connected it to the wifi and tried to Reinstall macOS but was unable to see the disc to instal High Sierra on:


[URL='https://i.imgur.com/0SuatTy.jpg%5b/img']https://i.imgur.com/0SuatTy.jpg[/img[/URL]]

https://imgur.com/0SuatTy


So I went into Disc Utility thinking I will need to Initialise the disc or some such. It shows there but is having difficulties and seems to be due to being unable to be mount disk0s2 part:


First Aid:


[img][URL='https://i.imgur.com/qUyPNOA.jpg%5b/img']https://i.imgur.com/qUyPNOA.jpg[/img[/URL]]

[URL]https://imgur.com/qUyPNOA[/URL]


[img][URL='https://i.imgur.com/6oRCiRa.jpg%5b/img']https://i.imgur.com/6oRCiRa.jpg[/img[/URL]]

[URL]https://imgur.com/6oRCiRa[/URL]


Partition:


[img][URL='https://i.imgur.com/6UqBPb8.jpg%5b/img']https://i.imgur.com/6UqBPb8.jpg[/img[/URL]]

[URL]https://imgur.com/6UqBPb8[/URL]


Erase:


[img][URL='https://i.imgur.com/uq3FpDF.jpg%5b/img']https://i.imgur.com/uq3FpDF.jpg[/img[/URL]]

https://imgur.com/uq3FpDF


[img][URL='https://i.imgur.com/8z0j100.jpg%5b/img']https://i.imgur.com/8z0j100.jpg[/img[/URL]]

https://imgur.com/8z0j100


This is what Disk Info shows:


[img][URL='https://i.imgur.com/mgiWgnh.jpg%5b/img']https://i.imgur.com/mgiWgnh.jpg[/img[/URL]]

[URL]https://imgur.com/mgiWgnh[/URL]


[img][URL='https://i.imgur.com/GxqJTlS.jpg%5b/img']https://i.imgur.com/GxqJTlS.jpg[/img[/URL]]

[URL]https://imgur.com/GxqJTlS[/URL]


And Terminal diskutil list command shows:


[img][URL='https://i.imgur.com/l4TmxhO.jpg%5b/img']https://i.imgur.com/l4TmxhO.jpg[/img[/URL]]

[URL]https://imgur.com/l4TmxhO[/URL]


Any advice for resolving? I assume I need to force mount it using some sort of Terminal command and then erase to be able to start fresh. Anyone able to please assist in advising what the command would be?
[doublepost=1525170855][/doublepost]I tried entering in Terminal the following:

diskutil unmount /dev/disk0s2

and recieved back:

disk0s2 was already unmounted

so I entered:

diskutil mount /dev/disk0s2

and received the following error:

Volume on disk0s2 failed to mount
If the volume is damaged, try the "readOnly" option

Not sure how to do readOnly option but I don't think that would allow me to erase it...

 

[twr7cx]

I ended up using SuperDuper app to back up my laptops HDD to a Seagate external USB3 HDD. I then plugged this into the iMac and booted off it. I was then able to use Disk Utility to Erase the HDD. At this point I could have done a fresh installation of MacOS, but instead chose to use SuperDuper to copy the external HDD to the iMacs internal so that its all set up and ready to go the way I want it. The process is currently running.