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Trying to format hard drive difficulties

FyerFyer

FyerFyer

macrumors 6502
Original poster
Dec 14, 2015
370
85
Hey guys

I'm trying to format my hard drive on my Mac Pro but I keep getting error "couldn't unmount disk".

Can anyone help?

I'll attach a file of terminal in post below
[doublepost=1459651996][/doublepost]Here is my terminal list:
(Couldn't upload pic)

0 GUID PARTITION SCHEME disk0
1 EFI EFI disk0s1
2 Apple_HPS disk0s2
3 Apple_Boot disk0s3
 

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FyerFyer said:
Hey guys

I'm trying to format my hard drive on my Mac Pro but I keep getting error "couldn't unmount disk".

Can anyone help?

I'll attach a file of terminal in post below
[doublepost=1459651996][/doublepost]Here is my terminal list:
(Couldn't upload pic)

0 GUID PARTITION SCHEME disk0
1 EFI EFI disk0s1
2 Apple_HPS disk0s2
3 Apple_Boot disk0s3
Click to expand...

I am assuming you booted from the Recovery HD instead of a USB flash drive? If so, you can't format the entire disk because the Recovery HD is running from the disk you are trying to format. Try clicking Macintosh HD and click Erase.
 
you must boot from recovery mode to format your hard disk. you either hold down command r ( or option command r) doing boot, or you boot from an os x installer that you wrote on a sd card. you can't format a hard disk that you booted from
 
rigormortis said:
you must boot from recovery mode to format your hard disk. you either hold down command r ( or option command r) doing boot, or you boot from an os x installer that you wrote on a sd card. you can't format a hard disk that you booted from
Click to expand...

Option-Command-R will not work on any Mac Pro earlier than the 6,1 as none of the old ones have an EFI that is Internet Recovery bootable.
 
rigormortis said:
you must boot from recovery mode to format your hard disk. you either hold down command r ( or option command r) doing boot, or you boot from an os x installer that you wrote on a sd card. you can't format a hard disk that you booted from
Click to expand...
monkeybagel said:
I am assuming you booted from the Recovery HD instead of a USB flash drive? If so, you can't format the entire disk because the Recovery HD is running from the disk you are trying to format. Try clicking Macintosh HD and click Erase.
Click to expand...


Hey guys
Thanks for your replies.

I'm a little bit confused

I'm formatting the drive because I'm selling the computer. If recovery HD is formatted does that mean someone can recover my stuff..?
 
FyerFyer said:
Hey guys
Thanks for your replies.

I'm a little bit confused

I'm formatting the drive because I'm selling the computer. If recovery HD is formatted does that mean someone can recover my stuff..?
Click to expand...

back up to time machine first


there are two ways to secure your computer.

1) if your computer has a mechanical old school hard drive click on secure erase and set it to do more then 3 full passes

2) if your computer has a SSD hard disk drive, turn on file vault, wait for the entire disk to encrypt, then do a full pass erase once


once the hard disk is erased, reset your pram

http://thenextweb.com/lifehacks/2010/12/04/how-when-why-to-reset-the-pram-smc-on-your-mac/#gref


once the hard disk is erased, you should be okay. if you want you can do the next owner a favor and install os x for them

i found out the pram contains the last wifi network's password you connected to, so if you are ultra paranoid, its a good idea to clear the pram
 
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rigormortis said:
back up to time machine first


there are two ways to secure your computer.

1) if your computer has a mechanical old school hard drive click on secure erase and set it to do more then 3 full passes

2) if your computer has a SSD hard disk drive, turn on file vault, wait for the entire disk to encrypt, then do a full pass erase once


once the hard disk is erased, reset your pram

http://thenextweb.com/lifehacks/2010/12/04/how-when-why-to-reset-the-pram-smc-on-your-mac/#gref


once the hard disk is erased, you should be okay. if you want you can do the next owner a favor and install os x for them

i found out the pram contains the last wifi network's password you connected to, so if you are ultra paranoid, its a good idea to clear the pram
Click to expand...

Thanks for your reply

I've backed up everything into my ext hd but I'm still confused about my previous posts. Can anyone advise on these? If I only format Macintosh HD will the new user be able to restore my stuff..?
 
If you want to make sure that the drive is 100% clean, you can do so by making a bootable OS X install volume on a USB flash drive. There are many guides on how to do this. Booting from the flash drive will allow you to securely erase the entire HDD and reinstall OS X. Select the 3-pass option when erasing, which will take several hours.
 
Thanks guys

I'm gonna try and erase the Macintosh HD and see what happens
 
So I've successfully formatted the drive but it still says there is 613 mb used in 3 files..?

However the real issue now is trying to reinstall the software. I hv the original disk but it says "Mac OS X cannot be installed on this machine"aghhh

Can anyone help..?
 
Last edited:
Gjwilly said:
Which Mac? Which OS X did it used to have? And which OS X is your installer? Also, where did you get the installer?
Click to expand...

It's a Mac Pro 5.1 I think. The OS X I tried to install from a cd was snow leopard. The disk came with it.

I have downloaded a dmg of snow leopard onto my windows comp as another option. Is it possible to make an OS X usb bootdisk from a Windows computer..?
 
h9826790 said:
If you have the original disc, why don't you just boot from the disc and format HDD / install OSX from there?
Click to expand...

I tried that but it wouldn't allow it.

Atm the drive is formatted but cannot install from cd
 
FyerFyer said:
If the recovery disk is the cd then yes it won't allow it.
Click to expand...

Yes, I am talking about that CD.

So, when you boot from the disc, you can format the HDD, but can't install OS, what't the error message?

P.S. I know that your HDD is now formatted, but seems not 100%. That may be the issue. Why not try to format the whole HDD again (if you can do that via the disc).
 
I erased the disk through the "cmd r" at startup.

The cd has never been used. The cd just won't work when I boot from it. All it says is "cannot install OS X on this machine"
 
I didn't use that disc for a long time. But from memory, that disc should work like the recovery partition (CMD R). So, you can format the whole HDD at there.

In fact, the recovery partition is a part of the HDD. If you boot from that, you can format the OSX partition, but not the entire HDD.

Did you actually try to format the entire HDD again when you boot from the disc? If not, please do that.
 
FyerFyer said:
It's a Mac Pro 5.1 I think. The OS X I tried to install from a cd was snow leopard. The disk came with it.

I have downloaded a dmg of snow leopard onto my windows comp as another option. Is it possible to make an OS X usb bootdisk from a Windows computer..?
Click to expand...
thats the issue the 10.6 OS is to old to go into a 5.1 they were made in 2010 did you try Lion? it might work
 
Do you have a USB drive with at least 8GB? You can just make a bootable El Capitan partition, and boot into that to totally erase the hard drive.
 
CapnDavey said:
thats the issue the 10.6 OS is to old to go into a 5.1 they were made in 2010 did you try Lion? it might work
Click to expand...

OP said that's the disc came with his Mac Pro.

My understanding is that's the recovery disc, not the snow leopard retail disc. That disc may came with 10.6.x which works on the 5,1, but not 10.6.0 which not support the 5,1.

Unless his Mac is a 4,1 flashed to 5,1. The disc should work.

Of course, may be I am totally wrong. In that case, I agree that the 10.6 disc won't work on a 5,1.

If OP can post the picture of the disc, that will make us much easier to give out proper suggestion.
 
Last edited:
h9826790 said:
I didn't use that disc for a long time. But from memory, that disc should work like the recovery partition (CMD R). So, you can format the whole HDD at there.

In fact, the recovery partition is a part of the HDD. If you boot from that, you can format the OSX partition, but not the entire HDD.

Did you actually try to format the entire HDD again when you boot from the disc? If not, please do that.
Click to expand...

Thanks

But when I boot from the cd there is no option except installation.

I choose the language then it just says "Mac OS X can't be installed on this computer

The only way for me to format is through the disk utility menu
[doublepost=1459784633][/doublepost]
CapnDavey said:
thats the issue the 10.6 OS is to old to go into a 5.1 they were made in 2010 did you try Lion? it might work
Click to expand...

Ahhh ok I'll try that then. I'll try mountain lion or El Capitan
[doublepost=1459784689][/doublepost]
r6mile said:
Do you have a USB drive with at least 8GB? You can just make a bootable El Capitan partition, and boot into that to totally erase the hard drive.
Click to expand...
Can I make a bootable from a Windows machine as my Mac at home doesn't hv internet..?
 
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