Erasing Hard Drive on OSX, need help please :)

Space Monkey

Space Monkey

Space Monkey

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Hi guys,

As per the title, I've gone into the recovery menu on boot up (cmd + R) and then selected erase, but on the left hand column where you need to choose a hard drive to erase, I've got 4 options and all are clickable, but I've only got a single 512GB SSD, which one do I need to click to erase?

Cheers :)
 
What are the options? It really depends on how your drive is partitioned, whether you're using FileVault etc. The top option is for the entire drive if we're talking about Disk Utility, but if you've got a Windows partition then obviously you don't want to do that.

If you're just wanting to wipe the drive from scratch then the one that's a weird model number will be the right one.
 
Hi mate,

Thanks for the reply, I think I've done it now but not sure 100% as its my first Mac :eek:

The top option seemed to be the entire drive, then it had a sub folder which was named Macintosh HD, I chose this as it was the same name given in the 'About this Mac' so I assumed this would be correct? The other 2 below were smaller 1-2GB sections, so not sure if they were the hidden restore files?

I erased the HD and then reloaded the OS, and I've now updated to Yosemite, seems all ok, so hopefully I've done it correctly?

Not sure what the difference with the top 2 options are?
 
Space Monkey said:
Hi mate,

Thanks for the reply, I think I've done it now but not sure 100% as its my first Mac :eek:

The top option seemed to be the entire drive, then it had a sub folder which was named Macintosh HD, I chose this as it was the same name given in the 'About this Mac' so I assumed this would be correct? The other 2 below were smaller 1-2GB sections, so not sure if they were the hidden restore files?

I erased the HD and then reloaded the OS, and I've now updated to Yosemite, seems all ok, so hopefully I've done it correctly?

Not sure what the difference with the top 2 options are?
Click to expand...
Top one is the actual drive itself. Everything below it indented are the various volumes on that drive (partitions with file systems on them). Don't worry, you did the right thing :-) You could have selected the Macintosh HD partition, selecting the actual drive just recreates the partition again, which is what I'd have done for the sake of it anyway (additionally, I'm not sure how the recovery partition would be installed if you selected the volume, I presume the installer would be intelligent enough to sort that out).
 
When it comes to SSDs you need to erase them properly. Get yourself a copy of parted magic. It's a tool every computer owner should have in their arsenal. The maintainer charges for the download now, but you can still get older copies.

http://www.majorgeeks.com/files/details/parted_magic.html

http://partedmagic.com/secure-erase/

You boot into the live media, securely erase the disk, it'll erase EVERYTHING (so backup important stuff) and return the disk to a fresh status.
 
OhEsEcks said:
When it comes to SSDs you need to erase them properly. Get yourself a copy of parted magic. It's a tool every computer owner should have in their arsenal. The maintainer charges for the download now, but you can still get older copies.

http://www.majorgeeks.com/files/details/parted_magic.html

http://partedmagic.com/secure-erase/

You boot into the live media, securely erase the disk, it'll erase EVERYTHING (so backup important stuff) and return the disk to a fresh status.
Click to expand...

Entirely irrelevant and a waste of time in 99.9% of use cases.

And in this case for the 0.1% disk utility does secure erase anyway.
 
BunnyKillBot said:
Entirely irrelevant and a waste of time in 99.9% of use cases.
Click to expand...

Elaborate.

BunnyKillBot said:
And in this case for the 0.1% disk utility does secure erase anyway.
Click to expand...

Do you mean zero out, 7 pass and 35 pass? Those are for HDDs and shouldn't be used on SSDs. HDDs and SSDs store data differently and you shouldn't use 7 pass and especially not 35 pass since it puts unnecessary writes on the disk. To properly remove data from SSDs you need to use ATA secure erase.
 
MagicBoy said:
The Secure Erase feature is disabled on recent versions of OS X when it detects an Apple SSD to prevent unnecessary writes. Can still be forced from a Terminal session though if so desired,.
Click to expand...

Yup. The ATA secure erase method isn't just about protecting data (by erasing it securely), but protecting the drive itself (against excessive writes that would be carried out by traditional software secure erase methods like DOD and Gutmann). And the traditional software methods aren't always successful in removing sensitive data due to the way they work and the way information is stored on SSDs.

http://nvsl.ucsd.edu/index.php?path=projects/sanitize

Individual file sanitization techniques, all of which failed and left at least 10MB of a 1000MB file.
Click to expand...

Also note that drive manufacturers sometimes didn't implement secure erase methods properly for their own hardware and data was left behind.

ATA SE works at a hardware level with the controller and tells the controller to reset all storage cells to empty, including protected areas that can't be reached by traditional methods (which is why you occassionally have to put the machine to sleep to unlock the drive).
 
Thats all riveting stuff, but we aren't talking about single file sanitation here.

http://cseweb.ucsd.edu/~swanson/papers/Fast2011SecErase.pdf

We tested ATA commands for sanitizing an entire
SSD, software techniques to do the same, and software
techniques for sanitizing individual files. We find that
while most implementations of the ATA commands are
correct, others contain serious bugs that can, in some
cases, result in all the data remaining intact on the drive.
Our data shows software-based full-disk techniques are
usually, but not always, effective, and we have found evidence
that the data pattern used may impact the effectiveness
of overwriting. Single-file sanitization techniques,
however, consistently fail to remove data from the SSD.
Click to expand...

As to 'avoiding excessive writes' its simply not going to shorten the life span of the device in any meaningful way.

Regardless, none of this is relevant in 99.9% of use cases. The OP didnt even mention the word 'secure' and has said nothing to suggest he is a defence contractor with top level material already covered by an existing IT policy. Most, usually, to be sure, is an academic application of trivia and not relevant to the general population.
 
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OhEsEcks said:
When it comes to SSDs you need to erase them properly. Get yourself a copy of parted magic. It's a tool every computer owner should have in their arsenal. The maintainer charges for the download now, but you can still get older copies.

http://www.majorgeeks.com/files/details/parted_magic.html

http://partedmagic.com/secure-erase/

You boot into the live media, securely erase the disk, it'll erase EVERYTHING (so backup important stuff) and return the disk to a fresh status.
Click to expand...

This.
 
Just went and double checked on an old iMac since it's been a while.

7eVVHyL.jpg

After that prompt it'll load the OS into RAM (runs faster this way than over USB or off a CD). You should get 2 or 3 dotted lines as it loads the OS. Depends on the speed of the machine and RAM. That machine in my picture just took seven lines to load the OS off a CD into RAM. But the machine is from 2008 or 2009 and only 4 GB of pretty slow RAM. On my current Linux rig, it loads after a line and a half of yellow dots.
 
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