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Accidently deleted Efi Partition

T

teamd

macrumors newbie
Original poster
Sep 23, 2014
20
5
Hi guys

I have a 2014 macbook pro that i installed windows using bootcamp. During the process i deleted the 200mb partition used by mac os. Since then when i try to boot mac os, it shows a loading sign and after trying to load it I get an access denied sign and it stops there. Windows boots fine.

I have installed a new instance of mavericks onto my external hard drive and i can boot properly. While there, my macbook pro ssd has 3 partitions. 1. Disk0s2 greyed out, 2. Machintosh hd, greyed out, 3. Boot camp, mounted and working fine.

I went to win and formated that existing 200 mb partition to Fat, looked at my 180gb mac os partition and it had grey stripes in storage.

I came back to external mac os install and tried to clone the efi partition of the existing install to my internal ssd, with carbon copy, it succseeded it says but it still doesn t boot, and that partition is always fat.

I tried to mount the disk0s2 partition and it dorsn t do anything. I tried to format the 200mb partition but it says it doesn t support a journaled format.

I have valuable data on my old mac install and i would like to retrieve it somehow.

I tried everything under the sun on every forum and nothing works, i keep getting busy errors or permission error while trying to mount or convert/add gpt info to my ssd.

Does anybody have any idea what can I do?

Can t thank you enough!
 
teamd said:
..any idea what I can do?
Click to expand...

Stop formatting things for a start.

You need a EFI partition to boot OSX and this partition needs to be formatted FAT. FAT doesn't support journalling so you are formatting it wrong.

It also needs to contain boot files and it needs to be marked as bootable.

Download gdisk and print your current partition scheme (you can do this from OSX or Windows it doesn't matter).
 
teamd said:
Hi guys

I have a 2014 macbook pro that i installed windows using bootcamp. During the process i deleted the 200mb partition used by mac os. Since then when i try to boot mac os, it shows a loading sign and after trying to load it I get an access denied sign and it stops there. Windows boots fine.

I have installed a new instance of mavericks onto my external hard drive and i can boot properly. While there, my macbook pro ssd has 3 partitions. 1. Disk0s2 greyed out, 2. Machintosh hd, greyed out, 3. Boot camp, mounted and working fine.

I went to win and formated that existing 200 mb partition to Fat, looked at my 180gb mac os partition and it had grey stripes in storage.

I came back to external mac os install and tried to clone the efi partition of the existing install to my internal ssd, with carbon copy, it succseeded it says but it still doesn t boot, and that partition is always fat.

I tried to mount the disk0s2 partition and it dorsn t do anything. I tried to format the 200mb partition but it says it doesn t support a journaled format.

I have valuable data on my old mac install and i would like to retrieve it somehow.

I tried everything under the sun on every forum and nothing works, i keep getting busy errors or permission error while trying to mount or convert/add gpt info to my ssd.

Does anybody have any idea what can I do?

Can t thank you enough!
Click to expand...

read this page:

https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/chown.8.html

and this page:

https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/chmod.1.html

Once you've changed the ownership of the stuff you want off the internal drive you can pull it off. After that is done I'd nuke the drive and start again just re-download OSX while your booted off the external and point the installer at the internal drive.
 
Thanks everyone. First of all the greyed out partition was not picked up by any mac os instalation as a usable drive in order to change permissions and recover the files.

It was formatted to FAT but i wasn t able to make it a bootable partitior or add the gpt info it needs. I ve tried every advice i could get my hands on, on every forum and nothing worked, I was always receiving an error of some sort, i don t even remeber which one is which, there were that many. After 3 days I gave up. A user from another forum suggested a bunch of apps to recover my files but on disk drill worked. I recovered 70% of my data an decided to format it and reinstall os.

It has been SO frustrating... I m glad it ended.

Thanks everyone for the advice.
 
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