After mounting an exrenal hdd that is formatted as hfs journalled( with help of a post on this website). Can a dmg file downloaded from the net be installed to install mac osx on the external usb drive. My MBP only responds only in single user mode or the windows partition. It has mountain lion installed as an upgrade over snow leopard. Help will be appreciated.

1 Answer 1


You should use single user mode to delete the Mac partition (see the fdisk command).

Then, you should be able to download the installer over wifi (Hold down Cmd-R upon startup).

  • Hi Douglas,Thanks for your response. On deleting the MAC Partition will my MBP boot through the recovery partition? It is not booting through this when I press alt at startup I get the three options 1. Mac. 2. Windows and 3. Recovery. On selecting recovery it keeps on restarting. Any way I will first copy my Mac os drive trhough terminal and then delete it and try Fdisk as you say.
    – Karanbir
    Oct 27, 2014 at 9:07
  • My best guess is you should choose Mac, and then hold down Cmd-R immediately afterward. We assume the Recovery partition is lost, and if nothing is found on the disk then the Mac should offer a choice to connect to the internet via wifi to download a recovery bootloader. Oct 27, 2014 at 20:56
  • I have got the macosx volume on the external usb drive using a drive dock. How do i delete only the macosx throgh the terminal.
    – Karanbir
    Oct 27, 2014 at 21:00
  • 1
    I managed to get the data off the drive with all the help from the web. I had an install CD of snow leopard. With disk utility on this DVD erased the Macos x partition zeroed it and installed the system. Getting the data from the external drive will be taken up now. Have checked it it has all the folders and files. Thanks for all the support. Recovery through the network did not work had to use the DVD install.
    – Karanbir
    Oct 29, 2014 at 4:47

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .