How EFI shell can help you backup a non-bootable Mac
I hope this post will help someone in my situation who need an emergency method to backup a non-bootable Mac.
Last week, I have to deal with a MacMini (Mid 2010 with Snow Leopard installed) which worked only 5 months until it froze and gave the following error at startup:
“You need to restart your computer…”
The same black screen with “You need to restart your computer…” text appeared when I tried to boot from the Snow Leopard DVD holding the C key. Also, error appeared when I tried to boot by holding the Shift key for Safe Boot mode or Cmd+S for Single-User mode.
So I decided to extract all valuable data and send it to an Apple service. Since, I was unable to boot even from a DVD, I tried r-Studio Emergency CD Demo, which worked fine, but the demo allows only files less than 64K to be recovered.
Then I found rEFIt site and created a bootable CD. It started fine and by using the shell I found that there is a copy command that may help me save some data on an USB flash memory. Unfortunately, rEFIt site lacks any information how to use EFI shell, but finally on other sites related to Intel EFI, I found that this shell is just a DOS box. So here are some useful commands that you may use in order to backup your data from a non-bootable Mac:
1. You have to create a bootable rEFIt CD. Follow the instructions here:
2. Insert the CD and boot you Mac by holding the C key.
3. When the rEFIt boot menu appears select EFI Shell icon.
4. In the shell:
Use "map" command to list all devices. I didn't find how to list them page by page, so you will see only the end of the listing:
Use "map -r" to remap all devices and assign them a letter. For example if you want to connect a USB flash drive:
Now, you are ready to backup your files. Begin by typing "fs0:" to enter in the first drive:
Then "ls -b" to list files page pay page:
fs0 is most probably your CD. Try with "fs1:", "fs2:" until you see your internal drive as well as USB drive. You will recognize internal drive by existence of folders like "Library", "System", "Users", etc. Finally, you are ready to copy your valuable data by "cp" or "cp -r" (for folders) command. Let's suppose your internal drive is fs1 and USB drive is fs3:
fs1:
cd Users
cd <your user>
cd Desktop
mkdir fs3:\Backup
ls -b
cp somefile.zip fs3:\Backup\
This is DOS, so use "\" for paths. Of course, you will lose Mac OS X attributes such as owner, user rights, attached system information (such as Spotlight comment) and resource forks. But unless your files use resource forks (used mostly in Mac OS 9) you can safely backup using the cp command. If you need full list of EFI shell commands you can type "help" in the shell or "help cp", "help map", etc. or search for "EFI Shell commands" in Google.
Don't copy anything from your internal drive back to it. It may be damaged. Always copy from the internal drive to your external USB drive.
