I was recently trying to pull data off of an iMac for a friend, but didn’t have any Macs around with FireWire ports to get at the iMac HD in target disk mode1. This method does require an external hard drive.
Start up your Mac in single-user mode2, then run the following commands3:
# Check the filesystem $ /sbin/fsck -y # Mount the root volume $ mount -uw / # Create mount destination $ mkdir /Volumes/backup # Get a list of available drives $ df -h # Plug in USB backup drive, look for new drive name $ df -h # Mount the drive with the name you got from last step. Probably looks # something like /dev/rdisk2s2. Note the rdisk / disk name difference. $ mount -t hfs /dev/disk2s2 /Volumes/backup # rsync data to your backup $ rsync -ahz /Users/you/ /Volumes/backup/
1Share files between two computers with target disk mode: https://support.apple.com/en-us/HT201462
2How to start up your Mac in single-user or verbose mode: https://support.apple.com/en-us/HT201573
3Mount USB Memory Sticks in single user mode: http://hints.macworld.com/article.php?story=20030714194313542