An iMac has 5 green vertical bars/stripes that appear on the screen as soon the system starts booting. The OS is Yosemite (10.10.?) When I try to boot the computer normally, safe boot, or diagnostics the computer gets just beyond the Apple logo with progress bar and then restarts itself. I can successfully boot into Single User Mode without the green bars appearing.

My first question is do you know of a fix/reason for the green vertical bars?

Second question: Do you know of a way to create a backup of the drive or “Macintosh HD” volume while in Single User Mode? It would be nice if the backup was bootable but not necessary. I tried “asr” command but it had issues (“could not initialize Disk Arbitration…”) in single user mode. Can some services be started so that “asr” works?

Thank you for any help

1 Answer 1


Vertical bars/strips are usually indicative of a display malfunction. If you are also having booting problems, it is more likely GPU failure. You should take the iMac to Apple soon as it likely requires servicing.

To backup your iMac, connect an empty hard drive with enough storage to back up your iMac, then go to System Preferences > Time Machine. Turn Time Machine on, and select the disk you just connected. Allow your Mac to backup before taking it to Apple.

  • 1
    Thank you for the GPU info. I am unable to bring up a GUI, so unless Time machine has cmds that can be accessed from single user mode (unix like cmd line), i am unable to use Time machine.
    – ermSO
    Apr 20, 2015 at 19:44

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