When I connect my 2TB WD My Passport external USB 3.0 hard drive, Raspberry Pi reboots and fdisk -l does not list the hard drive.

I think so there is some problem with my power adaptor, what should be the rating of my power adaptor ?

Please can anyone point me to a link.

2 Answers 2


If you are connecting the HD directly, keep in mind the pi USB ports don't deliver the 2.0 standard 500 mA (plus, 3.0 devices may need up to 900 mA). I.e., you probably can't use this drive directly, you will have to use a powered hub.

The reason for the reboot is that there is a sudden voltage drop when you plug in the device. This is like yanking the power cord for a moment, restarting the system; I have a wifi dongle that does the same thing. Again, you won't have this problem via a hub.

  • I was just yesterday running a Pi B with the a 2TB My Passport USB 3 drive, and a keyboard, HDMI out, everything worked, ran it for a few hours watching video. Power supply rated 1A @ 5.25V. Based on your info, maybe it was running out of spec, but there it is ... The WD specs don't give a current requirement on the drive, but it's 2.0 compatible so I think it would need to be able to negotiate and work within the 2.0 limitations. Also, I did not attempt to plug the drive in while the Pi was powered on.
    – greggo
    Feb 16, 2015 at 20:42
  • @greggo Of course -- it's all fine until it isn't. The point is the (non +/2) pis may not even meet the USB 2.0 spec in terms of power. They are substandard in that sense, which has consequences (including the brown out when certain devices are plugged in).
    – goldilocks
    Feb 17, 2015 at 1:10

It's likely you are running a non standard linux hard drive format e.g. ext3 If this is the case it will not show up when booted. You will need to install ntfs-3g so that it can read the drive.

  • 1
    fdisk -l will list all partitions including NTFS even if ntfs-3g is not installed. It is a power issue which is causing the problem.
    – vedarthk
    Jan 21, 2014 at 10:53
  • Indeed it is very rare that the Pi can handle external drives. Out of interest do you know if the same happens for a SSD?
    – munkee
    Jan 21, 2014 at 13:04
  • I don't have external SSD drive. When I attach external drives with external power supply they work fine.
    – vedarthk
    Jan 22, 2014 at 8:40
  • OK no problem. I would assume the pi wouldn't trally benefit speed wise from a SSD anyway as its usually processing power and ram that bottlenecks speed on it
    – munkee
    Jan 22, 2014 at 12:52

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