here's my problem: I have an old 500GB HDD drive from one of my old laptops which I connected to my Pi via USB. First issue: Every time I plug in the device, the Pi reboots. I already read this is due to some issue with the power supply and it's not really bothering me since I inteded to leave the HDD connected to the Pi anyways. BUT

Second issue: The HDD refuses to show up in /dev, therefore I can't mount it! It works perfectly fine on my desktop PC (where I also formatted it with ext4) but it won't work at all on the Pi.

Maybe those to issues are somehow connected to each other?! Help very welcome...

Filesystems on the pi are:

 Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk0p1            4096      147455       71680    c  W95 FAT32 (LBA)
/dev/mmcblk0p2          151552    31504383    15676416   83  Linux

output of lsusb is

Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.

output of lsblk is

zram0       254:0    0  10M  0 disk 
mmcblk0     179:0    0  15G  0 disk 
|-mmcblk0p1 179:1    0  70M  0 part /boot
`-mmcblk0p2 179:2    0  15G  0 part /

Formatting the external HDD with FAT32 doesn't work either


  • 1
    Lets start with the basics. What filesystem are we talking about? In addition what sort of partition are we talking about ( MBR or GPT )?
    – Ramhound
    Oct 8, 2013 at 17:12
  • What makes you think it is not detected? Could you post the output of lsusb and lsblk?
    – terdon
    Oct 8, 2013 at 17:15
  • Does the HDD work when you plug into another device via USB (like a PC)? Oct 8, 2013 at 17:17
  • @techie007 yes, the OP mentions it works on his desktop PC.
    – terdon
    Oct 8, 2013 at 17:18
  • 4
    If the hdd is directly powered by USB, forget about filesystem format. The RaspberryPi cannot really output enough power to spin up the hdd, probably causes a voltage drop when plugged in thus the reboot. The hdd may not get enough power to keep itself in normal operation, so the USB device won't even let the host detect it.
    – Alvin Wong
    Oct 8, 2013 at 18:03

2 Answers 2


Possible reasons why a USB hard drive doesn't show up in /dev when connected:

  • Drivers for your USB chipset or hardware not loaded or not working properly (try updating kernel if possible)
  • USB driver had a problem initializing the device - typically wrong driver, defective or unsupported hardware
  • Some hardware may act bad if too much power is consumed by attached USB devices
  • Hard drive is dead, defective or not communicating with the SATA/IDE to USB bridge (hard drive not connected to enclosure properly?) - SATA/IDE to USB bridge may also be dead or defective.
  • Hard drive is not powered on or not getting enough power
  • Physical issue with USB cable or port

Try putting the hard drive in an enclosure that is separately powered and see if you have better luck with that.

  • 1
    Will get an externally powered USB hub...
    – fpnick
    Oct 9, 2013 at 10:39
  • 2
    The HUB arrived today and it works perfectly fine now. Thanks!
    – fpnick
    Oct 17, 2013 at 18:17

You are right 400ma is not enough for Raspberry to feed the external drive. I had a similar problem and solved it by attaching a powered USB hub, and voila!! disk recognized and mounted.

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