I have a Raspberry Pi 3+ and I boot Raspbian on an SD card sold with the Raspberry Pi 3+, I specify that the SD card was therefore already flash when purchased.

For a few weeks I had planned to make myself a NAS server with my own Python server and React application and stored all the data from my NAS on an external hard drive connected by USB to the Raspberry Pi 3+.

The problem is that if the hard disk is plugged in, the Raspberry Pi 3+ always wants to boot from the hard disk and not the SD card, which creates a big problem because there is no flash on the hard drive and it throws a console error on boot to say it can't find a boot.

Here is the error obtained when switching on with the external hard drive connected:

error 110 whilst initializing sd card

Priorities are supposed to be SD Card > USB, so I don't understand why it insists so much on connecting to the HDD and not the SD Card, also when I remove the HD from the RPi it boots normally to the SD Card and there is no problem.

I looked everywhere for a solution to this to change the boot order of the RPi but I can only find answers to do the opposite: boot an RPi from a USB flash drive, I also tried to mount the HD but the 'OS returns me that it is already mounted.

So I would like to understand what I have to change, if there is a solution that works with this OS? because I don't want an OS for NAS servers, I really want to do it myself and keep my current environment.

  • @Greenonline Thank you for your answer ! I already tried this option, in raspi-config the boot options are limited to console or GUI display... I also looked at the advanced options and couldn't find anything to set priorities or find them I also can't update the tool to manage the configuration because I get an error trying that. what happens is that once the hard drive is connected, when booting I get this error: error 110 whilst initializing sd card
    – Naikho
    Jul 25 at 16:14
  • Have you tried echo program_usb_boot_mode=0 | sudo tee -a /boot/config.txt followed by a reboot? This should get written to the internal firmware on the reboot. Also, as you can assume, =1 turns it on. Also, I am not blindly giving you info from a website. I use it. Jul 25 at 16:20
  • 1
    This is a decent question, but I edited it because the title wasn’t clear and the error should have been placed in context in existing text. Also bolding every few words at the beginning is really unnecessary; the details are very clear. No need to bold those items. Jul 25 at 16:21
  • Please edit your question to state exactly what you have tried, in order to save people from suggesting solutions that you have already tried. Jul 25 at 16:21

1 Answer 1


My microSD card was simply dead. I changed it after multiple tests which showed that it was an error of the card and not of the hard disk.

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    Jul 25 at 20:34

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