How to resolve a boot issue after running an Ubuntu recovery on the operating system

How to resolve a boot issue after running an Ubuntu recovery on the operating system

The following article provides information about a problem with booting to the opeating system after running the Ubuntu operating system recovery tool on Dell notebooks.


At the recovery stage, the primary hard drive would normally be expected to be assigned as /dev/sda to proceed with system recovery.

However in some cases the Realtek RTS5170 card reader will accidentally report the card reader as /dev/sda, ahead of the real hard drive.

When this occurs the primary hard drive will be assigned as /dev/sdb instead.

This means that the next time you reboot the system after recovery has finished, the boot manager will be looking for the primary hard drive in the wrong location, as the primary hard drive will have shifted to /dev/sda. The boot manager entry change will make it so that system will not boot up and will stop at the screen shown below :

Gave up waiting for root device. Common problem :
- Boot args (cat /proc/cmdline)
- Check rootdelay: (did the system wait long enough?)
- Check root: (did the system wait for the right device?)
- Missing modules (cat /proc/modules: ls /dev)
ALERT! /dev/disk/by-uuid/e279d132-d5b4-42a6-932f-225b4be3f0c8 does not exist. Dropping to a shell!

BusyBox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built in shell (ash)
Enter 'help' for a list of built-in-commands.

(initramfs) _


  1. Download the latest Ubuntu LTS image from External Link

  2. Create a bootable USB stick or DVD with the Dell Ubuntu image.

    • Burning a bootable Ubuntu DVD on a working Windows PC (Windows 7 / 8)::

      1. Right click on the downloaded ISO image and select Open with > Windows Disc Image Burner.

      2. Select the location of your DVD-RW drive and choose Burn. (I recommend you check the Verify disc after burning option, it will confirm the image has been burned correctly.)

    • Burning a bootable Ubuntu USB stick on a working Windows PC (Windows 7 / 8):

      1. Download a USB installer such as Pen Drive Linux's USB Installer. External Link

      2. For this particular installer - select Ubuntu from the drop down list.

      3. Click Browse and open the downloaded ISO image.

      4. Choose the USB drive and click Create.

  3. Boot the system from either the USB stick or the DVD you've created. You may need to press rapidly on the F12 key at the Dell logo screen when you power the system on - in order to bring up onscreen a boot device selection menu. (Choose the option that matches the media you are using.)

  4. Choose the Try Ubuntu without installing option from the media's boot menu.

  5. This will boot you into a desktop, but has not installed anything on your hard drive. Whilst on the desktop press the Ctrl+Alt+T keys together to open a terminal window. Follow the steps below to resolve the boot location problem:

    1. Change to root.

      sudo –s
    2. Remount the cdrom to set it read-write.

      mount –n –o remount, rw /cdrom/
    3. Enter the command.

      cd /cdfrom/factory
    4. Edit the /cdrom/factory/common.cfg file using either the vi or gedit editors. Change the original command to set options="boot=casper automatic-ubiquity noprompt quiet splash -- modprobe.blacklist=rts5139 nomodeset"

    5. Save the file, exit the editor and the terminal window and reboot the system.

  6. If the system still won't boot try the following steps:

    1. Make sure the hardware is running fine by running diagnostics.

      1. if it fails for anything, contact technical support and pass on the error message and validation code.

      2. If it passes, proceed to the next step.

    2. Run the following command in Terminal:

      ls -lah
    3. If you get anything other than drwxrwxrwt, run the following command:

      chown username:username .Xauthority
    4. If that doesn't work run:

      sudo chmod a+wt /tmp
    5. You can also try running:

      dpkg-reconfigure lightdm
    6. If none of these work, then you are looking at recovering from your system image or backup media.

Additional Information :

Note :
Software support is provided by Canonical through the following methods:
Technical Support is provided by Dell :

Quick Tips content is self-published by the Dell Support Professionals who resolve issues daily. In order to achieve a speedy publication, Quick Tips may represent only partial solutions or work-arounds that are still in development or pending further proof of successfully resolving an issue. As such Quick Tips have not been reviewed, validated or approved by Dell and should be used with appropriate caution. Dell shall not be liable for any loss, including but not limited to loss of data, loss of profit or loss of revenue, which customers may incur by following any procedure or advice set out in the Quick Tips.

Article ID: SLN295237

Last Date Modified: 04/25/2017 06:59 AM

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