Grub prompt after upgrade to Ubuntu 11.04

I upgraded a couple of machines to Ubuntu 11.04, and after the reboot, they just booted up to a grub prompt.  Like this (except an older version of grub reported):

My reading seems to indicate that this happens if you upgrade from Ubuntu 10.10 which itself had been upgraded from Ubuntu 10.04, and grub was never reinstalled.

I think it is completely ridiculous that this bug made it all the way to the Ubuntu 11.04 final release — leaving the system unbootable after an upgrade is a disaster.

The easiest way to fix it is to boot from the Ubuntu 11.04 alternate install CD.  Choose the option to “Repair a broken system.”  Go through the prompts and choose which disk has your root file system.

After this, you may have the option to just reinstall grub — if so, do it, and reboot, and your system should be fine.

If that’s not an option, choose to start a recovery shell using your root filesystem and then run the commands

grub-install /dev/sda

(possibly adjusting for where your root disk is).  Then reboot and the machine should boot.

If it still doesn’t, go back to the recovery shell and see if your /boot directory is empty (aside from the “grub” directory).  This happened to me on a machine that was set up with LVM.  The /boot folder is actually stored on a different partition and you have to mount it before grub can set itself up right.  Here’s the commands…

rm -Rf /boot/*
mount /dev/sda1 /boot
grub-install /dev/sda

Of course, these may need to be adjusted depending on which disk needs grub and which partition contains /boot.  You can use the GUI partition editor on the Live CD to check.

Now, hopefully your machine can boot up.  What a mess.  :-\

Update: May 12, 2011

dzsi posts another way to recover from this situation in the comments below.  This method does not require booting from a CD.

Note that in the commands that follow, “X”, “Y”, and “Z” should be replaced with numbers/letters that represent your boot disk.

At the grub prompt, issue these commands:

set root=(hdX,Y)
linux /vmlinuz root=/dev/sdZ ro
initrd /initrd.img

Your machine should boot up.  Start a terminal and issue these commands:

sudo grub-install /dev/sdZ
sudo update-grub

This should fix grub so that you do not have any boot trouble anymore

43 thoughts on “Grub prompt after upgrade to Ubuntu 11.04”

  1. Aaron, thank you for the instructions on getting my machine back into working order. I agree completely that this kind of failure should never happen. It’s a hideous QA failure on Canonical’s part. But again, thank you for the solution, it did the trick.

  2. Had the same problem on virtual machines (KVM) with serial consoles. I thought it was some bug around those configurations. I spent almost one day hunting this and found your post afterwards when I solved it as you with grub-install. We got what we pay for with Ubuntu and lesson is: wait a while after new releases….

  3. Hm, doesn’t work for me…I get the same window as you and when entering “boot” i get “no kernel” message…
    Seems there is a problem with GRUB with every upgrade – I think I’ll have reinstall…

  4. You saved my life ! Upgrade from 10.10 (installed directly on a new laptop, so no 10.04 there) to 11.04, and same message and grub prompt like yours. I followed your instructions, and the second step (grub-install /dev/sda, update-grub) was the good step. Thanks a lot !

  5. Thanks a lot for hinting where the problem lies!!

    Altough I had to go see at Ubuntu Help how to install grub from live-cd =)

  6. Thanks.
    I recognized the possible error,
    and simply formatted the upgraded partition.
    Then booted the Live-CD (10.10) and did the install again.
    I considered just dropping Grub4Dos into the MBR,
    but then decided that Grub2 was going to be a major player,
    and I should learn to work with it.
    Besides, Grub2 allows beautiful backgrounds.

    On my “sand-box” computer, I use 6 different OS, and Grub4Dos,
    very interesting, although I don’t expect to become a real expert.

    I elected to wait for all the 11.04 problems to be resolved,
    then I’ll try installing it.
    Opps! there was another “Upgrade to 11” message box,
    which I canceled.
    Needs to wait a month or so.

    glene77is :)

  7. Hi,

    I think it is still not the easiest solution because you need a live cd. This problem occurs when you upgraded from 10.04 to 10.10 and then 11.04. So you do not have a live cd.
    What I did:
    1. When the grub is loaded and you got the above screen you type the following commands. Of course you should substitute X,Y,Z according to your system settings.

    set root=(hdX,Y)

    linux /vmlinuz root=/dev/sdZ ro

    initrd /initrd.img


    2. Your system will start, login and type the following commands into a terminal:
    sudo grub-install /dev/sdZ
    sudo update-grub

    After you reboot, your grub should work.

  8. @dzsi

    Thanks very much for the timely message on how to fix the grub boot after the Ubuntu 11.04 upgrade. I had to use it only a few hours after your post.

    As Ubuntu is installed in the first partition of the third drive of my PC, I used the following commands:

    linux /vmlinuz root=/dev/sdc1 ro
    sudo grub-install /dev/sdc

  9. Same problem, however none of these suggestions have worked for me yet. CD 11.04 not an option.

    #grub-install /dev/sda#
    only returns this
    #grub-install /dev/sda
    cp: cannot create regular file `/boot/grub/915resolution.mod’: Permission denied#

    @dysi. Tried yours too, but no success.

  10. Thank you! It took me a few tries to get the right disk/partition arguments, but my system came right back up.

    dzsi’s and Bluehaze’s comments did the trick. Thanks all!

  11. Thanks to people like you I’ll stick to Ubuntu. My laptop starts again and my headache has disappeared. By the way, it was your second solution that did the work. Thanks again !

  12. Thank you for posting this invaluable information.

    I’ve been delaying the upgrade for weeks and finally decided I would upgrade my dev server and after the reboot I saw the Grub prompt I though “oh no, not this again”.

    Your boot from CD/DVD method worked like a charm.
    One note, if you have the CD/DVD in the drive then type exit at Grub prompt. It will take you to the screen where you need to be. To complete recovery tasks.

    Thanks again.

  13. I also had the issue with the /dev/sda1. To “attempt” this from being an issue in the future, I edited the fstab and removed sda1, mounted sda1 as boot2, copied the files over, then unmounted boo2.

    so more or less the sets were as follows:

    Using live CD boot into recovery.

    nano /etc/fstab

    remove the boot drive listed there.


    mkdir boot2
    mount /dev/sda1 boot2
    cd boot2
    mv * ../boot
    cd ..
    umount boot2
    rm -rf boot2
    grub-install /dev/sda

    rebooted, in the system.

    Seemed to work well for myself, and thinking it might resolve similar issues in the future.

    great post!!


  14. Thanks so much for this, the second set of instructions worked for me on xubuntu 11.04 following a “minor” update!

  15. many thanks to OP and dzsi as this one has caught me out on every upgrade so far, and I have now stored these cmds as I expect to be caught out again at next upgrade :)

  16. This worked for me thanks a million!

    set root=(hd0,1)
    linux /vmlinuz root=/dev/sda1 ro
    initrd /initrd.img


    sudo grub-install /dev/sda
    sudo update-grub

  17. When I read:

    “Note that in the commands that follow, “X”, “Y”, and “Z” should be replaced with numbers/letters that represent your boot disk.”

    I didn’t know how to check what to know what to replace. I checked other comments and no one spoke on this either except giving what they gave.

    I tried issuing ‘ls’ and got a list of seeming possible choices for X,Y (I forgot to copy it down). Among them was hd0,1.

    By using TAB in grub I found the command ‘root’. When I entered that I got an output that showed that hd0,1 was the root. So I decided to use that.

    I still could not figure out how to choose Z. I ended up just using sda1 like others did and that worked I guess.

    set root=(hd0,1)
    linux /vmlinuz root=/dev/sda1 ro
    initrd /initrd.img

    sudo grub-install /dev/sda
    sudo update-grub

    Then when I booted I had the Unity cannot load issue. Now, I am onto troubleshooting that one!

  18. Hey Andrew,

    You can find the information about X,Y,Z over here:

    somehow I got the system to reboot but freezes at the Ubuntu logo :( You have any new findings for this?


  19. You can press Esc when you see the Ubuntu logo to reveal the bootup messages and maybe get a hint as to where your system is getting stuck.

  20. Thanks to all,

    But all the applications, browsers, softwares and setup seems to be vanished.

    Its like a new once again!

    Do i have to do something to restrore them?

  21. I am using wubi and i cant get the x and y values.
    Followig Phillip.C’s link I used ls:
    (memdisk) (hd0) (hd0,msdos2) (hd0,msdos1)

    i tried
    ls (hd0,msdos1)/
    ls (hd0,msdos1)/boot
    ls (hd0,msdos1)/boot/grub
    ls (hd0,msdos2)/
    ls (hd0,msdos2)/boot
    ls (hd0,msdos2)/boot/grub
    but only the first and 4th gave a list of files as an output, not including vmlinuz or initrd.img. the others said
    “error: file not found”

  22. got it – it seems my problem may have been entirely different. Windows moved the files from c:/ubuntu/disk/ into c:/found.000
    when i moved it back it booted up fine

  23. error: invalid magic number

    after setting root I used the prev. conf. files:
    linux /vmlinuz.old root=/dev/sda1 ro
    initrd /initrd.img.old

  24. with raid after booting to initrd ls /dev/mapper shows exact name of root partition, which can be used instead of /dev/sda1

  25. Thanks alot for the post. found it very useful

    To resolve X and Y.
    use command

    set root=(hdX,Y)

  26. Thanks a million, worked for me too.

    Note that in the terminal, you want
    sudo grub-install /dev/sda

    and not
    sudo grub-install /dev/sda1

    Even though the linux line used /dev/sdZ to correspond to /dev/sda1! Attempting to install to a partition instead of the hard-disk will create a scary warning message and probably error. Perhaps these instructions can be edited so as not to use the notation sdZ to mean two different things.

    To find out X and Y, as shekhar notes, use the command:

    Then Z seems to correspond sdaY. i.e. if root returns: hd0, 1,
    then you want
    linux /vmlinuz root=/dev/sda1 ro
    in the second line.

    Thanks a ton!

  27. this commads are not accepted my system.
    it shows unrecoganized command
    am using ubuntu 10.10 and installed grub2 and grub-customizer
    then i change the boot banground after restarting igot this probleplease help me through mail

  28. Master!!!!!

    You’ve brilliantly solved my problem… Never thank you so much you’ve saved my system!!!

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