I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.

How can I get Ubuntu back?

  • I think it is a common task, I also have two HDDs, and Ubuntu+Windows. I hope you can repair it with the right way. Try to follow this tutorial. Any questions, ask me! – antivirtel Dec 17 '11 at 7:24
  • 1
    Related (when GRUB was installed to the wrong drive's MBR): Grub rescue problem after installing ubuntu – Eliah Kagan Jan 21 '13 at 4:20
  • Yes you can, you would just have to do a normal boot and install with windows and then it should show up in the Grub boot menu at the start-up of the computer. – Rampoo1208 Jul 30 '13 at 18:51
  • I know this is an old thread but I fixed the problem by changing the boot mode in the bios from UEFI to Legacy. – user183708 Aug 13 '13 at 11:32
  • 1
    NOTE: the accepted answer is a general instruction on how to repair grub. It is also applicable to the wide variety of circumstances when GRUB is written incorrectly by the installer (ubiquity). – Danatela May 14 '14 at 5:14

12 Answers 12

up vote 321 down vote accepted

When you install Windows, Windows assumes it is the only operating system (OS) on the machine, or at least it does not account for Linux. So it replaces GRUB with its own boot loader. What you have to do is replace the Windows boot loader with GRUB. I've seen various instructions for replacing GRUB by mucking around with GRUB commands or some such, but to me the easiest way is to simply chroot into your install and run update-grub. chroot is great because it allows you to work on your actual install, instead of trying to redirect things here and there. It is really clean.

Here's how:

  1. Boot from the live CD or live USB, in "Try Ubuntu" mode.
  2. Determine the partition number of your main partition. sudo fdisk -l, sudo blkid or GParted (which should already be installed, by default, on the live session) can help you here. I'm going to assume in this answer that it's /dev/sda2, but make sure you use the correct partition number for your system!

    If your main partition is in an LVM, the device will instead be located in /dev/mapper/, most likely, /dev/mapper/{volume}--{os}-root where {volume} is the LVM volume name and {os} is the operating system. Execute ls /dev/mapper for the exact name.

  3. Mount your partition:

    sudo mount /dev/sda2 /mnt  #Replace sda2 with the partition from step 2
    

    If you have a separate /boot, /var or /usr partitions, repeat steps 2 and 3 to mount these partitions to /mnt/boot, /mnt/var and /mnt/usr respectively. For example,

    sudo mount /dev/sdXW /mnt/boot
    sudo mount /dev/sdXY /mnt/var
    sudo mount /dev/sdXZ /mnt/usr
    

    replacing sdXW, sdXY, and sdXZ with the respective partition numbers.

  4. Bind mount some other necessary stuff:

    for i in /sys /proc /run /dev; do sudo mount --bind "$i" "/mnt$i"; done
    
  5. If Ubuntu is installed in EFI mode (see this answer if you're unsure), use sudo fdisk -l | grep -i efi or GParted to find your EFI partition. It will have a label of EFI. Mount this partition, replacing sdXY with the actual partition number for your system:

    sudo mount /dev/sdXY /mnt/boot/efi
    
  6. chroot into your Ubuntu install:

    sudo chroot /mnt
    
  7. At this point, you're in your install, not the live session, and running as root. Update grub:

    update-grub
    

    If you get errors or if going up to step 7 didn't fix your problem, go to step 8. (Otherwise, it is optional.)

  8. Depending on your situation, you might have to reinstall grub:

    grub-install /dev/sda
    update-grub # In order to find and add windows to grub menu.
    
  9. If Ubuntu is installed in EFI mode, and EFI partition UUID has changed, you may need to update it in /etc/fstab. Compare it:

    blkid | grep -i efi
    grep -i efi /etc/fstab
    

    If current EFI partition UUID (from blkid) differs from the one in /etc/fstab, update /etc/fstab with current UUID.

  10. If everything worked without errors, then you're all set:

    exit
    sudo reboot
    
  11. At this point, you should be able to boot normally.

If you cannot boot normally, and didn't do step 8 because there were no error messages, try again with step 8.

  • Sometimes giving GRUB2 the correct configuration for your partitions is not enough, and you must actually install it (or reinstall it) to the Master Boot Record, which step 8 does. Experience helping users in chat has shown that step 8 is sometimes necessary even when no error messages are shown.
  • 1
    Comments are not for extended discussion; this conversation has been moved to chat. – Thomas Ward Apr 7 '17 at 0:43
  • I still want Windows to be my primary boot OS. Is this still the right fix? How do I choose which OS to boot to? F11? – Jeff Jul 28 '17 at 16:34
  • 1
    @ScottSeverance I saw from your profile that you live in DFW. Have you considered giving classes or live tutorials to get people deep into Linux? – Mohammed Joraid Sep 26 '17 at 1:06
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    These problems don't get old :D – Not that when dealing with EFI, you might need to install grub-efi-amd64 and if you are using secure boot you'd want to use grub-install --uefi-secure-boot. This is also detailed in superuser.com/a/376471/197980 – Raffael Dec 1 '17 at 1:12
  • 1
    This solution is applicable also for Windows 10 on computer with BIOS (i.e. not UEFI). The question about which one you have can be answered with this tip - thewindowsclub.com/check-if-uefi-or-bios. – okolnost Jun 27 at 4:20

The Windows installer doesn't care about other OS in the system. So it writes own code over the master boot record. Fortunately the solution is easy too.

You need to repair the MBR. Do the following

Boot using a live usb/cd of ubuntu. Use boot-repair to fix the problem.

After booting with live usb/cd, run following command in terminal:

sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair

Use Recomended Repair.

enter image description here

More info - https://help.ubuntu.com/community/Boot-Repair

  • 2
    you mean to say its intentional by the Microsoft people?? Also dual booting did work with windows 7 so doesn't it contradict your first line that "The windows installer doesn't care about other OS in the system." – Shagun Sodhani Sep 1 '12 at 7:04
  • Windows breaks grub all the time its a really common issue and one ive had to deal with myself. The answer is still good and should fix the problem. – damien Sep 1 '12 at 7:18
  • 5
    you have installed windows 7 first then linux. So linux recognize windows not windows recognized linux. Ttry reinstalling windows7, you will see what I meant. – Web-E Sep 1 '12 at 7:26
  • Don't do this when you have encrypted partitions (luks), it messed it up. It also reinstalls GRUB with apt-get - no idea why it's doing that. – Meng Tian Jan 5 '14 at 16:14
  • 1
    boot repair supports legacy mode very well, perhaps you need to boot the live cd/usb in legacy mode as well @fuzzyanalysis :) – Web-E Jan 1 '15 at 14:08

I never got in trouble by using these instructions:
https://wiki.ubuntu.com/Grub2#Recover

First of all, you must start your system from a live cd. Then

METHOD 3 - CHROOT

This method of installation uses the chroot command to gain access to the broken system's files. Once the chroot command is issued, the LiveCD treats the broken system's / as its own. Commands run in a chroot environment will affect the broken systems filesystems and not those of the LiveCD.

  1. Boot to the LiveCD Desktop (Ubuntu 9.10 or later). Please note that the Live CD must be the same as the system you are fixing - either 32-bit or 64-bit (if not then the chroot will fail).

  2. Open a terminal (Applications > Accessories > Terminal).

  3. Determine your normal system partition - (the switch is a lowercase "L")

    sudo fdisk -l
    

    If you aren't sure, run

    df -Th  
    

    Look for the correct disk size and ext3 or ext4 format.

  4. Mount your normal system partition:

    Substitute the correct partition: sda1, sdb5, etc.

    sudo mount /dev/sdXX /mnt  
    

    Example: sudo mount /dev/sda1 /mnt

  5. Only if you have a separate boot partition: sdYY is the /boot partition designation (for example sdb3)

    sudo mount /dev/sdYY /mnt/boot
    
  6. Mount the critical virtual filesystems:

    sudo mount --bind /dev /mnt/dev
    sudo mount --bind /dev/pts /mnt/dev/pts
    sudo mount --bind /proc /mnt/proc
    sudo mount --bind /sys /mnt/sys
    
  7. Chroot into your normal system device:

    sudo chroot /mnt
    
  8. If there is no /boot/grub/grub.cfg or it's not correct, create one using

    update-grub
    
  9. Reinstall GRUB 2:

    Substitute the correct device - sda, sdb, etc. Do not specify a partition number.

    grub-install /dev/sdX
    
  10. Verify the install (use the correct device, for example sda. Do not specify a partition):

    sudo grub-install --recheck /dev/sdX
    
  11. Exit chroot: CTRL-D on keyboard

  12. Unmount virtual filesystems:

    sudo umount /mnt/dev/pts
    sudo umount /mnt/dev
    sudo umount /mnt/proc
    sudo umount /mnt/sys
    
  13. If you mounted a separate /boot partition:

    sudo umount /mnt/boot
    
  14. Unmount the LiveCD's /usr directory:

    sudo umount /mnt/usr
    
  15. Unmount last device:

    sudo umount /mnt
    
  16. Reboot.

    sudo reboot
    
  • 7
    Just a note that it isn't necessary to worry about unmounting stuff, because the reboot will take care of that automatically. Sending umount commands wastes time. – Scott Severance Oct 1 '12 at 8:44
  • 5
    sudo umount -a should take care of them, as well. It's not a bad practice if you've got the few moments. At least reminds you of what's going on, and in some (corner/marginal) cases it can keep the reboot from stopping to warn you or wait for input. – belacqua Nov 3 '12 at 20:25
  • +1 for cautioning on the separated /boot partition. – qed Mar 19 '13 at 15:27
  • I've done this several times on different systems and agree that the results speak for themselves (although I too skip the umount). – Elder Geek Feb 25 '15 at 14:32

Boot from a live Ubuntu USB pendrive or CD and
Install Boot-Repair on ubuntu by following steps

Open the terminal and run the following commands

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install boot-repair

After completing the installation you can launch it from System->Administration->Boot-Repair menu if you use Gnome, or search "boot-repair" in the dash if you use Unity. Then follow the following screenshots:

Method 1

  • Click on the advanced options

Initial screen

  • Tick the options shown below

advanced option

  • Change the tab to Grub Location Tab and Tick The options Shown in the figure

enter image description here

Press Apply and Reboot the system

Method 2

  • Select the recommended Boot repair options as shown in the first screenshot

Documentation :

  • Web-E already gave this answer. Maybe improve that one instead? I left a comment on why it didn't work. – Dan Dascalescu Feb 2 '16 at 16:59
  • 1
    This method worked for me after a particularly nasty case of a Windows 10 update overwriting GRUB and then breaking its own boot loader. Following this procedure got both Windows and Linux back. In my case it was Linux Mint 18.1, and the boot-repair menus looked slightly different, but it all worked fine. Thanks! – TheBigH May 28 '17 at 22:53

Just install easyBCD in Windows 7 and do

Add New Entry > Linux/BSD > (select ) Grub2 > (push) Add Entry

Then you can choose Ubuntu on the Windows 7 bootloader to go to Grub2 (previous bootloader).

  • 3
    These instructions alone do not restore the Grub Bootloader - when I tried them, they added an extra boot option in Windows which on selection, restarted my machine and then took me to a grub> prompt. So one would need further steps as to what to do next. – therobyouknow Jun 15 '14 at 20:46
  • easyBCD allowed me to add and remove boot options that I could see in both Windows Boot Loader and BIOS, but they never worked because easyBCD relies on some sort of automated magic to find Linux partitions... it didn't work when my Linux partition was on a separate harddrive. – Fuzzy Analysis Dec 30 '14 at 12:14

There is now a simpler solution:

  1. Reboot, and enter your computer's BIOS options (F2, or sometimes F11).
  2. Go to the Boot menu, and select Boot Device Priority
  3. Check if Windows Boot Manager is above the main boot drive (usually SATA HDD … or IDE HDD …). If it is, move the boot disk priority above that of Windows Boot Manager.
  4. Save your BIOS options, and exit (usually F10).

This has been tested on a Samsung Series 7 Chronos laptop dual booting Windows 8 and Ubuntu 13.10, secure boot disabled, UEFI and legacy boot enabled.

  • This ended up being the cleanest option for me. It's a few more key strokes, but hey, it works. I have a mix of Legacy and UEFI booted devices. If users are booting one OS much more than an assortment of others, this can be faster (and safer) over the long run. – Fuzzy Analysis Dec 30 '14 at 12:21
  • This worked out for me too, after Windows 10 auto-updated itself. – luis_js Mar 19 at 6:31
  • This solution worked for me when I deleted Ubuntu from windows 10. – Vikas Gupta Mar 31 at 17:31

On EFI-based systems (such as most systems that shipped with Windows 8 or later), Windows will sometimes update its boot loader or reset it to be the default boot loader. This is particularly common when re-installing the OS or performing a major system update (upgrading to the latest Windows release, for instance). Note that Windows is unlikely to actually erase any GRUB files on an EFI-based computer. Everything needed to boot Ubuntu is still in place; it's just being bypassed. In these cases, a complete re-installation of GRUB is overkill, and in fact that carries a (small) chance that it will create new problems.

Thus, instead of re-installing GRUB in these cases, I recommend resetting GRUB (or whatever boot loader or boot manager you prefer) to be the default. There are several ways to do this, including:

  • EasyUEFI -- The easiest way to adjust the boot order, if the system is booting straight to Windows, is to use EasyUEFI, which is a free (for the basic version) third-party GUI tool for managing the EFI boot order. It's pretty self-explanatory -- locate the ubuntu entry in the list of boot options and move it to the top of the list. The next time you reboot, GRUB should come up. (If you use something other than GRUB, you'll need to locate its entry.)
  • bcdedit -- The Windows bcdedit tool can be used to set GRUB to the default boot order. The command bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi, typed in an Administrator Command Prompt window, will do this; however, if your computer boots with Secure Boot active, bcdedit /set {bootmgr} path \EFI\ubuntu\shimx64.efi will be required instead. In fact, the latter command will usually work even if Secure Boot is not in use, so I'd use that command first. Note that there's a more advanced Windows shell tool that requires a slightly different syntax than I've presented, but I don't recall the details.
  • One-time boot to Ubuntu -- Most EFIs provide a built-in boot manager, accessed by hitting a function key, Esc, or Enter early in the system start process. Chances are the ubuntu entry to boot Ubuntu will show up in this boot manager menu, enabling you to boot to Ubuntu. Alternatively, you could boot to an Ubuntu emergency medium, like the installer booted in "try before installing" mode. Either way, you can then use efibootmgr to adjust the boot order:
    1. Type sudo efibootmgr to see the boot entries.
    2. Note the current BootOrder line.
    3. Locate the entry for ubuntu and note its Boot#### number.
    4. Type sudo efibootmgr -o xxxx[,yyyy,zzzz,....] to change the boot order, making xxxx the number for Ubuntu. What comes after that is most likely not very important, although I've noted that Windows seems to be likely to add itself back to the start of the boot order if it's not in the list. Thus, you should probably ensure that Windows is in the list, and it may be safest to re-order the list so that all the original entries are there, just with the ubuntu entry moved to the top of the list.
  • Firmware setup utility -- Some EFIs' setup utilities enable you to adjust the boot order. Details vary greatly from one EFI to another, so I won't go into specifics, but you could look for such an option in your setup utility.

There are other variants on these procedures, such as using bcfg in an EFI shell, using bless in macOS, using my rEFInd to do a one-time boot, etc. I'd start with EasyUEFI, though; it's likely to be the simplest solution. Sometimes Windows insists on making itself the default every time it starts up, though, and reports indicate that bcdedit may do a better job of dealing with that problem.

Note that none of the preceding applies to BIOS-mode installations; however, as most computers that shipped with Windows 8 or later boot in EFI mode, BIOS-mode installations are becoming increasingly rare, so in many cases it's better to deal with the issue in the EFI way rather than by blindly re-installing GRUB.

  • 1
    manually one-time booting into linux (fedora28 in my case) through the EFIs build-in boot manager allowed me to use efibootmgr to re-order the boot-order (as described by Rod -> thanks!) which was messed with by a win10 update. Afterwards the GRUB-bootmanager appears as it used to before the update, so I can confirm the provided solution worked for me. I could not find the basic version of EasyUEFI but only a trial version of the non-free pro-version offered. – antiplex Aug 22 at 8:31

Boot-Repair worked for me. It's very very easy to use graphical application, you do not need to use the command line, you only have to click a button :)

All the available repair options are described in the Ubuntu documentation and there is a separate page explaining how to start Boot-Repair (by creating a bootable disk or installing it in an existing Ubuntu live disk) and how to use it.

Just boot a Ubuntu live CD, install Boot-Repair and run it.

  • It would be nice if there were an easier way to get Boot Repair, though. It's faster to just set up a chroot repair than to Google around for some other tool to install. – Scott Severance Dec 18 '11 at 1:51

When GRUB is broken, the user generally does not have access to systems, so repair must be performed from a live-session (live-CD or live-USB).

There are many possible causes to a GRUB break: Windows writing on the MBR, DRM preventing GRUB from installing correctly, installer bug, hardware change... Updating GRUB as proposed initially by Scott is generally not sufficient, reinstalling GRUB as proposed by Marco is more efficient, but still there are various situations requiring other tweaks (adding options to kernel, unhiding GRUB menu, changing GRUB options, choosing the right host architecture...). Other difficulties for repairing GRUB is the use of chroot, and the choice of the right partitions /disks.

All of this has been made easy in a little graphical tool: Boot-Repair. It shall be integrated in Ubuntu 12.04 CD for easier use, but for people needing it now, there are already some distros integrating it: Ubuntu-Secured-Remix (Ubuntu CD integrating Boot-Repair), Boot-Repair-Disk (CD running Boot-Repair at start-up), ...

Hope this helps.

Windows does not see Linux formatted partitions. You need to use gparted from a liveCD and create a primary partition formatted NTFS with the boot flag.

Some have had issues if the new primary partition is after the extended partition as Windows does not always reset partition table correctly. Best to have good backups and a separate backup of partition table.

Backup partition table to text file & save to external device.

sudo sfdisk -d /dev/sda > PTsda.txt

This is only for MBR (msdos) systems. If your Ubuntu install is in GPT partition drive you can only install Windows in UEFI mode or convert drive back to MBR (msdos).

  • The new versions of sfdisk & fdisk that work with gpt partitioned drives in 16.04 or later, will also backup the gpt partitioned drives with above command. oldfred does not remember what he ate for dinner last night, so not sure what he posted back in 2013. :) – oldfred Apr 7 '17 at 13:40
  • Hi Fred when I'm cooking forgetting dinner last night is a blessing. We deleted our previous comments. – WinEunuuchs2Unix Apr 7 '17 at 14:49

Only fsck command fixed the grub-rescue screen for me.

Use Boot-Repair to boot from Live-CD, then open Terminal

Get the correct device:

sudo fdisk -l

Need to find the boot device, the boot device has * under Boot category like here:

Device     Boot   Start       End   Sectors  Size Id Type
/dev/sda1          2048   2000895   1998848  976M 82 Linux swap / Solaris
/dev/sda2  *    2000896 943716351 941715456  449G 83 Linux

Now repair the disk by using:

sudo fsck /dev/sda2

Note: /dev/sda2 is the boot device in this example.

Enter Y to fix the issues

After entering Y about 2 times, you can stop the fsck process by entering CTRL+C, because the critical part already done.

Reboot. Done.

Answers given by Scott and Web-E are good enough and have helped a lot many times. But many a times, the boot-repair tool is not able to repair grub due to problems related to i386 and amd64 platform or one where grub can't find efi directory.
What has solved my problem like more than 10 times is to manually purge the old grub installations and install a new one.

So first perform the first 6 steps from Scott's answer where you can skip the 5th step if it gives an error:

  1. Boot from the live CD or live USB, in "Try Ubuntu" mode.
  2. Determine the partition number of your main partition. sudo fdisk -l, sudo blkid or GParted (which should already be installed, by default, on the live session) can help you here. I'm going to assume in this answer that it's /dev/sda2, but make sure you use the correct partition number for your system!

    If your main partition is in an LVM, the device will instead be located in /dev/mapper/, most likely, /dev/mapper/{volume}--{os}-root where {volume} is the LVM volume name and {os} is the operating system. Execute ls /dev/mapper for the exact name.

  3. Mount your partition:

    sudo mount /dev/sda2 /mnt  #Replace sda2 with the partition from step 2
    

    If you have a separate /boot, /var or /usr partitions, repeat steps 2 and 3 to mount these partitions to /mnt/boot, /mnt/var and /mnt/usr respectively. For example,

    sudo mount /dev/sdXW /mnt/boot
    sudo mount /dev/sdXY /mnt/var
    sudo mount /dev/sdXZ /mnt/usr
    

    replacing sdXW, sdXY, and sdXZ with the respective partition numbers.

  4. Bind mount some other necessary stuff:

    for i in /sys /proc /run /dev; do sudo mount --bind "$i" "/mnt$i"; done
    
  5. If Ubuntu is installed in EFI mode ([see this answer if you're unsure][efi]), use sudo fdisk -l | grep -i efi or GParted to find your EFI partition. It will have a label of EFI. Mount this partition, replacing sdXY with the actual partition number for your system:

    sudo mount /dev/sdXY /mnt/boot/efi
    
  6. chroot into your Ubuntu install:

    sudo chroot /mnt
    

Then do these steps:

  1. Configure all the pending packages.
    sudo dpkg --configure -a
  2. Fix the broken packages.
    sudo apt install -fy
  3. Remove the current grub.
    sudo apt purge -y grub*-common grub-common:i386 shim-signed
    This may give you a warning that your device will have no bootloader and may be unable to boot the next time. Go ahead and accept it.
  4. sudo apt install -y grub-pc
    After running this command, it will ask you to point the current sdXY to install the bootloader. Find where your current OS is installed using sudo fdisk -l command. It will be labelled as Linux. Navigate that window using Tab key and select an option using Space key.
  5. If everything goes right, grub will be installed correctly. You can also do sudo grub-update for a double check.

If the problem still persists, you can read Arch's wiki to actually understand about grub to tackle many other varieties of problems. (Yes, also helps for Ubuntu!).

protected by jokerdino Dec 2 '13 at 17:55

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