I have finally installed Ubuntu on my second drive. When I start my computer GRUB only offers me to boot Ubuntu, not Windows 7. What needs to be done so that I can choose between Ubuntu and Windows in GRUB?

When I press F12 for boot menu at startup and I choose Windows Boot Manager it boots into Windows 7.

I ran command sudo fdisk -l and here is log (http://pastebin.com/Cgv1igHc):

WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0xc3ffc3ff

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1  1953525167   976762583+  ee  GPT
Partition 1 does not start on physical sector boundary.
  • Please indicate your Boot-Info URL. This will provide relevant information to help you.
    – LovinBuntu
    Oct 9, 2012 at 9:30
  • 1
    For me, I was getting this warning Warning: os-prober will not be executed to detect other bootable partitions. after running sudo update-grub, so I fixed by doing this
    – WiseTap
    Sep 18, 2022 at 18:27

13 Answers 13

  1. Boot Ubuntu and mount your Windows partition (simply open the disk on Nautilus)

  2. Run the following on the command line (Ctrl+Alt+t):

    sudo os-prober
  3. If your Windows installation was found, you can run:

    sudo update-grub

Note that step 2 is just for your convenience. You could just mount the Windows 7 partition and then run update-grub.

Related question

  • 2
    I have 2 partitions with 2 windows install, it only detects my install on another partition, but not the new installed windows (on a SSD)! even mounted... an idea? May 29, 2015 at 9:00
  • Thanks. Interesting that the os-prober seems to need step 1. Very important, or windows won't work. Oct 26, 2016 at 2:03
  • mount -t ntfs-3g -o ro /dev/sda4 /media/windows to mount the windows partition May 1, 2017 at 4:23
  • Thanks. I can't explain how frustrated I was till I followed this. Mar 1, 2023 at 19:33

If the os-prober method above doesn't work try adding a custom grub menu entry. Documented here.

First two steps are for finding your <UUID>.

  1. Run lsblk and find the name of the row with /boot/efi

Example output (here the answer is sda2):

sda           8:0    0   477G  0 disk 
├─sda1        8:1    0   450M  0 part 
├─sda2        8:2    0   100M  0 part /boot/efi
├─sda3        8:3    0    16M  0 part 
├─sda4        8:4    0    47G  0 part /windows
├─sda5        8:5    0 425,6G  0 part /
└─sda6        8:6    0   3,7G  0 part [SWAP]
mmcblk0     179:0    0  14,9G  0 disk 
└─mmcblk0p1 179:1    0  14,9G  0 part
  1. Run sudo blkid /dev/sdaX where sdaX is the answer from previous step (sda2 in my case).

Example output (here the answer is 58E4-427D):

/dev/sda2: UUID="58E4-427D" TYPE="vfat" PARTLABEL="EFI system partition" PARTUUID="b81727be-ba90-5f8c-ab98-d3ec67778b7d"
  1. Add the following at the end of the file /etc/grub.d/40_custom:
menuentry "Windows 7" {  
     insmod ntfs  
     set root='(hd0,1)'  
     search --no-floppy --fs-uuid --set <UUID>
     chainloader +1  
  1. Run sudo update-grub and reboot.
  • 1
    Thanks to @Christopher Markieta for all the details in another answer. Added them to this one as well (even though the specifics of the custom entry are different.
    – Carolus
    Aug 21, 2019 at 10:19
  • @PhilippeGachoud Ubuntu 20.04 in my case is not detecting the windows drive at all, and the grub is installed on another partition on the same drive as Ubuntu!
    – Bilal
    Apr 20, 2021 at 10:23

I had Windows 10 running and then tried dual boot. Once Ubuntu was installed, Win 10 wasn't showing up in my GRUB loader. I tried the following --

First of all, I disabled Secure Boot in Win10. Then ran the below commands in Ubuntu :

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

Worked out pretty well. Was able to find both Windows and Ubuntu in GRUB after that.

  • Does this PPA still exist? I wasn't able to add it and it claimed it did not exist from Ubuntu 18.04 boot disk
    – jocull
    Aug 20, 2018 at 14:42
  • Just received a 404 Not Found error on Debian
    – winklerrr
    Apr 21, 2019 at 9:20
  • If wifi is not connected it will claim it doesn't exist. This exact URL worked for me just now
    – Winter
    Jan 8, 2020 at 0:46

I solved a similar problem following steps of Boot-Repair

Install boot-repair

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

Push "Recommended repair" And put in a terminal some commands as it suggested.

I think my Grub doesn't recognize windows due to a bad shutdown, and it solved the problem.


Slightly different method as I copied from a working example on another computer, posting for my own records.

Append the following to /etc/grub.d/40_custom:

menuentry "Windows 10" {
        insmod part_gpt
        insmod fat
        search --no-floppy --fs-uuid --set <boot_efi_uuid>
        chainloader /EFI/Microsoft/Boot/bootmgfw.efi

where <boot_efi_uuid> is the UUID of your /boot/efi partition. To find this:

$ lsblk
NAME              MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT                                                  
sda                 8:0    0 119.2G  0 disk
└─md126             9:126  0 357.7G  0 raid0
  ├─md126p1       259:0    0   499M  0 md
  ├─md126p2       259:1    0   100M  0 md    /boot/efi                                                   
$ sudo blkid | grep md126p2 # Replace with your device
/dev/md126p2: UUID=<boot_efi_uuid>

Then of course, once you're saved the file, run:

sudo update-grub

Reboot, you should now be able to successfully start up Windows.

  • 1
    Thanks! FYI, according to /etc/grub.d/README, the filename should be 10_windows (or similar).
    – Josh M.
    May 6, 2020 at 18:59
  • 1
    I had the same issue on a raid volume, with RHEL 7. I could resolve using this answer. Thanks a ton!
    – NixMan
    Dec 23, 2022 at 4:56

If you have previously had a RAID installed that may be causing issues. In my case, I built my desktop in 2010, and I installed two 1.5 TB with a striped RAID. User gracemercy54 mentions here that this is left over metadata from the former RAID configuration.

When I originally tried the steps by Hermes I got an error specifying "wrong number of devices in a RAID set." So, if this happens to you open a terminal and run:

   sudo dmraid -rE
   sudo os-prober
   sudo update-grub

That fixed this for me.

  • I think mine also caused by the raid. But sudo dmraid -rE does not work for me. I finally made it by switch to AHCI in BIOS temporary, then boot to Ubuntu and execute sudo update-grub , then switch RAID ON back.
    – realhu
    Nov 20, 2017 at 13:50
  • 3
    WARNING: this will destroy your RAID array if you are still using it. Feb 16, 2019 at 22:44

I had issues like here above and the solution was just to add manual entry as below:

menuentry "WINDOWS10 (on /dev/sda1)" --class windows --class os {
    insmod part_msdos
    insmod ntfs
    set root='(/dev/sda,msdos1)'
    search --no-floppy --fs-uuid --set=root 688EB92384B85968
    drivemap -s (hd0) ${root}
    chainloader +1

where UUID above (688E...) was taken from boot windows disk via blkid /dev/sdb1.

ATTENTION: the additional line

set root='(/dev/sda,msdos1)'

refers to sda which is visible under Ubuntu as /dev/sdb even actually it is the first disk in sata bus while /dev/sda is in fact second drive mounted as root /.

Maybe that is why grub scripts could not work properly. I had no time to change the physical order of disks but it is quite possible it would help to resolve the issue, too.


I had the same problem with Windows 10. I installed Linux Mint 18.1 Cinnamon 64-bit on my laptop for dual boot with WIN10. After the installation GRUB only offered to boot Linux but not Windows.

I found the video solution for windows 10 missing from grub menu and the forum thread Grub not recognizing Win10 after Update/Repair, but unfortunately neither worked for me so I used a combination of these two to resolve my problem.

Open your terminal and follow these commands and open the file named 40_custom:

sudo gedit /etc/grub.d/40_custom

Add these lines to the end of the file and then save and exit:

menuentry "Windows 10" {
   set root='{hd0,1}'
   chainloader + 1

After you save the file update your GRUB with this command:

sudo update-grub

Then restart your machine to see if it works.

Hope this will work for others too!

  • I believe that this answer while correct, is largely a copy of the answer submitted May 29, 2015 May 30, 2017 at 13:55

Edit: As @Guss specified, this should be configured in /etc/default/grub, not the built-in script.

Old answer:

Follow these steps if os-prober shows Windows, but GRUB does not.

  • Edit grub-mkconfig
    sudo nano /usr/bin/grub-mkconfig
  • Find these lines near the middle
    # Disable os-prober by default due to security reasons.
  • Change true to false
  • Exit nano (CTRL+X, Y, Enter)
  • Update GRUB
    sudo update-grub
  • With current Ubuntu LTS, you can add GRUB_DISABLE_OS_PROBER=false to the /etc/default/grub file - which is a configuration file and won't be overwritten by an update.
    – Guss
    Jan 14, 2023 at 23:22

I had the same problem and had spent 2 days figuring it out. But today I had this sudden idea in the morning and it worked out.

You should review your bios/uefi settings. In my case I had to let Uefi boot first. Otherwise I wasn't able to detect windows from ubuntu. What I had to set was ubuntu > Windows Boot Manager > DISK1 > DISK2 > DISK3. Insted DISK1 > ubuntu > Windows Boot Manager > DISK3.

I had 2 ubuntu installations one on hdd and one on ssd. Apparently ssd installation wasn't showing as UEFI for some reasone but I wanted boot faster disk first.

I wasn't expecting that order of boot can influence grub in detecting systems. So it is worth to review that.


I had the same issue after I installed the updates from ubuntu. The following commands worked for me perfectly:

sudo apt-get install os-prober

First install os-prober to detect windows and then update grub:

sudo grub-mkconfig -o /boot/grub/grub.cfg
  • 1
    Confirmed: "os-prober" was missing. This time Linux Mint 19.3 Tricia. No error messages while running "update-grub" about missing os-prober, just failed to detect existing Windows partition.
    – ajaaskel
    Mar 28, 2020 at 17:09

In addition to the answer of Bartosz Dabrowski, which lead me to solving my problem:

Be sure that if your Linux uses UEFI Boot/GPT that your other OS (eg. Windows in my case) also uses UEFI Boot/GPT. Coming from an old Win7 to Win10 installation the hard drive still had old school boot and MBR. Somehow os-prober and boot-repair had their problems to fix this.

Ensure that in BIOS / Boot order there is your HDD with ubuntu (eg. uefi: ubuntu) and your HDD with Windows Boot Manager (eg. uefi: Windows Boot Manager) to be found.

If WBM is missing ensure that windows boot disk has GPT. You can check this in Windows using Disk Management (Win + X, then Disk Management).

There is a Windows tool: mbr2gpt which can convert your MBR to GPT. After doing so (and booting via UEFI) os-prober and finally update-grub was able to find my Windows installation and added it to the boot options of grub.


Okay, so I had the same problem and couldn't find a solution for me out there for a long time, finally got it, so here is my little grain of sand to the world. Before you try, remember to check you are booting using UEFI everytime you can:

Apparently, in the process of installing Debian the Windows data inside the EFI partition was lost, so what I did is a System restore using a Windows 10 USB (I tried fixing the boot but somehow it didn't work, I even tried it on console, anyways I lost no data). After this, now I coulnd't boot Debian, so I run a Debian live CD, mounted everything and chrooted like this (and don't forget to boot the USB as UEFI):

mount /dev/your_linux_partition /mnt
cd /mnt
mount -t proc /proc proc/
mount -t sysfs /sys sys/
mount --rbind /dev dev/
mount --rbind /sys/firmware/efi/efivars sys/firmware/efi/efivars/
mount /dev/your_efi_partition /boot/efi/
chroot /mnt /bin/bash

Now, here os-prober didn't detect Windows 10, but I decided to grub-install /dev/sda and grub-update anyways and restart.

Here is the funny thing, now I couldn't boot Windows 10 and only Debian, BUT!, I tried once again to grub-update and finally found the Windows 10 boot. This doesn't make any sense honestly, but I don't care. Hope it helps anyone as desperate as me :D .

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