GRUB does not detect Windows

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

• Unable to mount Windows (NTFS) filesystem due to hibernation

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):

lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
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

2. 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"

3. 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  
}

4. Run sudo update-grub and reboot.

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.

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.

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 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 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 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