Windows 10 missing from grub after Ubuntu update

Question

So I updated Ubuntu to 14.04 a few days ago and I just noticed Windows 10 went missing from the grub menu options. I tried multiple variations of update-grub and tried using boot-repair, too, but nothing fixed it. Here's the pastebin from boot-repair.

I'm at a loss as to what to try next. Any help?

EDIT: After reading a few suggestions elsewhere, I tried editing /etc/grub.b/40_common, and here are its current contents:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply     type the
# menu entries you want to add after this comment.  Be careful not to     change
# the 'exec tail' line above.
menuentry "Windows 10" {
    set root='(hd0,msdos1)'
    chainloader +1
}
menuentry "Windows 102" {
    set root='(hd0,msdos2)'
    chainloader +1
}

But booting from either "Windows 10x" option doesn't work.

Option 1 (set root='(hd0,msdos1)') displays this error (imgur .com/AbymY1r.jpg), which stays onscreen for about half a minute or until I ctrl+alt+del out of it (which restarts the computer and goes back to grub).

Option 2, on the other hand, gives off this error:

BOOTMGR is missing
Press Ctrl+Alt+Del do restart

I tried using the repair options through the Windows 10 installation disk, and assorted commands within it (e.g. bootrec /RebuildBcd, bootrec /FixMbr and bootrec /FixBoot), but all that did was screw up grub again, and I ended up not being able to boot to neither Ubuntu nor Windows. I made grub come back by using the Ubuntu Live CD, now I'm back to the same problem, except for these new Windows 10 entries I manually added to grub.

This is the output for fsbkl -f:

NAME   FSTYPE LABEL           MOUNTPOINT
sda                           
├─sda1 ntfs   System Reserved 
├─sda2 ntfs                   
├─sda3                        
├─sda5 swap                   [SWAP]
└─sda6 ext4                   /
sr0

EDIT 2: SOLVED!

So, I managed to solve it by following Christian_Sosa's answer at MS support, basically run chkdsk on the windows drives and then try startup repair. In my case, chkdsk did the trick.

Answer 1

I also had the same problem while updating Ubuntu from 12.04 to 14.04.
Boot Ubuntu from a live USB/CD and install Boot Repair

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo sed 's/trusty/saucy/g' -i /etc/apt/sources.list.d/yannubuntu-boot-repair-trusty.list
sudo apt-get update
sudo apt-get install -y boot-repair && (boot-repair &)

If it doesn't gets repaired automatically by boot-repair, then you may try it again and at the end of the process play with "Advanced options".

Answer 2

So, I managed to solve it by following Christian_Sosa's answer at MS support, basically run chkdsk on the windows drives and then try startup repair. In my case, chkdsk did the trick.

1. Boot "Repair" mode from a Windows 10 install disk.
2. Launch the command prompt

3. Type the following commands:

   • diskpart

     This will launch the disk partition utility, we will want to know the volume disk letter for where our OS is located.

   • list volume

     It should list your HDD as well as their drive letter. Remember the drive letter that is in a HDD that most resembles the storage capacity. It may or may not say "boot" for file description.

In my case, I had to repeat this process both for C: and D: drives, though both had very different sizes.

• exit

  In order to run the next command we will need to exit the disk partition utility.

• chkdsk /f X:

  replace X for your boot os drive letter that we confirmed earlier.

  4. Reboot the system back into the Recovery disc.
  5. Choose Startup Repair and let it run.

In my case, Startup repair never actually ran, but I tried anyway. It seems chkdsk alone did the trick. And for the record, the correct grub menuentry in my case was

menuentry "Windows 10" {
  set root='(hd0,msdos1)'
  chainloader +1
}

Thanks for the answers and comments.