I'm trying to install Ubuntu on my main SSD and windows on my secondary hard drive for games. After a lot of hassle with trying to preserve my original ubuntu I bend the knee to installing Ubuntu after windows. Sadly grub isn't able to find my windows on the second hard drive.

  • Fast boot is disabled
  • Secure boot is disabled
  • Os-prober returns nothing
  • Update-grub does not add my windows install
  • adding a custom entry to /etc/grub.d/40_custom results in a /bootmgr not found error

I'm at a loss, everything I could find online I've tried. My motherboard is an Asus Maximus ranger VII if that helps with certain bios settings that I need to tweak.

blkid output:

/dev/loop0: TYPE="squashfs"
/dev/loop1: TYPE="squashfs"
/dev/loop2: TYPE="squashfs"
/dev/loop3: TYPE="squashfs"
/dev/loop4: TYPE="squashfs"
/dev/loop5: TYPE="squashfs"
/dev/loop6: TYPE="squashfs"
/dev/sda1: UUID="771f3eb4-1d56-46be-a608-c63bbf6d1782" TYPE="ext4" PARTUUID="e4ef4311-01"
/dev/sdb1: PARTLABEL="Basic data partition" PARTUUID="d55691bd-0fb2-4b58-ab7e-a352a9397d59"
/dev/sdb2: UUID="A2D2-0615" TYPE="vfat" PARTLABEL="EFI system partition" PARTUUID="b65b936b-123d-44f1-85bb-9121d581e45d"
/dev/sdb3: PARTLABEL="Microsoft reserved partition" PARTUUID="3942ab5f-23b8-475b-ba3d-c08004d620f3"
/dev/sdb4: UUID="E2B2DFFAB2DFD0E1" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="e1de24ed-0031-4b83-8b35-e8c7ec87f858"

Mount partition

First ensure you've mounted your window's partition:

NAME        FSTYPE  LABEL                    SIZE MOUNTPOINT
sdb                                         14.4G 
├─sdb4      iso9660 Ubuntu 18.04 LTS amd64   1.4G /media/rick/Ubuntu 18.04 LTS amd64
├─sdb2                                         1M 
├─sdb5      ext4    casper-rw                6.4G /media/rick/casper-rw
├─sdb3      vfat    usbboot                  244M 
└─sdb1      ntfs    usbdata                  6.4G /media/rick/usbdata
sr0                                         1024M 
sda                                        931.5G 
├─sda4      ntfs    WINRETOOLS               450M 
├─sda2                                       128M 
├─sda5      ntfs    Image                   11.4G 
├─sda3      ntfs    HGST_Win10               919G /mnt/d
└─sda1      vfat    ESP                      500M 
nvme0n1                                      477G 
├─nvme0n1p5 ext4    NVMe_Ubuntu_16.0        44.6G /
├─nvme0n1p3                                   16M 
├─nvme0n1p1 ntfs                             450M 
├─nvme0n1p8 ext4    Ubuntu18.04             23.7G 
├─nvme0n1p6 swap    Linux Swap               7.9G [SWAP]
├─nvme0n1p4 ntfs    NVMe_Win10             391.2G /mnt/c
├─nvme0n1p2 vfat                              99M /boot/efi
└─nvme0n1p7 ntfs    Shared_WSL+Linux           9G /mnt/e


Make sure your 30_os-prober is marked as executable as shown below:

$ ll /etc/grub.d/30_os-prober
-rwxr-xr-x 1 root root 11736 Jun 29  2018 /etc/grub.d/30_os-prober*


Most people recommend switching from the default Intel RST to AHCI. I've found that both work however.

I did change BIOS to not reload from hard disk each boot which saved 4 seconds or so. I also changed BIOS to not read from NIC cards which saved a few seconds. BIOS POST used to take about 16 seconds and I trimmed it down to 5 seconds. Still too long I think because Dell Inspiron 17R 7720SE is only a second or two.

In BIOS make sure TPM and secure boot is turned off. Also you might want to follow boot-repair suggestion to move partition to front of disk:

$ sudo fdisk -l
Disk /dev/nvme0n1: 477 GiB, 512110190592 bytes, 1000215216 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 43583516-680C-4323-A4B1-592DF4DEEB70

Device              Start        End   Sectors   Size Type
/dev/nvme0n1p1       2048     923647    921600   450M Windows recovery environment
/dev/nvme0n1p2     923648    1126399    202752    99M EFI System
/dev/nvme0n1p3    1126400    1159167     32768    16M Microsoft reserved
/dev/nvme0n1p4    1159168  762818491 761659324 363.2G Microsoft basic data
/dev/nvme0n1p5  819851264  821610495   1759232   859M Windows recovery environment
/dev/nvme0n1p6  821610496  916246527  94636032  45.1G Linux filesystem
/dev/nvme0n1p7  916246528  964739071  48492544  23.1G Linux filesystem
/dev/nvme0n1p8  964739072  983709695  18970624     9G Microsoft basic data
/dev/nvme0n1p9  983709696 1000214527  16504832   7.9G Linux swap
/dev/nvme0n1p10 762818560  819851263  57032704  27.2G Linux filesystem

Partition table entries are not in disk order.

Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 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
Disklabel type: gpt
Disk identifier: 8BEC7AEB-4576-42B0-8A8A-D40779A80126

Device          Start        End    Sectors  Size Type
/dev/sda1        2048    1026047    1024000  500M EFI System
/dev/sda2     1026048    1288191     262144  128M Microsoft reserved
/dev/sda3     1288192 1928626175 1927337984  919G Microsoft basic data
/dev/sda4  1928626176 1929547775     921600  450M Windows recovery environment
/dev/sda5  1929547776 1953523711   23975936 11.4G Windows recovery environment

As you can see both Windows 10 on SDD and HDD appear:


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