Manjaro os-prober can't detect Windows without Windows Boot Manager

I have a dual boot setup on my SSD.

The partition structure is as follows:


  • Manjaro EFI/Boot partition
  • Manjaro root partition
  • Windows C:/ partition
  • 100mb Unallocated partition
  • Windows Recovery Partition

Hard Drive

  • Manjaro /home partition
  • Ubuntu EFI/Boot partiton
  • Ubuntu main partition
  • Windows F:/ partition

The subesquent fdisk -l result:

Disk /dev/sda: 698.65 GiB, 750156374016 bytes, 1465149168 sectors
Disk model: WDC WD7500AALX-0
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: dos
Disk identifier: 0x6899a761

Device     Boot     Start        End   Sectors   Size Id Type
/dev/sda1  *    732573696 1465147391 732573696 349.3G  7 HPFS/NTFS/exFAT
/dev/sda2            2048  661030483 661028436 315.2G 83 Linux
/dev/sda3       661030912  662081535   1050624   513M  b W95 FAT32
/dev/sda4       662083582  732573695  70490114  33.6G  5 Extended
/dev/sda5       662083584  732573695  70490112  33.6G 83 Linux

Partition table entries are not in disk order.

Disk /dev/sdb: 119.25 GiB, 128035676160 bytes, 250069680 sectors
Disk model: SanDisk SD8SBAT1
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: dos
Disk identifier: 0xd6a6180c

Device     Boot     Start       End   Sectors  Size Id Type
/dev/sdb1  *    129024000 248762367 119738368 57.1G  7 HPFS/NTFS/exFAT
/dev/sdb2       248967168 250052607   1085440  530M 27 Hidden NTFS WinRE
/dev/sdb3            2048    206847    204800  100M  c W95 FAT32 (LBA)
/dev/sdb4          206848 129023999 128817152 61.4G 83 Linux

Partition table entries are not in disk order.

After a lot of research looking at several threads I have come across the following conclusions:

  • The Ubuntu GRUB does not load the kernel so cannot boot Manjaro.
  • The Manjaro GRUB can boot Ubuntu.
  • The os-prober for Ubuntu detects and adds windows.
  • The os-prober for Manjaro does not detect and add windows.
  • Copying the Ubuntu menuentry for Windows does not solve the problem even after chainng the hard drive number
  • My laptop has Manjaro GRUB and detects Windows because I still have the Windows bootloader partition on that device.
  • I was planning on using the 100mb partiton for windows boot manager however then I exceed the 4 primary partitons limit of GPT.

As a result I am going to delete the windows recovery partition so I can add a Windows boot manager. However this seems unnecesary. If there is anything that can be done to help before I do so please comment.

The Windows 10 menuentry that Ubuntu os-prober creates:

menuentry 'Windows 10 (on /dev/sdb1)' --class windows --class os $menuentry_id_option 'osprober-chain-01D176FA55F92D30' {
	insmod part_msdos
	insmod ntfs
	set root='hd1,msdos1'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,msdos1 --hint-efi=hd1,msdos1 --hint-baremetal=ahci1,msdos1  01D176FA55F92D30
	  search --no-floppy --fs-uuid --set=root 01D176FA55F92D30
	parttool ${root} hidden-
	#drivemap -s (hd0) ${root}
	chainloader +1

You have no GPT there. Both your HDDs are dos aka MBR that has the limitation you mentioned. GPT has no such limitation because those partitions can be 128 and are not "primary" per se ...

Because of that confusion you had, i'm not even sure if your

is ok, or even if your system is UEFI system ...
Share from terminal:
inxi -Fxxxza --no-host
Hopefully someone, with a clear mind and ready to dedicate some time for this, will join in. :slight_smile: Or maybe you will realize what you "overcomplicated".

1 Like

I don't see why you need this much information but there you go. Yes you are correct they both use MBR. I apologize for my incorrect labelling:

System:    Kernel: 5.6.16-1-MANJARO x86_64 bits: 64 compiler: gcc v: 10.1.0 
           parameters: BOOT_IMAGE=/boot/vmlinuz-5.6-x86_64 root=UUID=3ddbb010-7ad9-4050-a75a-561427e9b785 rw 
           loglevel=3 quiet 
           Desktop: KDE Plasma 5.18.5 tk: Qt 5.15.0 info: latte-dock wm: kwin_x11 dm: SDDM Distro: Manjaro Linux 
Machine:   Type: Desktop Mobo: ASRock model: B450M Pro4 serial: <filter> UEFI: American Megatrends v: P3.90 
           date: 12/09/2019 
CPU:       Topology: 6-Core model: AMD Ryzen 5 3600 bits: 64 type: MT MCP arch: Zen family: 17 (23) 
           model-id: 71 (113) stepping: N/A microcode: 8701013 L2 cache: 3072 KiB 
           flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm bogomips: 91067 
           Speed: 3793 MHz min/max: 2200/3800 MHz boost: enabled Core speeds (MHz): 1: 3793 2: 3793 3: 3793 
           4: 3793 5: 3793 6: 3792 7: 3792 8: 3792 9: 3790 10: 3793 11: 3793 12: 3793 
           Vulnerabilities: Type: itlb_multihit status: Not affected 
           Type: l1tf status: Not affected 
           Type: mds status: Not affected 
           Type: meltdown status: Not affected 
           Type: spec_store_bypass mitigation: Speculative Store Bypass disabled via prctl and seccomp 
           Type: spectre_v1 mitigation: usercopy/swapgs barriers and __user pointer sanitization 
           Type: spectre_v2 mitigation: Full AMD retpoline, IBPB: conditional, STIBP: conditional, RSB filling 
           Type: tsx_async_abort status: Not affected 
Graphics:  Device-1: NVIDIA GK208B [GeForce GT 710] vendor: driver: nouveau v: kernel bus ID: 06:00.0 
           chip ID: 10de:128b 
           Display: x11 server: X.Org 1.20.8 driver: nouveau unloaded: modesetting alternate: fbdev,nv,vesa 
           compositor: kwin_x11 resolution: 1920x1080~60Hz 
           OpenGL: renderer: NV106 v: 4.3 Mesa 20.0.7 direct render: Yes 
Audio:     Device-1: NVIDIA GK208 HDMI/DP Audio vendor: driver: snd_hda_intel v: kernel 
           bus ID: 06:00.1 chip ID: 10de:0e0f 
           Device-2: Advanced Micro Devices [AMD] Starship/Matisse HD Audio vendor: ASRock driver: snd_hda_intel 
           v: kernel bus ID: 08:00.4 chip ID: 1022:1487 
           Device-3: Microdia USB 2.0 Camera type: USB driver: snd-usb-audio,uvcvideo bus ID: 3-2:2 
           chip ID: 0c45:62f1 
           Sound Server: ALSA v: k5.6.16-1-MANJARO 
Network:   Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet vendor: ASRock driver: r8169 
           v: kernel port: f000 bus ID: 04:00.0 chip ID: 10ec:8168 
           IF: enp4s0 state: up speed: 1000 Mbps duplex: full mac: <filter> 
Drives:    Local Storage: total: 817.88 GiB used: 59.65 GiB (7.3%) 
           ID-1: /dev/sda vendor: Western Digital model: WD7500AALX-009BA0 size: 698.64 GiB block size: 
           physical: 512 B logical: 512 B speed: 3.0 Gb/s serial: <filter> rev: 1H15 scheme: MBR 
           ID-2: /dev/sdb vendor: SanDisk model: SD8SBAT128G1122 size: 119.24 GiB block size: physical: 512 B 
           logical: 512 B speed: 6.0 Gb/s serial: <filter> rev: 0000 scheme: MBR 
Partition: ID-1: / raw size: 61.42 GiB size: 60.21 GiB (98.02%) used: 11.43 GiB (19.0%) fs: ext4 dev: /dev/sdb4 
           ID-2: /home raw size: 315.20 GiB size: 309.26 GiB (98.11%) used: 48.22 GiB (15.6%) fs: ext4 
           dev: /dev/sda2 
Sensors:   System Temperatures: cpu: 39.1 C mobo: N/A gpu: nouveau temp: 45 C 
           Fan Speeds (RPM): N/A 
Info:      Processes: 280 Uptime: 58m Memory: 15.57 GiB used: 2.14 GiB (13.7%) Init: systemd v: 245 Compilers: 
           gcc: 10.1.0 Shell: bash v: 5.0.17 running in: konsole inxi: 3.0.37

I apologize, there is not EFI/Boot partiton for Manjaro (I've done too much partitioning recently). However, nevertheless the point stands

Installed in UEFI mode, but for that you need GPT partition table with proper boot loaders, in the correct place/partition, and with correct flag. Now is a bit of a mess to be honest (no derogatory meaning). I can understand that circumstances can lead to make things a bit sloppy.

And i recon you will still do that, and a couple of new installs, all your OSs, to make things work properly :slight_smile:

Yes, os-prober fails to detect the convoluted way the situation is with your installs.

Enciclopedia Britanica is much information, the inxi is the standard information we require here in the forum.


1 Like

So I think your problem lies with the mix of the two.

You need to decide if you are going dos or gpt - you cannot do both.

4 primary partitions is a limitation on MBR and has nothing to do with GPT which limitation - by the way - is 128 .

You can't create an EFI partition on MBR partition schema (the utility used should throw a gigantic - no can do) and you cannot boot EFI on MBR partition schema.

While it is possible to combine GPT partition schema with a BIOS boot - this requires a special unformatted partition flagged as bios-boot (0xEF02 if memory serves).

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