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I have Ubuntu (18.04) and Windows 10 (May 2019 Update) installed on separate hard drives. This works, in a manner. Without entering the grub menu my system boots into Ubuntu. I can use Grub2 to boot into Windows 10. However, to do so, I have to:

  1. Enter the grub menu
  2. Try booting into Windows 10
  3. Receive an error: "invalid EFI file path"
  4. Press "escape" to enter a grub terminal
  5. Type "exit" to leave the terminal (and grub)

After this, the system boots into Windows 10 successfully. My custom grub entry (/etc/grub.d/40_custom) is:

menuentry "Windows 10" --class windows --class os {
    insmod part_msdos
    insmod ntsf
    search --no-floppy --fs-uuid --set=root MY_UUID
    chainloader +1
}

The UUID I am using points to the larger partition of the following:

Device     Boot       Size    Type
/dev/sdb1  *    ...   238G    HPFS/NTFS/exFAT
/dev/sdb2       ...   474M    Hidden NTFS WinRE

No additional information is given about these partitions when I run lsblk or blkid.

My question is, why does this still work, and can I modify my custom grub entry so that it works when I select it, rather than after doing what I do above?

cpaynerogers
  • 21
  • Most probably you mixed up boot-modes (Windows is installed in legacy-mode, Ubuntu in UEFI-mode). What happens if you type exit in the Grub-command-line is that the boot failed and the firmware switches to the next entry in the boot-order list which is Windows in your case. – mook765 Sep 15 '19 at 04:29
  • Is there a way for me to keep these mixed boot modes and avoid the error, or should one be changed to match the other? – cpaynerogers Sep 16 '19 at 17:44
  • To achieve a proper dual-boot, both systems should be installed in the same boot-mode. Examine your system first. Windows boot-mode is bound to partition-taple-type (msdos=legacy, GPT=UEFI). For Ubuntu take a look here. If boot-modes doesn't match you should convert one of the OS. But there is no harm in leaving it as it is, you can directly boot from UEFI-boot-menu without error, but maybe that's inconvenient. You can not modify your custom grub entry to get it done if boot-modes doesn't match. – mook765 Sep 16 '19 at 18:06
  • This all makes sense, I'll see if I can get everything squared away, thanks! – cpaynerogers Sep 18 '19 at 18:08

0 Answers0