Manually UEFI Boot Linux and Windows 10 USB from Grub

I'm using Dell Inspiron 7420 as a demo, and its BIOS is Phoenix A19.

Old BIOS is likely not to get configurations correct, and the support for UEFI is miserable in convenience.

Mostly boot configurations are in BOOT tab, and after you select that you would like to boot in UEFI mode, you will see that your USB is listed as a boot choice, like following:

Note: The boot flag might be set improperly if you cannot see any USB related stuffs here

Normally it is a convention for UEFI compatible devices to install a bootloader in /efi/boot/boot<arch-name>.efi for itself.

For example, x86_64 should be: /efi/boot/bootx64.efi

And therefore, you can Add a boot option, and fill-in as following:

Note 1: UEFI path's slash is compatible with Microsoft path which uses \, Linux's / path is not supported. Note 2: UEFI treats path case-insensitive

Afterwards, you should make USB boot option first.

Save and reboot.

After reboot, you'll see the installation grub menu.

If there's something wrong here, and you got into the grub rescue terminal, like the following:

You'll need to boot from USB manually.

# Use `ls` to list bootable devices
grub> ls
(hd0) (hd0,msdos1) ...

# The `0` in `hd0` is the device id, and the `1` in `msdos1`
# is the partition id.
# If you're booting from USB, it is most likely to
# name the USB itself as hd0

# You need to set root to one partition before
# viewing any files
grub> set root=hd0,msdos1

# Then you can view its files.
# (Make sure you're booting from the correct partition)
grub> ls /
boot  [BOOT]  casper  dists  EFI  install  isolinux  md5sum.txt  pics  pool  preseed  README.diskdefines

# Afterwards, you can boot manually using the following commands
grub> linux /casper/vmlinuz.efi boot=casper quiet splash
grub> initrd /casper/initrd.lz
grub> boot

Before you install the distribution on your disk, you should check whether you're actually booting from UEFI mode.

To check whether you're booting in UEFI mode, use:

[ -d /sys/firmware/efi ] && echo "UEFI" || echo "Legacy"

1. Copy EFI and boot directory from ISO into your USB disk

   Note: You can use mount to mount the ISO to a directory

     sudo mount -o loop ~/Ubuntu-16.04-desktop-amd64.iso /mnt
     cp -r /mnt/EFI/ /mnt/boot/ <USB mount point>
   

2. Copy the ISO file into <USB mount point>/EFI/BOOT/

3. Edit the grub.cfg at <USB mount point>/boot/grub/grub.cfg

   For example, to boot Ubuntu 16.04 from ISO Image

   1. You should correctly setup isofile path
   2. Use loopback to create loopback device mapping to the content of the fs in ISO
   3. Add iso-scan/filename=$isofile to linux command parameters

     menuentry "Boot Ubuntu 16.04 from ISO" {
       set isofile="/efi/boot/ubuntu-16.04-desktop-amd64.iso"
       loopback loop $isofile
       linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile noprompt noeject quiet splash
       initrd (loop)/casper/initrd.lz
     }
   

4. Copy Other ISOs into <USB mount point>/EFI/BOOT/

5. Edit the grub.cfg again to add other menus

   Take Fedora 25 as an example:

   You should always reference to the original grub.cfg in the ISO to get a brief example of how it should be booted.

     menuentry "Boot Fedora 25 from ISO" {
       set isofile="/efi/boot/Fedora-Workstation-Live-x86_64-25-1.3.iso"
       loopback loop $isofile
       linuxefi (loop)/images/pxeboot/vmlinuz iso-scan/filename=$isofile root=live:CDLABEL=Fedora-WS-Live-25-1-3 rd.live.image quiet
       initrdefi (loop)/images/pxeboot/initrd.img
     }
   

6. The final directory structure should look like:

     >> tree <USB mount point>
     .
     ├── boot
     │   └── grub
     │       ├── efi.img
     │       ├── font.pf2
     │       ├── grub.cfg
     │       ├── loopback.cfg
     │       └── x86_64-efi
     │           └── ...
     └── EFI
         └── BOOT
   	  ├── BOOTx64.EFI
   	  ├── Fedora-Workstation-Live-x86_64-25-1.3.iso
   	  ├── grubx64.efi
   	  └── ubuntu-16.04-desktop-amd64.iso
   

7. Reboot and choose whatever you want

It only differs in first step from the easy choice. In easy choice, we're using the ubuntu's default grub image.

Here we can make a customized one.

1. Install the grub's EFI version

     sudo apt install grub-efi-amd64-bin
   

2. Use grub-mkimage to create a boot image (man grub-mkimage for help)

   You may choose what mod to pack. For example:

     grub-mkimage -o bootx64.efi -p /efi/boot -O x86_64-efi \
       all_video boot btrfs cat chain \
       configfile echo efi_gop efi_uga \
       efifwsetup exfat ext2 fat \
       gfxterm gfxterm_background gfxterm_menu \
       hfsplus iso9660 linux loadenv \
       loopback ls lsefi normal ntfs \
       part_gpt part_msdos search search_fs_file \
       search_fs_uuid search_label test udf usb
   

   Put it to <USB mount point>/EFI/BOOT/

3. The grub.cfg in following steps should be put <USB mount point>/EFI/BOOT/ directory

4. The final directory structure would be:

     >> tree <USB mount point>
     .
     └── EFI
         └── BOOT
   	  ├── Fedora-Workstation-Live-x86_64-25-1.3.iso
   	  ├── bootx64.efi
   	  ├── grub.cfg
   	  └── ubuntu-16.04-desktop-amd64.iso