Notes related to Extensible Firmware Interface (EFI).

== Reboot into BIOS ==

{{{#!highlight sh numbers=off
sudo systemctl reboot --firmware-setup
}}}

[[https://superuser.com/a/1083166/20815|Ref]]

== Repair for Linux ==

To reinstall UEFI entries, check what's installed with `efibootmgr --verbose` which will list all boot entries, and the default. If the entry for the OS is missing (usually "debian" or "ubuntu"), the entry may need to be re-added. Rather than manipulating EFI variables, it's easiest to reinstall grub which ensures all files/etc are in the right place.

If using a chroot to reinstall entries, first setup various bind mounts from outside the chroot into the chroot:

{{{#!highlight sh
CHROOT_ROOT=/mnt
# mount --bind /dev/ $CHROOT_ROOT/dev
# mount --bind /dev/pts $CHROOT_ROOT/dev/pts
# OR
mount --rbind /dev/ $CHROOT_ROOT/dev
mount --bind /sys $CHROOT_ROOT/sys
mount --bind /proc $CHROOT_ROOT/proc
mount --rbind /run $CHROOT_ROOT/run

modprobe efivarfs
mount -o bind /sys/firmware/efi $CHROOT_ROOT/sys/firmware/efi
}}}
Also ensure the EFI partition is mounted at the correct location (e.g. usually `/boot/efi`).

After entering the chroot, reinstall grub with:

{{{#!bash
grub-install --target=x86_64-efi --efi-directory=/boot/efi 
}}}

Afterwards, double-check the boot entry shows up with `efibootmgr`.

== efibootmgr ==

{{{#!bash
# On a Debian system
$ sudo efibootmgr --unicode
BootCurrent: 0006
BootOrder: 0006,0004
Boot0000* Hard drive C: VenHw(d6c0639f-c705-4eb9-aa4f-5802d8823de6)�
Boot0001* IBA XE Slot 0100 v2434        BBS(128,IBA XE Slot 0100 v2434,0x0)�
Boot0004* Integrated NIC 1 Port 1 Partition 1   VenHw(3a191845-5f86-4e78-8fce-c4cff59f9daa)
Boot0006* debian        HD(1,GPT,d29fd1bb-05db-40a8-bedd-7e781d884cdc,0x800,0xf3800)/File(\EFI\debian\shimx64.efi)

# On an Ubuntu system
$ sudo efibootmgr --unicode
BootCurrent: 0001
Timeout: 0 seconds
BootOrder: 0001,2001,2002,2003
Boot0001* Kubuntu       HD(1,GPT,9c2855d5-633e-4091-aa3c-40e172d0ecfc,0x1000,0x96000)/File(\EFI\kubuntu\shimx64.efi)
Boot2001* EFI USB Device        䍒
Boot2002* EFI DVD/CDROM 䍒
Boot2003* EFI Network   䍒

OR

Boot0006* ubuntu        HD(1,GPT,2535f000-ca5e-42fa-b4fd-1a40e99a5ed5,0x1000,0x96000)/File(\EFI\ubuntu\shimx64.efi)

# Delete unused boot entries
$ efibootmgr --delete-bootnum --bootnum 0007

# Create new entry (preferably, use grub-install)
$ efibootmgr --create --disk /dev/sda --part 1 --loader "\EFI\debian\shimx64.efi" --label "debian"
}}}

== Links ==

 * [[https://maple52046.github.io/2017/11/03/Install-Ubuntu-in-UEFI-mode-with-debootstrap/|Install Ubuntu in UEFI mode with debootstrap]]
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