GRUB COMMAND

press 'c' while launching to interrupt grub launching and entre in grub command

CHANGE GRUB DISPLAY RESOLUTION

vbeinfo # list available resolutions

modify in /etc/default/grub (ex: 800x600)

GRUB_GFXMODE=$resolution

CLEAR SECTOR 32

dd if=/dev/zero of=/dev/sda bs=512 count=1 seek=32
grub-install $device

USB3 MSI GAMING

add in /etc/default/grub

GRUB_CMDLINE_LINUX="iommu=soft"

LXD

/etc/default/grub

GRUB_CMDLINE_LINUX="... systemd.unified_cgroup_hierarchy=0

GRUB_TIMEOUT

Modify set timeout for choosed value in /boot/grub/grub.cfg

if [ "$recordfail_broken" = 1 ]; then
    cat << EOF
    if [ \$grub_platform = efi ]; then
        set timeout=${GRUB_RECORDFAIL_TIMEOUT:-30}
        if [ x\$feature_timeout_style = xy ] ; then
            set timeout_style=menu
        fi
    fi
    EOF
fi

MANJARO

OS real name for btrfs

file="/etc/grub.d/30_os-prober"
file_keep="$file.keep$(date +%s)"
if ! grep -q 'LONGNAME="${LONGNAME} ${BTRFSsubvol/#subvol=/}"' "$file"; then
    sudo cp -a "$file" "$file.keep$(date +%s)" && sudo chmod -x "$file_keep"
    sudo sed -i "/LONGNAME=\"\${LABEL}\"/ a\  else\n    LONGNAME=\"\${LONGNAME} \${BTRFSsubvol/#subvol=/}\"" "$file"
    sudo update-grub
fi

UBUNTU 18.04

Remove error in startup log : systemd-backlight@backlight:acpi_video0.service, add in /etc/default/grub

acpi_osi='!Windows 2012' 
acpi_backlight=vendor in GRUB_CMDLINE_LINUX_DEFAULT  in /etc/default/grub

BOOT ENTRY

https://linux.die.net/man/8/efibootmgr

efibootmgr

efibootmgr # list all boot entries
-v # list all boot entries with details
-B -b XXXX # delete boot entry number XXXX

example for 970g

efibootmgr -c -g -d /dev/sda1 -p 1 -w -L 'Manjaro' -l '\EFI\Manjaro\grubx64.efi'
efibootmgr -c -g -d /dev/sda1 -p 1 -w -L 'ubuntu' -l '\EFI\ubuntu\shimx64.efi'
efibootmgr -c -g -d /dev/sda1 -p 1 -w -L 'Windows Boot Manager' -l '\EFI\Microsoft/Boot\bootmgfw.efi'

>>

Timeout: 1 seconds
BootOrder: 0000,0001,0002
Boot0000* Manjaro HD(1,GPT,8e91a305-046d-4e90-8548-efca286325a7,0x800,0x32000)/File(\EFI\Manjaro\grubx64.efi)
Boot0001* ubuntu  HD(1,GPT,8e91a305-046d-4e90-8548-efca286325a7,0x800,0x32000)/File(\EFI\ubuntu\shimx64.efi)
Boot0002* Windows Boot Manager  HD(1,GPT,8e91a305-046d-4e90-8548-efca286325a7,0x800,0x32000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)