Grub2 setup

To configure GRUB so that it always appears

This example uses the nano editor

After booting into Ubuntu, open a terminal Ctrl Alt t and enter

sudo nano /etc/default/grub

Enter your user password

Locate the lines similar to below

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
GRUB_DISABLE_OS_PROBER=true

Change two lines as follows

GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10

GRUB_TIMEOUT is the delay in seconds before Ubuntu boots

Ctrl o to save and Ctrl x to exit nano

Remain in the terminal and update grub

sudo update-grub

Output similar to below

sudo update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/kdump-tools.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-7.0.0-38-generic
Found initrd image: /boot/initrd.img-7.0.0-38-generic
Found linux image: /boot/vmlinuz-7.0.0-34-generic
Found initrd image: /boot/initrd.img-7.0.0-34-generic
Found linux image: /boot/vmlinuz-7.0.0-31-generic
Found initrd image: /boot/initrd.img-7.0.0-31-generic
Found memtest86+ 64bit EFI image: /boot/mt86+x64
Found memtest86+ 32bit EFI image: /boot/mt86+ia32
Found memtest86+ 64bit image: /boot/mt86+x64
Found memtest86+ 32bit image: /boot/mt86+ia32
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...
done

Close terminal, power off and power on to check that the grub edits have been successful

Comments

Allowing Grub to appear offers, at least, two user benefits:-

Easy access to Advanced Options > Recovery Mode
Convenient path to UEFI Settings