Ubuntu – How to get to Grub menu on 20.04

20.04bootgrub2

I've got this error when I try to boot my desktop up.

/tmp/mountroot-fail-hooks.d//scripts/init-premount/lvm2: No such file or directory

I'm running "on the metal" or whatever, no dual-boot anything.

I recently upgraded to 20.04 LTS from 18.04 LTS, but it ran fine until I started upgrading things and ran "autoclean", then reset.

I read that I should try for the Grub menu, and tried pressing ESC at the 5 dots loading screen, but holding it down just made it flicker between some kind of commandline / terminal, and the 5 dots.

I tried pressing ESC and holding C or any of the SHIFT keys during the terminal…

None of those got me to the Grub menu, whose appearance I looked up.

Oooh… Trying the "normal" command and hitting ESC while it was running got me to the GRUB Menu! Unfortunately, even doing the safe-mode parallel and running the package restorer didn't help.

How do I get to the Grub menu on 20.04 LTS Ubuntu?

Best Answer

If at 5 dots it usually is too late.

You use Escape key after UEFI screen but before grub normally shows.
Or if BIOS you press an hold shift key from BIOS screen until grub menu loads.

If you have UEFI fast boot on, you may not have time to press any key.
And if you changed grub timeout to 0 you may not be able to get grub menu.

Cold boot or full power down, may then then have system go back thru the full POST and give you just enough time to press keys.

If grub timeout at zero, check Boot-Repair's advanced options or a full reinstall of grub.

https://help.ubuntu.com/community/Boot-Repair

https://sourceforge.net/p/boot-repair/home/Home/

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Ubuntu – Upgrade to 20.04 from 18.04 GRUB menu hidden

Same problem though I installed Ubuntu 20.04 instead of upgrading.

A way for that: edit /etc/default/grub to change GRUB_TIMEOUT_STYLE=hidden to GRUB_TIMEOUT_STYLE=menu and remove # in front of #GRUB_TERMINAL=console. Finally, run sudo update-grub in terminal

Ubuntu – How to disable grub menu at boot time in Ubuntu 20.04

Tested with Dual boot of 2 Ubuntu 20.04 OS'es

Edit the below line in the file /etc/default/grub file

GRUB_TIMEOUT=10

like this

GRUB_TIMEOUT=0

and run the below command

sudo update-grub

this makes the timeout to 0 with condition that if there is Single OS it will stick to 0 otherwise it will be overwrite to 10.

In the /etc/grub.d/30_os-prober file, change the line

quick_boot="1"

quick_boot="0"

This will prevent in multi OS'es cases from changing the timeout value to 10seconds..

see the function "adjust_timeout" from the file /etc/grub.d/30_os-prober

prefix="/usr"
exec_prefix="/usr"
datarootdir="/usr/share"
quick_boot="1"

export TEXTDOMAIN=grub
export TEXTDOMAINDIR="${datarootdir}/locale"

. "$pkgdatadir/grub-mkconfig_lib"

found_other_os=

adjust_timeout () {
  if [ "$quick_boot" = 1 ] && [ "x${found_other_os}" != "x" ]; then
    cat << EOF
set timeout_style=menu
if [ "\${timeout}" = 0 ]; then
  set timeout=10
fi
EOF
  fi
}

When you want to see grub menu, pressing the Esc key at rite time will show you. (rite time varies based on conditions, generally after the BIOS menu hand overs to grub menu time)

In case if you wish to change Default OS, you can set from the same file /etc/default/grub.

for the first time, get to the grub menu by hitting Esc at the rite time. Then count the number starting from 0 from top to list your favorite OS Entry..

For example, I have two 20.04 OS'es.. one in /dev/sda2 and other in /dev/sda6 /dev/sda2 is the default one. If I want to make the one in /dev/sda6 as the default OS, I need to find its number like below..

So, its position is at number 2.

Edit the file /etc/default/grub and change the line

GRUB_DEFAULT=0

GRUB_DEFAULT=2

then run the below command

sudo update-grub

System will boot straight to Ubuntu 20.04 on /dev/sda6

Best Answer

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