IRC:grub-saved [2020-01-21*]

Copy the following line to a terminal:

df -Th /boot/grub

This should show some similar output:

Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/sda5      ext4   61G   33G   25G  58% /

- where the column Type is important and should show preferable 'ext4', 'ext3' or 'ext2'.

If the shown type is 'btrfs', you can stop here, as grub does not support the grub-saved feature in this case.

Copy the following lines to a terminal:

mkdir ~/backups
cp --parents --backup=numbered /etc/default/grub  ~/backups

This will create a folder backups at your users home-directory and place a copy of the original file, including it's parent folders structure there.

If the cp command is run repeatedly, older backups will be kept, but renamed to grub~1~, grub~2~ etc - the last recent version will keep the original name.

Copy the following line to a terminal and enter your password, when being asked (2 times on the first run):

xed admin:///etc/default/grub

Note: If you cant use xed for some reason or are limited to a text-console, you can use nano - see IRC:nano.htm - instead, to apply the required changes:

sudo nano /etc/default/grub

Replace the line showing GRUB_DEFAULT=0 with GRUB_DEFAULT=saved

Add a new line below GRUB_SAVEDEFAULT=true

Replace the line showing GRUB_TIMEOUT=0 with GRUB_TIMEOUT=3

If you want to display the grub-menu on boot without an user action, you can optionally replace GRUB_TIMEOUT_STYLE=hidden with GRUB_TIMEOUT_STYLE=menu

The final file will look similar to this (edit's are highlighted, leading and subsequent text is omitted)

# ... skipped text before
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true
GRUB_TIMEOUT_STYLE=menu		# optional to show the grub-menu without user action
GRUB_TIMEOUT=3
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

# Uncomment to enable BadRAM filtering, modify to suit your needs
# skipped text after ...

Save your changes and close the editor.

To re-create the actual grub-menu run:

sudo update-grub

, which should list available kernels and installed OS - similar to this:

demo@mint-19-3-cinnamon-64bit:~$ sudo update-grub
[sudo] password for demo:         
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50_linuxmint.cfg'
Sourcing file `/etc/default/grub.d/60_mint-theme.cfg'
Generating grub configuration file ...
Found theme: /boot/grub/themes/linuxmint/theme.txt
Found linux image: /boot/vmlinuz-5.3.0-26-generic
Found initrd image: /boot/initrd.img-5.3.0-26-generic
Found linux image: /boot/vmlinuz-5.0.0-37-generic
Found initrd image: /boot/initrd.img-5.0.0-37-generic
Found linux image: /boot/vmlinuz-5.0.0-32-generic
Found initrd image: /boot/initrd.img-5.0.0-32-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
demo@mint-19-3-cinnamon-64bit:~$

If update-grub does show any errors: recheck your edits. It might help to compare your edits against the initial created backup-file using:

diff /etc/default/grub  ~/backups/etc/default/grub

demo@mint-19-3-cinnamon-64bit:~$ diff /etc/default/grub  ~/backups/etc/default/grub
6,9c6,8
< GRUB_DEFAULT=saved
< GRUB_SAVEDEFAULT=true
< GRUB_TIMEOUT_STYLE=menu
< GRUB_TIMEOUT=3
---
> GRUB_DEFAULT=0
> GRUB_TIMEOUT_STYLE=hidden
> GRUB_TIMEOUT=0
demo@mint-19-3-cinnamon-64bit:~$