Can't reduce the countdown time from the default 30 seconds in grub 2.04. I am running a fresh Xubuntu 20.04 LTS, with the addition that I've installed newer kernel images, to get access to my CPU temperature.

What I've tried:

• changed GRUB_TIMEOUT in /etc/default/grub


• set quickboot to 0 and changed timeout as suggested here


• changed GRUB_TIMEOUT_STYLE to menu and countdown as proposed in here and in another link I do not find at the moment.


• Commented out the last line (adjust_timeout) in /etc/grub.d/30_os-prober

After all of these steps I've run sudo update-grub, which run without any error.

My /etc/default/grub file without comments:

GRUB_DEFAULT=0

GRUB_TIMEOUT_STYLE=countdown

GRUB_TIMEOUT=3

GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`

GRUB_CMDLINE_LINUX_DEFAULT=""

GRUB_CMDLINE_LINUX=""

Edit

Right after I've written the question down, I've made another try. I grep-ed all files in /etc/grub.d which had the string 30 in it. Only 00_header has it at two places. The big part of this file is a make_timeout function. This part of the script is reached only if "$recordfail_broken" = 1 or "${recordfail}" = 1. So it indicates that something went wrong, and I probably should debug it, though I have not experienced any drawbacks yet. For the time being I've changed those values from 30 to 3.