Ubuntu – Grub wait time 10 seconds after editing to “0” in /etc/default/grub

15.04bootdual-bootgrub2

Using all of the solutions described on this site, setting the Grub menu wait time to zero does not work.

I did the following:

sudo cp /etc/default/grub /etc/default/grub.old    
sudo gedit /etc/default/grub

Uncommented this line, per instruction.

GRUB_HIDDEN_TIMEOUT="0"

Set this line, per instruction.

GRUB_TIMEOUT="0"

/etc/default/grub now looks like this:

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg. 
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

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

# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"

# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL="console"

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE="640x480"

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID="true"

# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"

# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"

Having edited the /etc/default/grub file –>

sudo update-grub

After restarting, Grub wait-time is still set to 10 seconds.

I was able to get the wait time to 1 second with just one simple change. Edited these two lines in /etc/default/grub 

#GRUB_HIDDEN_TIMEOUT="0"

GRUB_TIMEOUT="1"

Commented the first back to the default value, and set GRUB_TIMEOUT to "1".

After,

sudo update-grub

This solution works, but my question is:

Where is the trap that resets the TIMEOUT value to 10 seconds when GRUB-TIMEOUT is set to "0".

Maybe one of the "IF" tests in grub.cfg??

Best Answer

This is a bug. The problem is in the file /etc/grub.d/30_os-prober.

As presented here, a workaround is to add the files /etc/grub.d/25_pre-os-prober and /etc/grub.d/35_post-os-prober.

The two files must also be marked as executable to work.

After adding this two files, your modifications to the variable GRUB_TIMEOUT in /etc/default/grub should work as expected.

If you are not dual booting, another workaround is to uninstall os-prober.

25_pre-os-prober:

#! /bin/sh
# file: /etc/grub.d/25_pre-os-prober
set -e

# Save the $timeout and $timeout_style values set by /etc/grub.d/00_header
# before /etc/grub.d/30_os-prober messes them up.

cat << EOF
set timeout_bak=\${timeout}
set timeout_style_bak=\${timeout_style}
EOF

35_post-os-prober

#! /bin/sh
# file: /etc/grub.d/35_post-os-prober
set -e

# Reset $timeout and $timeout_style to their original values
# set by /etc/grub.d/00_header before /etc/grub.d/30_os-prober messed them up.

cat << EOF
set timeout=\${timeout_bak}
set timeout_style=\${timeout_style_bak}
EOF
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