How is grub updated after kernel installation

mra90 · 05-08-2019, 05:41 PM

Hello,

I install new kernel using debian packages, with command:

Code:

udo dpkg -i linux-*version*.deb

Now, I see right after this the next time I boot into my ubuntu 18.04 OS, new kernel was selected. However, I see no records in

Quote:

/etc/default/grub

There are entries for new kernel in:

Quote:

/boot/grub/grub/grub.cfg

However this file was autogenerated so modifying it makes no sense.

So, here is my question. How can I manually edit grub settings to boot kernel of choice?

BW-userx · 05-08-2019, 06:06 PM

post the contents of your

Code:

/etc/default/grub

file. that file is for editing, the grub.cfg is not.

when a new kernel is installed, (during update) it is usually followed by hook to update your cfg file automatically.

GNU GRUB Manual 2.02

mra90 · 05-10-2019, 04:30 PM

Thanks for the answer,

There are no words to express how GRUB annoys me

I try to setup default grub, I even found similar problem here

https://superuser.com/questions/2085...ernel-to-grub2

So what I do is I set GRUB_DEFAULT in /etc/default/grub to kernel name - FAIL, still boots the exact same kernel #0 from list. Then I didn't give up and try setting GRUB_DEFAULT to number/index regarding to menuentry in /boot/grub/grub.cfg - no luck again.

Here is content of my /etc/default/grub

Quote:

# 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=4
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=10
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
# 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"

Does anybody know why this crap doesn't boot the kernal I specify by GRUB_DEFAULT?

PS: of cource I do sudo grub-update after I change that /etc/default/grub file

colorpurple21859 · 05-10-2019, 04:52 PM

count from zero, so if it is the fourth menu entry then it would be 3

mra90 · 05-10-2019, 05:03 PM

@colorpurple21859 , good catch but it still not the problem since it boots #0 as I said ;/

colorpurple21859 · 05-10-2019, 06:05 PM

did you run

Code:

sudo update-grub

after making changes to /etc/default/grub?

colorpurple21859 · 05-10-2019, 06:10 PM

did you run

Code:

sudo update-grub

after making changes to /etc/default/grub? could also try grub_save default https://www.maketecheasier.com/set-g...ast-selection/

BW-userx · 05-10-2019, 06:39 PM

I cannot agree more, default is only on installed OS'e including Windows and other than Linux, it is zero based, every time you make changes to your /etc/default/grub file you have to update grub in order for the changes to take place.

mra90 · 05-10-2019, 07:51 PM

Guys you missed my "PS" section

Quote:

PS: of cource I do sudo grub-update after I change that /etc/default/grub file

Of course I updated grub

colorpurple21859 · 05-10-2019, 08:10 PM

If this is the only os on the system try disabling os-prober with this entry to your /etc/default/grub:
GRUB_DISABLE_OS_PROBER=true

BW-userx · 05-10-2019, 08:32 PM

and put the other back to zero (0)

mra90 · 05-11-2019, 05:20 AM

@colorpurple21859, I have added you suggestion "GRUB_DISABLE_OS_PROBER=true" but still grub boots the very first kernel from /boot/grub/grub.cfg

Below content of /etc/default/grub I have now:

Quote:

# 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="gnulinux-4.9.45-upboard+-advanced-d5007568-bf96-4bc4-9723-a0d06b750cb4"
GRUB_DISABLE_OS_PROBER=true
GRUB_SAVEDEFAULT=true
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

mra90 · 05-11-2019, 05:39 AM

UPDATE:

I managed to boot into kernel of my choice by changing order of "menuentry" in /boot/grub/grub.cfg. However this is not a solution, rather a quick and dirty hack ;/

So everytime I will update-grub I will lose my settings too...

colorpurple21859 · 05-11-2019, 06:39 AM

change this

Quote:

GRUB_DEFAULT="gnulinux-4.9.45-upboard+-advanced-d5007568-bf96-4bc4-9723-a0d06b750cb4"

to

Code:

GRUB_DEFAULT=saved

in /etc/default/grub
after selecting the kernel you want to use on the first boot, it should save it for the next boot untill it is changed again.

mra90 · 05-11-2019, 06:47 AM

colorpurple21859, I don't see how could it help.

Code:

GRUB_DEFAULT=saved

where do we specify what kernel to boot as default?