How do I know which grub version is used and how to configure it?

[Bo Berglund]

I am struggling with my Ubuntu server system, which is now dist-upgraded to
24.04.1.

But there is also another Ubuntu desktop 20.04 on the disk and it was shown
earlier on the boot menu, but now gone.

And the current kernel displayed by uname -r is even after a reboot:

5.15.0-126-generic

But I have the following available:

$ dpkg --list 'linux-image*' | grep ^ii
ii  linux-image-5.15.0-126-generic  5.15.0-126.136       amd64  Signed kernel
image generic
ii  linux-image-6.8.0-50-generic  6.8.0-50.51            amd64  Signed kernel
image generic
ii  linux-image-6.8.0-51-generic  6.8.0-51.52            amd64  Signed kernel
image generic
ii  linux-image-generic           6.8.0-51.52            amd64  Generic Linux
kernel image
ii  linux-image-generic-hwe-20.04 5.15.0.126.136~20.04.1 amd64  Generic Linux
kernel image

But on the boot menu I see no sign of the 6.8.0 kernels...

So my question is if I am updating the wrong grub, since I have seen that there
is also a grub2 online?

What is the difference grub vs. grub2 and how can I determine which is in use?
And how can I correctly update the menu to show the actual server version
instead of showing 20.04.6, which it was prior to my dist-upgrade?

Can I switch between the kernels, somehow?

I have found the document https://help.ubuntu.com/community/Grub2 but I am still
unsure on how to use it, for example if/how I can add a menu entry myself into
the config file:

/etc/grub.d$ nano 40_custom

I would very much want to add the "Ubuntu Server 24.04.1" to it since it does
not appear as such on the actual visible grub menu on start, instead it shows:

Ubuntu 20.04.6 LTS (20.04) (on /dev/nvme0n1p6)

It should read:

Ubuntu 24.04.1 LTS (24.04) (on /dev/nvme0n1p6)


And the main config file /etc/default/grub file just contains this:

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"

Nothing about the menu entries....
????


-- 
Bo Berglund
Developer in Sweden