Migrating from 20.04 -> 22.04 -> 24.04 on headless Ubuntu server + hardware upgrade

[Bo Berglund]

So I have this old server system which still runs Ubuntu 20.04.6 LTS server on a
Lenovo Ideacenter minitower and I want to do these things:

1) Make it use the latest kernel for that Ubuntu version.
For some reason it is stuck at Kernel 5.4.0-89.100-generic even though several
later ones have been provided by the apt system. But it has not switched kkernel
even though I have restarted it several times.

$ uname -r
5.4.0-89-generic

$ dpkg --list 'linux-image*' | grep ^ii
ii linux-image-5.15.0-126-generic  5.15.0-126.136~20.04.1 amd64 Signed kernel
image generic
ii linux-image-5.4.0-200-generic   5.4.0-200.220          amd64 Signed kernel
image generic
ii linux-image-5.4.0-89-generic    5.4.0-89.100           amd64 Signed kernel
image generic
ii linux-image-generic             5.4.0.200.196          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

I believe I will not get the offer to do a release upgrade unless I can make it
use a later kernel.
This server is "mission-critical" so I cannot make a mistake in the upgrade
process, I need a full disk backup before I even embark on this, but the problem
is how to do that.
I probably have to boot into a usb system with GParted to do the disk partition
copies....

2) Upgrade it to 22.04 and then to 24.04 using the do-release-upgrade command
Once I have the backup done as above and somehow can make it use the latest
kernel, then I want to do the transfer to 24.22.4 via 22.04.4

If that fails for some reason I need to bring back the original disk content to
the drive (probably only the partitions used by 20.04.6, there are also a
windows set of partitions, but that and the data partitions will not have
changed.

3) Finally I want to move the entire system to a new ASUS NUC 13 i7 device to
get rid of the Windows dependency of the Lenovo I am now using.

Question:
Can I just copy the final partitions of the converted Ubuntu to the drive in the
NUC and start it to make it run my old server system?

Or else - how can I make the move to new hardware?

I cannot install a fresh system on the NUC because I have no idea how to then
install all of the already configured services on the new hardware platform
fresh from start...

I simply do not now remember what I have done over the years to
install/configure these since 2017 when it was originally built...

Or can a switch of hardware not be done?


-- 
Bo Berglund
Developer in Sweden