Upgrade Ubuntu from 22.04.4 LTS to 24.04.0 LTS

 Ubuntu 24.04.0 LTS Noble Numbat was released on 2024-04-26.

By default, it is not available for previous Ubuntu LTS version as stable, before version 24.04.1 (which is scheduled for the 15th of August), but it can still be installed using the development flag, when using do-release-upgrade tool.

The main steps are explained in the official upgrade documentation, and if needed you can still check troubleshooting.

My recommandations are:

 - ofc, perform the following instructions, before anything else

sudo apt update && sudo apt upgrade 

 - IMPORTANT: during the upgrade process, system can break itself, updating some net packages, preventing apt itself to keep on downloading packages; to prevent that, download libnettle8 package from https://packages.ubuntu.com/noble/amd64/libnettle8t64/download on your computer

- do NOT perform the upgrade in graphical mode, because the upgrade process will break it, and it will be hard to recover manually, if you are not used to it; thus start by switching to multi-user target (formerly known as runlevel 3)

sudo systemctl isolate multi-user.target

- alternatively, if you use grub as boot loader, you can still edit menu item adding a '3' (without quotes) at end of the kernel line, to force a runlevel 3 start

- start the upgrade (reminder: if you are under 22.04.4 LTS, and perform the upgrade before release of 24.04.1 LTS, you need the development flag, which is enabled with the -d option)

sudo do-release-upgrade -d

- if ever you have issue (e.g. interrupt) during the upgrade process, you can still request system to continue, with the following instructions

sudo dpkg --configure -a

sudo apt-get upgrade --fix-broken

- IMPORTANT: if you use a Desktop version, ensure the xserver-xorg-input-all package is installed (otherwise you may have no response from keyboard and mouse, once X is started)

sudo apt install xserver-xorg-input-all

- before restarting, ensure your free or proprietary graphical driver are installed

- after restart, if you have any issue, you can still select a rescue mode item in bootloader menu, then you can request networking enabling, and then package installation fix, or request an admin terminal, and use any required instructions you want

 - after reboot, ensure everything has been properly upgraded, with - again - the following instructions

sudo apt update && sudo apt upgrade 

- if you have dependencies issues (I got some with libboost), you can uninstall some of the conflicted packages, and request a new installation, for instance

sudo apt remove libboost1.74-dev

- ensure all your snaps (application & co) have been upgraded too

sudo snap refresh

- finally, you should check/update/remove all the alternative package source, which were installed on your system (and which were automatically disabled during upgrade), to find them, you can this instruction

sudo find  /etc/apt/sources.list.d/ -iname "*.distUpgrade"

- if you change any such source metadata file, you know the music

sudo apt update && sudo apt upgrade 

That's it, now you can enjoy Ubuntu 24.04.0 LTS, even if you come from version 22.04.4 LTS.