Is it possible to install php-cli for PHP 8.0.1 from the official remote repository, without having to modify my repo list sudo add-apt-repository ppa:ondrej/php?

When I do sudo apt-get upgrade, I have the following message:

 WARNING: PV /dev/sda3 in VG ubuntu-vg is using an old PV header,
 modify the VG to update.

What can I do?

Due to a supposed problem in my Ubuntu 18's packages, I could not upgrade to Ubuntu 20. Instead of checking what was going wrong with all the packages problems, I solved one or two packages problems (I think) and then, even if some problems were still present (I think), I wanted to start the upgrade to Ubuntu 20 (big mistake...!).

The graphical upgrader (or CLI, I don't remember) told me that I was going to do a Partial Upgrade. I clicked on "Continue". Then, I stopped it.

I'm still on Ubuntu 18. So the partial upgrade isn't done I think.

Now when I type: sudo apt-get update/upgrade/dist-upgrade, I get:

The following packages were automatically installed and are no longer required:

(lots of packages)

The following packages will be REMOVED:

(lots of packages)

The following NEW packages will be installed:

(lots of packages)

The following packages will be upgraded:

(lots of packages)

2009 upgraded, 377 newly installed, 104 to remove and 0 not upgraded.

I think all these packages are related to my Partial Upgrade. However I want to cancel my Partial Upgrade. In other words, I don't want to see all these packages. What should I do?

What I've already tried

sudo rm /var/lib/apt/lists/* but it didn't work...

Right after my login session, I would like Ubuntu to execute sudo apt-get update & apt-get dist-upgrade , systematically / automatically. The terminal must be opened so that I can see the output of each of these executions. In particular, I want to be asked to type "y/n" due to the command apt-get dist-upgrade. I don't want to have to type my password : thus, Ubuntu must use it as input of the sudo execution instead of me.

The modifications involved must be independant of any upgrade and migration of Ubuntu.

Question

Which bash file should I edit and in which way ?

Right after my login session, I would like Ubuntu to execute sudo apt-get update & apt-get dist-upgrade , systematically / automatically. The terminal must be opened so that I can see the output of each of these executions. In particular, I want to be asked to type "y/n" due to the command apt-get dist-upgrade. I don't want to have to type my password : thus, Ubuntu must use it as input of the sudo execution instead of me.

The modifications involved must be independant of any upgrade and migration of Ubuntu.

Question

Which bash file should I edit and in which way ?

Edit : Note that it is not yet possible to migrate from 16.04.05 LTS to 18.04.1 LTS. Today is Tuesday, August 7.... The release of 18.04.1 LTS took place on July 26... They must have simply forgotten to enable the "For long-term support versions" option in "Notify me of a new Ubuntu version", in the "Software Updater" options... Someone absolutely must tell them please.

This documentation https://help.ubuntu.com/community/BionicUpgrades indicates, in the part titled "Upgrade from 16.04 or 17.10 to 18.04 > Upgrading Ubuntu Desktops to 18.04 (Recommended)" that in order to migrate from 16.04 (16.04.5 LTS for me) to 18.04 (18.04.1 LTS in fact), we must confirm the "Notify me of a new Ubuntu version:" option is set to "For any new version", and change it if otherwise.

My question is : why not to keep it set at its default value, which is : "For long-term support versions" ? 18.04(.1) is indeed an LTS version ! So this option should also enable the migration.

I have another question: in addition to allowing the change from 16.04(.5) to 18.04(.1), what are/will be the other (potentially bad) consequences of choosing the "For any new version" option, recommended by the above documentation?

Am I making a mistake ?

Important

This migration is really impossible when "For long term support versions" is chosen. It's possible when "For any new version" is chosen.

I would want to install a partition encrypted with AES using a loop-device.

So first, I install the partition and its files system.

1. fdisk /dev/sda
2. mkfs.ext4 /dev/sdaX (with "sdaX" the created partition by fdisk)
3. mount /dev/sdaX <mount_directory>

Then I create text files, images, etc. in mount_directory.

Finally, I use a loop-device.

1. losetup -e aes /dev/loop0 /dev/sda<X>
2. mkfs.ext4 /dev/loop0
3. mount /dev/loop0 <mount_directory>
4. I use <mount_directory> (creation again of files, images, delete them...) but a password will be asked because I encrypted /dev/loop0
5. unmount <mount_directory>
6. losetup -d /dev/loop0