Ubuntu upgrades - dealing with things that don't get upgraded

Doing an upgrade on an Ubuntu 18.04 boxen: - 

apt-get upgrade

...

Calculating upgrade... Done

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

  linux-headers-4.15.0-112 linux-headers-4.15.0-112-generic linux-image-4.15.0-112-generic linux-modules-4.15.0-112-generic linux-modules-extra-4.15.0-112-generic

Use 'apt autoremove' to remove them.

The following packages have been kept back:

  base-files libgl1-mesa-dri linux-generic linux-headers-generic linux-image-generic netplan.io ubuntu-server

0 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.

...

I wondered how to handle the "kept back" warning ....

Wonder no more ....

apt-get --with-new-pkgs upgrade

...

Searching for splash image ... none found, skipping ...

Found kernel: /boot/vmlinuz-4.15.0-118-generic

Found kernel: /boot/vmlinuz-4.15.0-117-generic

Found kernel: /boot/vmlinuz-4.15.0-122-generic

Found kernel: /boot/vmlinuz-4.15.0-118-generic

Found kernel: /boot/vmlinuz-4.15.0-117-generic

Replacing config file /run/grub/menu.lst with new version

Updating /boot/grub/menu.lst ... done

/etc/kernel/postinst.d/zz-update-grub:

Sourcing file `/etc/default/grub'

Generating grub configuration file ...

Found linux image: /boot/vmlinuz-4.15.0-122-generic

Found initrd image: /boot/initrd.img-4.15.0-122-generic

Found linux image: /boot/vmlinuz-4.15.0-118-generic

Found initrd image: /boot/initrd.img-4.15.0-118-generic

Found linux image: /boot/vmlinuz-4.15.0-117-generic

Found initrd image: /boot/initrd.img-4.15.0-117-generic

done

Processing triggers for initramfs-tools (0.130ubuntu3.11) ...

update-initramfs: Generating /boot/initrd.img-4.15.0-122-generic

...

plus: -

apt autoremove

to get rid of any excess baggage.

Source: “The following packages have been kept back:” Why and how do I solve it?