Question about upgrade and autoremove in the terminal

[life0riley]

I've always wondered about this but never got around to asking the question. So here goes...

My example comes from Kubuntu 26.04. The behavior is the same in Kubuntu 26.10 and other versions I have tried recently to my memory.

I update Kubuntu in the terminal 'sudo apt update' followed by 'sudo apt full-upgrade'

The first time running 'sudo apt update' followed by 'sudo apt full-upgrade'.
The kernel and modules are updated

I reboot.

The second time running 'sudo apt update' followed by 'sudo apt full-upgrade' the following are removed:
REMOVING:
linux-headers-7.0.0-38-generic linux-main-modules-zfs-7.0.0-38-generic linux-modules-nvidia-580-7.0.0-38-generic linux-signatures-nvidia-7.0.0-38-generic
linux-image-7.0.0-38-generic linux-modules-7.0.0-38-generic linux-objects-nvidia-580-7.0.0-38-generic linux-tools-7.0.0-38-generic

I reboot.

When I run 'sudo apt autoremove', the following are removed:
REMOVING:
linux-headers-7.0.0-38 linux-tools-7.0.0-38

Is there a reason why everything, kernel headers, image, ...etc. are not removed all at once the next time I run sudo apt full-upgrade or sudo apt autoremove?

[boospy33]

Hmm... good question. Maybe the headers are needed to decompile something, a kernel module, perhaps?
Try this: Manually uninstall the kernel, including the headers. What I mean is, when `autoremove` tries to remove the kernel but not the headers, run `apt remove` to remove the kernel and the headers together. Does the system allow that?
If yes, it wouldn't make sense for the system to not remove the headers right away with the first autoremove.

[die.boer]

this is normal APT behaviour. It can happen because of package dependencies and the order in which packages become unused.
The main kernel packages are removed during the next full-upgrade. Once those packages are gone, some related packages, such as:
linux-headers-7.0.0-38
linux-tools-7.0.0-38
may then become orphaned — meaning nothing installed requires them anymore. They are consequently picked up the next time sudo apt autoremove is run.
So APT isn't necessarily forgetting them. Removing one group of packages can make another group eligible for autoremove.

[claydoh]

Ubuntu configures apt to keep 3 kernel versions, and uninstalls the extra when there is a new one. This is not an auto remove operation.

I can't say why it isn't set to uninstall *all* the peripheral packages, but it may be that not everyone has all of these present, or they can be of use in some cases outside of actually running the associated kernel version.

[life0riley]

Thankyou all for the replies. It makes sense to me now.

I tried mixing up the order to see what I get.

Here I tried autoremove right after updating the kernels and rebooting:

$ sudo apt autoremove
[sudo: authenticate] Password:
REMOVING:
linux-headers-7.0.0-28 linux-image-7.0.0-28-generic linux-modules-7.0.0-28-generic linux-tools-7.0.0-28-generic
linux-headers-7.0.0-28-generic linux-main-modules-zfs-7.0.0-28-generic linux-tools-7.0.0-28

Summary:
Upgrading: 0, Installing: 0, Removing: 7, Not Upgrading: 4
Freed space: 319 MB

Continue? [Y/n] n
Abort.
$

Here I tried full-upgrade before autoremove immediately after updating the kernels and rebooting:

$ sudo apt full-upgrade
The following packages were automatically installed and are no longer required:
linux-headers-7.0.0-28 linux-tools-7.0.0-28
Use 'sudo apt autoremove' to remove them.

Get more security updates through Ubuntu Pro with 'esm-apps' enabled:
libtesseract5 libsrt1.5-gnutls libass9 libavdevice62 ffmpeg
libopenexr-3-1-30 libavcodec62 gocryptfs libavfilter11 libavutil60
libswscale9 libswresample6 libavformat62 tesseract-ocr libde265-0
Learn more about Ubuntu Pro at https://ubuntu.com/pro
Not upgrading yet due to phasing:
drkonqi python3-software-properties software-properties-common software-properties-qt

REMOVING:
linux-headers-7.0.0-28-generic linux-image-7.0.0-28-generic linux-main-modules-zfs-7.0.0-28-generic linux-modules-7.0.0-28-generic linux-tools-7.0.0-28-generic

Summary:
Upgrading: 0, Installing: 0, Removing: 5, Not Upgrading: 4
Freed space: 220 MB

Continue? [Y/n] n
Abort.
$

This all makes sense now.

This is the list of installed kernels before the next update or autoremove after new kernels are installed:

$ apt list --installed | grep linux-image

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

linux-image-7.0.0-28-generic/resolute-updates,resolute-security,now 7.0.0-28.28 amd64 [installed,auto-removable]
linux-image-7.0.0-31-generic/resolute-updates,resolute-security,now 7.0.0-31.31 amd64 [installed,automatic]
linux-image-7.0.0-43-generic/resolute-updates,now 7.0.0-43.43 amd64 [installed,automatic]
linux-image-generic/resolute-updates,now 7.0.0-43.43 amd64 [installed,automatic]
$

This is the list of installed kernels after the next update or autoremove before new kernels are installed:

$ apt list --installed | grep linux-image

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

linux-image-7.0.0-42-generic/resolute-updates,resolute-security,now 7.0.0-42.42 amd64 [installed,automatic]
linux-image-7.0.0-43-generic/resolute-updates,now 7.0.0-43.43 amd64 [installed,automatic]
linux-image-generic/resolute-updates,now 7.0.0-43.43 amd64 [installed,automatic]
$

Ubuntu keeps three kernels with the oldest marked [installed,auto-removable] if I don't run autoremove before the next update.