https://help.ubuntu.com/community/Lubuntu/Documentation/RemoveOldKernels

[Jarno Suni]

The page is currently immutable. Few remarks concerning the page:

-it is not Lubuntu specific information. I think only the way how to
 launch Software & Updates may vary between flavors.

- Please note that autoremove does not work with manually installed
kernels. Kernels installed using update manager may be marked as
manually installed; see
https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1492709


- Also, due to https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1440608
autoremove may remove too many kernels leaving only one, which some may
find too few.

- It is also worth noting that the Automatic Maintenance does not purge
the kernels, but only removes them. So `dpkg -l` lists them as "rc".

As for "Safely removing old kernels" chapter, in the example there are listed solely
linux-image-extra-<version>-<type> packages. Purging one does not purge
respective linux-image-<version>-<type> package, nor does it remove
respective header packages. I suppose `dpkg -l | grep linux-image`
lists linux-image-<version>-<type> packages, too, but that is not
visible in the page.

- Purging say 4.2.0-18-generic kernel including unneeded headers
completely consists of purging at least
linux-image-4.2.0-18-generic
linux-headers-4.2.0-18-generic
and if not other package, such as linux-headers-4.2.0-18-lowlatency,
depending on the following is installed, purge also
linux-headers-4.2.0-18
(You do not have to purge linux-image-extra-4.2.0-18-generic separately,
as it is removed due to its dependency on linux-image-4.2.0-18-generic.)

 
-- 
Jarno Suni - http://iki.fi/8/