The kernel packagename is linux-image-amd64. This is a virtual package that depends on a kernel package whose name includes the version number.
The kernel version in LMDE is 3.16.something and in jessie-backports is 4.9.something.
First I added /etc/apt/sources.list.d/custom.list with one line for jessie-backports as suggested in that forum posting.
I intentionally omitted the APT pinning because I think the version numbers in jessie-backports should typically [*] be higher than in the default LMDE repositories, so (unless the jessie-backports version of a specific package is found to break something) I think APT should (with the added sources.list.d line) default to the jessie-backports version without needing pinning.
*Furthermore, software (Cinnamon etc.) that's being developed by the Linux Mint project is expected to be at a higher version in the LMDE repos than in jessie-backports, so pinning to jessie-backports would result in an older version of those packages.
Then I clicked "Reload" in Synaptic (the equivalent of "apt-get update"). Almost all packages were then shown with a "Not installed (new in repository)" icon (a star icon). The linux-image-xyz-amd64 packages with 4.x version numbers in their names were now listed in Synaptic. But there were a couple of issues:
- Nothing (no Update Manager type of GUI) prompted me to install any jessie-backports packages.
- Synaptic still shows "Latest Version" of linux-image-amd64 as 3.16.x rather than 4.x.
I then added the /etc/apt/preferences.d/custom.pref APT-pinning paragraph for jessie-backports as given in the forum posting. Once I clicked Synaptic's Reload button, the star icons went away, but the 2 mentioned issues (bulleted list above) remained. I then rebooted and opened Synaptic again, with no change.
In Synaptic's Settings > Preferences > Distribution tab, "Package upgrade behavior" has (throughout the scenario described here) been set to "Always prefer the highest version." As stated near the beginning of this posting, the wording of that option is what I'd like APT to do on this machine. But APT doesn't seem to be doing that.
I don't think I should have to "apt-get install" on a per-package basis as in the 4th code quotation in the referenced forum posting.
Comments will be much appreciated. If this situation warrants a bug report, I'll be happy to copy-and-paste into the appropriate bugtracker.