windyweather wrote:Installed LM17 Cinnamon a few days ago. Just checked and I can't do the upgrade,
So how do I fix this?
The error is coming up because that file does not exist.
The closest is: linux-libc-dev_3.13.0-24.46_amd64.deb
This means your package list isn't up to date. You'll need to refresh the list ("refresh" on the icon, or "reload" in Synaptic Package Manager).
After that you should see the version I mention above rather than the one your system failed to download.
windyweather wrote:Also, the Shield at the bottom of the screen says the system is up to date, but there are 6 level 5 updates that look like very serious [Red Level 5 Security Updates] that involve the kernel.
The "levels" indicate how risky/new the update is rather than how urgent.
Higher level updates are progressively tested and accordingly updated until they're considered safer and thus fall into lower level updates.
Level 5 security updates aren't the kind that regular users should be too worried about, so they aren't automatically applied.
Your system will be considered up to date if you've installed all of the updates of levels you've specified. (I think it's 1-3 by default)
windyweather wrote:So "go use a terminal to upgrade your kernel" does not compute.
You can install such updates through Synaptic, or change the settings for Mint Update (the shield icon).
It's not a matter of "if you want to upgrade your kernel, use the command line", but if the update isn't marked as "safe", then someone not familiar enough with the OS to abuse the terminal probably wouldn't want to risk an "unsafe" update.
In other words, the absolute newest version of the kernel isn't something that your everyday user should be concerned with. Best to wait until it's been tested thoroughly and undergone necessary revisions.
The main risks to your computer, especially since you're using it for shopping and banking, lie with your browser. Having an up to date browser with extensions like noscript, ABP and ghostery will do more for you than the latest kernel.