I checked today if I had any updates that can be applied to my server running Debian Lenny & I noticed that one of the updates was a kernel however the kernel was exactly the same as the one I was booted into /using. Why is it trying to install a kernel I already have on my system? Is this a different revision of the kernel or am I missing something here?

Thanks for any explanation on this.

This is just one more example of how messed-up the "auto updating" paradigm is as a concept.

IMO this is a Windows gimmick evolved in that crippled environment so that Microsoft can retroactively fix all the thousands of mistakes they make when they build their operating systems. Often, at work, I have had customers who have had severe crashes, lockups and incompatibilities suddenly emerge in their Windows installations due to having auto-updates turned on. They receive an update, reboot and hey-presto! Something stops working - or the system doesn't boot at all.

Due to the thousands and thousands of types of configurations and sofware out there, it is notoriously difficult to have "auto updates" that are safe, and that actually work. This seems to be just as true of the Linux world as of the Windows world.

An example is what has happened to you - and your confusion is legitimate. But this is also typical of what happens when you "auto update" - you'll get nonsensical stuff happening (like "upgrading" your kernel to the, golly, same VERSION!) but also less benign stuff that could also potentially break your system.

Auto updating IMO is a gimmick that several Linux distros have started taking up to be more "Windows like" - while this is a manifestation of the very worst aspect of the Windows way of doing things! No wonder it has a detrimental impact, even on the notoriously stable and solid Linux software architecture.

From my experience of using Linux and several packages (LAMP mostly) and developing on it, BE CAREFUL WITH UPDATES OR UPGRADES. The very first thing I do whenever I install a new Linux distro is to turn ANY form of auto updating OFF - at once! If you do not have a compelling reason to upgrade or update something that is working just fine, DON'T. Why attempt to fix something that is not broken?

If you do have to upgrade or update, do it manually - YOU are often smarter and know more about your system than someone who lodges an update on an update service, that, once automatically pulled through to your system, might break your setup.

I also don't really like automatic updates, but I like to be notified, pretty much the way modern distros actually do it by default. They tell you there's something to upgrade and you can then decide what you want to do about it.

In general though I have to disagree with your philosophy of not updating if everything works. Often updates are security-related and thus surely are worth installing.
Also, as for the Debian-kernel. It may not display it, but there surely are changes. It may still be the same kernel-version, but that's how Debian does it. They once choose a kernel and then stick with it, and just provide patches that fix bugs and security-holes.

In my experience, especially concerning Debian, it is usually pretty safe to do updates on a Linux-system.

Seems strange you are using Lenny with the 2.6.18 kernel,that was the original kernel for Etch.
What does cat /etc/debian_version show?

@ rylan76: I have no idea who put the bee in your bonnet, but this is not and auto-update situation. The administrator of the machine (Carlwill) explicitly asked for updates (apt-get dist-upgrade).

More generally, as Reptiler suggests, a kernel upgrade - even to the (allegedly) same version - is often a perfectly valid thing to want to do. It almost certainly means that the kernel has received security patches, and so the kernel number is the same, but if you check carefully, the version number of the .deb will not be.

@ Trooper: Unless you have installed one of the virtual kernel packages (eg, linux-image-2.6-amd64), then even when you upgrade your kernel won't get bumped up to a newer version. Most server admins I know prefer decide for themselves whether or not they want to upgrade a kernel anyhow. So my guess is that Carlwill originally installed the server when it was Etch and then upgraded it to Lenny at some point, but he never upgraded the kernel.

Personally i don't use the virtual package either.
That would explain the 2.6.18 kernel.
I'd still check the version though if it was me.

Same kernel, same revision, different minor revision, most likely a security patch.

Yep a minor revision to your current kernel, check with apt-cache policy to see current revision and proposed/available update