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I noticed that the date of the currenlty installed Linux kernel Revision/Version is later than the System's install date.

  • 2.6.32-24-generic # /var/log/installer/syslog
  • 2.6.32-25-generic # uname -r

These figures seem to answer my own question, but what surprises me is that I don't remember a dramatic "You must reboot Windows now!" dialog, which I've grown to expect for such a deep system change...

Maybe I just clicked OK ..Windows style :)

Is the kernel somehow able to "replace" itself? ... or maybe it can only do "minor surgery"?

eg. Could I still be running "Lucid" in 2020 with each "latest" kernel being installed via updates. (I'm not going to do that; it's just a test scenario.)

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3 Answers 3

up vote 11 down vote accepted

There is a system called ksplice which allows kernel upgrades without restarting, but Ubuntu isn't using it yet and it's a system most attractive to server admins at the moment.

Any time you have a new kernel update which is made available in the software center updates, you will need to restart the computer in order to make use of the fixed security or other bugs. Each kernel version is separate, so keeping your machine running on the existing kernel won't be harmful unless you count potentially security holes. See also this existing question:

Why not include something like Ksplice so there is no need to reboot after updating?

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Thanks... Now that I've' had time to think about this issue, I do recall one(?) time when I was asked to reboot... I was a bit surprised because all updates and new installs had been seamless before that... That was probaly the time the kernel was upgraded... The rebootless system you mentioned is a nice feature.. not critical for a home desktop, but a great idea for any commercial setting... Maybe it will be standard soon, as the comepetitive bar gets higher. –  Peter.O Nov 3 '10 at 4:26

eg. Could I still be running "Lucid" in 2020 with each "latest" kernel being installed via updates. (I'm not going to do that; it's just a test scenario.)

The name "lucid" is really just the name of the distribution. Yes, in theory (and to some extent in practice) you can keep "lucid" till 2020, its just that you will be upgrading all the components in your system.

Upgrading just the kernel itself (and nothing else) works for sometime, but when there is a major kernel change it will be necessary to change / upgrade other programs also or they wont work anymore.

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Thanks for addressing that point so clearly.. –  Peter.O Nov 3 '10 at 4:28

In-place kernel updates were discussed in this question: Why not include something like Ksplice so there is no need to reboot after updating?

As for the reminder to reboot, see the /etc/motd file for servers when you log in:

Linux terra 2.6.35-22-generic #34-Ubuntu SMP Sun Oct 10 09:24:00 UTC 2010 i686 GNU/Linux
Ubuntu 10.10

Welcome to Ubuntu!
 * Documentation:  https://help.ubuntu.com/

*** System restart required ***
Last login: Tue Nov  2 17:33:22 2010 from ...

and the panel notifier reminder for desktop:

alt text

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Thanks KC.. The system link in the accepted answer actually links to KSplice ;) .. but it's not all that important to me; I'll wailt until it is "standard-issue"... The main point of my question was to understand how kernal updates work. –  Peter.O Nov 3 '10 at 7:19

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