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I just updated our AWS Linux Server (which uses yum) and a new kernel is installed: kernel-4.1.10-16.27.amzn1.x86_64. It didn't state anything about restarting.

According to this answer here I should see a message that I need to restart:

You don't have to restart the server unless you are getting a message (from yum) that explicitly encourages you to do so.

What does this mean then? No need to reboot? Is this one of those kernels that don't need a restart?

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  • Version 4 has some kernel live patching support. So the question might be how to know whether the kernel has been live patched or not.
    – kasperd
    Oct 22 '15 at 8:54
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    Run uname -r to see what version of kernel you're currently running. If it isn't kernel-4.1.10-16.27.amzn1.x86_64 then you'll need a reboot to pick it up.
    – steve
    Oct 22 '15 at 9:00
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    If you want to use the newly-installed kernel, then reboot the system; if you don't, then don't reboot. Obvious exception is, as stated in your linked Q&A page, if you have ksplice installed/configured or kexec.
    – ILMostro_7
    Oct 22 '15 at 9:18
  • It still running the old version, so it needs a reboot. We don't want to have a new kernel installed without reboot. In case things break, better know now and know what caused it.
    – SPRBRN
    Oct 22 '15 at 10:07
  • For what it's worth, ksplice will not help with a completely different kernel version. ksplice or kgraft (nowadays this has been added directly in kernel) are meant for smaller security fixes or updates to certain modules, not an upgrade to a new major kernel version. kexecwould be the right thing, to load another kernel without rebooting.
    – doktor5000
    Oct 22 '15 at 14:18
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Usually when you install something to Linux, the process only puts some files in several directories or if it is a module you can load it into the kernel without reboot, but if you install another kernel and you want to use it you need to restart and load it at boot time. If you are using grub you can choose between the two kernels installed.

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