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Reloading a kernel “live” in CentOS / RHEL 6

How can i update kernel on Centos without reboot .?

I found ksplice but it is not supported for Centos.

Regards,

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marked as duplicate by Chris S Mar 7 '12 at 0:46

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KSplice is really the only option. If KSplice doesn't support CentOS or RHEL, you're pretty much out of luck. –  larsks Mar 6 '12 at 20:53
    
CentOS lets you upgrade any time. But you have to reboot to activate the new kernel. What part of the boot-process is actually causing you headaches? –  Nils Mar 6 '12 at 20:55
    
if you need solid uptime, think about using openbsd . You get a lot less kernel updates. –  The Unix Janitor Mar 6 '12 at 22:55
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2 Answers

up vote 3 down vote accepted

From man kexec:

kexec is a system call that enables you to load and boot into another kernel from the currently running kernel. kexec performs the function of the boot loader from within the kernel. The primary difference between a standard system boot and a kexec boot is that the hardware initialization normally performed by the BIOS or firmware (depending on architecture) is not performed during a kexec boot. This has the effect of reducing the time required for a reboot.

To install it: yum install kexec-tools

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It minimize the reboot process. But still there is a down time and not as efficient as KSplice. –  Linuxstartway Mar 6 '12 at 21:42
    
Look at 3dinfluece below. If this is a production server KSplice is not enough to keep the system up to date. BIOS-updates often also require a reboot (as do some other firmware-updates). So there would be better a second server able to take over the sessions. –  Nils Mar 6 '12 at 22:12
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With KSplice not supporting your OS you're out of luck.

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@larsks Centos is not supported by Ksplice at the current time ksplice.com/pricing –  Linuxstartway Mar 6 '12 at 21:07
    
@Nils I want to update the kernel without down time, If i'm using a production server it will be a problem to reboot the server every time i update the kernel. –  Linuxstartway Mar 6 '12 at 21:13
    
The CentOS-Kernel is binary compatible to the RH or unbreakable Linux Kernel. So what? –  Nils Mar 6 '12 at 21:17
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@RamyAllam if uptime is that important then you need to come up with a HA strategy that involves more than one machine with failover. That way you can always take one off line for maintenance. –  3dinfluence Mar 6 '12 at 21:18
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@RamyAllam so you open a direct channel via internet for kernel-updates? I hope these updates are signed (as are RPMs). –  Nils Mar 6 '12 at 22:08
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