[CentOS] upgrade question. - when to reboot

Michael Simpson mikie.simpson at gmail.com
Thu Jan 15 10:33:10 UTC 2009


On 1/15/09, Kenneth Burgener <kenneth at mail1.ttak.org> wrote:
> On 1/9/2009 9:49 AM, Robert Nichols wrote:
> If a hard reboot is what you are attempting to avoid, with 'kexec' even
> the Linux kernel can be "reloaded" without a hardware reset.  This is
> convenient if you want to avoid the long system reset time.
>
> "Kexec is a patch to the Linux kernel that allows you to boot directly
> to a new kernel from the currently running one. In the boot sequence
> described above, kexec skips the entire bootloader stage (the first
> part) and directly jumps into the kernel that we want to boot to. There
> is no hardware reset, no firmware operation, and no bootloader involved.
> The weakest link in the boot sequence -- that is, the firmware -- is
> completely avoided. The big gain from this feature is that system
> reboots are now extremely fast. For enterprise-class systems, kexec
> drastically reduces reboot-related system downtime. For kernel and
> system software developers, kexec helps you quickly reboot your system
> during development or testing efforts without having to go through the
> costly firmware stage every time." [1]
>

if you really have to have as perfect an uptime as possible then you
can actually patch a running kernel using ksplice

<http://www.ksplice.com/>

should only be used for critical security updates but useful nonetheless

mike


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