[CentOS] upgrade question. - when to reboot

Kenneth Burgener kenneth at mail1.ttak.org
Thu Jan 15 05:13:35 UTC 2009


On 1/9/2009 9:49 AM, Robert Nichols wrote:
> Brian wrote:
>   
>> Is there a list of packages that after update require a reboot, other then kernel?
>>     
> For updates other than the kernel, there is almost always an answer
> short of a full reboot.  But, finding that answer and being 100%
> certain that it is a complete answer can be a challenge, and is,
> say, bringing the system down to single-user mode momentarily all
> that much better than simply rebooting?

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]


Kenneth

[1] http://www.ibm.com/developerworks/linux/library/l-kexec.html



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