[svlug] Booting to different kernel?

[Scott DuBois]

On 06/08/2014 08:13 PM, Karen Shaeffer wrote:
> On Sun, Jun 08, 2014 at 07:25:30PM -0700, Scott DuBois wrote:
>> On 06/07/2014 01:09 PM, Karen Shaeffer wrote:
>>> On Sat, Jun 07, 2014 at 12:00:07AM -0700, crquan wrote:
>>>>
>>>> Yes, you may look /boot/grub/menu.lst and better to change in
>>>> /etc/default/grub (For Ubuntu),
>>>> there you may just change one line GRUB_DEFAULT=... and run
>>>> update-grub to update
>>>> /boot/grub/menu.lst; if you manually change /boot/grub/menu.lst,
>>>> that's not recommended,
>>>> because in future if you update ubuntu, get another kernel will
>>>> overwrite /boot/grub/menu.lst,
>>>> so you'd better to change /etc/default/grub, future kernel upgrades
>>>> would take care of that,
>>>>
>>> --- end quoted text ---
>>>
>>> Hi,
>>> Yes, but that's the difference between someone who is an expert in linux
>>> systems and a casual user. I would definitely prefer to manage my config
>>> files myself. I've been doing that since 1997 and learn far more when some
>>> script messes it up. On the other hand, my point of view isn't applicable
>>> to most users and certainly wasn't best advice to John. In retrospect, I
>>> should have just ignored the call for help and minded my own business.
>>>
>>> enjoy,
>>> Karen
>>>
>>
>> Hmmm, don't know if this would be considered any kind of expert issue
>> unless expert is anyone doing things beyond point-and-click users but,
>> here are a couple of links that reference the material previously mentioned.
>>
> Hi Scott,
> 
> I don't think grub requires too much expertise. It is very simplistic for
> basic booting. You can get quite expert with network booting using pxe,
> for example. I once helped Penguin Computing port Scyld clusterware from
> RHEL4 to RHEL5, where I ported the compute nodes. And their use of pxe
> was quite fun and interesting. The compute nodes were diskless. To run a
> job, you needed to specify what software and resources were needed. And then
> the nodes were booted using a double kernel process, and all the software
> required to run the application was pulled in over the LAN as part of the
> boot process. Using pxe in this environment, booting maybe hundreds or even
> thousands of compute nodes required some expertise.
> 
> I manage my grub config files, because I have been known to run my own custom
> kernels with custom commandline options configured in the grub config files, so
> grub can pass them into the kernel at boot time. Running a stock Ubuntu or RedHat
> kernel has its drawbacks, if you care about optimizing your operating system.
> 
> If you know what you are doing, managing your own grub config files doesn't
> require much more effort than managing the grub user interface scripts, in
> my opinion.
> 
> enjoy,
> Karen
> 
Hi Karen,

Interesting note, thanks for sharing that info.

As each system is different in the performance and use for any given
application, it would make sense that custom tuning one's kernel would
be beneficial until such time a new kernel is released and one would
want to take advantage of the improvements made in the recent release.
Then the management repeats itself to strip the new additions from the
current release and write them into the custom deployment.

If a person has time and the wherewithal to pursue such endeavours, it
would by all means be in that persons best interest to do so to optimize
special deployments. However, it also sounds like a lot of work so the
investment would definitely have to be motivated by special
circumstances. That is unless the deployment case in question is not one
in which recent kernel release modifications are of any real
significance such as some embedded cases.

Custom is good sometimes and not so good sometimes, it all depends on
the long term expectations.

-- 
Scott DuBois
President EBLUG
BSIT Software Engineering
Freenode: Roguehorse