Discussion:
Reboot-less Computers
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Jayesh Badwaik via arch-general
2018-10-28 16:43:28 UTC
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Hi,

I am looking at possibilities to have a setup which does not need to be
restarted at all and can be live patched. I have seen this old post:

http://allanmcrae.com/2015/03/updating-arch-kernel-on-digital-ocean/

And I am reading information about kpatch. But there does not need to be much
information. Is there a reliable way to do this currently? If yes, I would
like to know some information about it.

Ideally, a tried and tested set of steps will be welcome. But things are never
so easy I guess.
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Cheers
Jayesh Badwaik
https://jayeshbadwaik.github.io
Jelle van der Waa
2018-10-28 20:17:31 UTC
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Post by Jayesh Badwaik via arch-general
Hi,
I am looking at possibilities to have a setup which does not need to be
http://allanmcrae.com/2015/03/updating-arch-kernel-on-digital-ocean/
And I am reading information about kpatch. But there does not need to be much
information. Is there a reliable way to do this currently? If yes, I would
like to know some information about it.
The wiki has an article about kpatch, but note that you will have to
maintain your own kernel then. Also kpatch is really geared to updating
your kernel for security issues and not updating to a newer version. [1]

[1] https://wiki.archlinux.org/index.php/Kernel_live_patching
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Jelle van der Waa
Jayesh Badwaik via arch-general
2018-10-28 21:23:35 UTC
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Post by Jelle van der Waa
The wiki has an article about kpatch, but note that you will have to
maintain your own kernel then. Also kpatch is really geared to updating
your kernel for security issues and not updating to a newer version. [1]
[1] https://wiki.archlinux.org/index.php/Kernel_live_patching
Thank you. What are the opinions about kexec? The wiki says
" Note that kexec may not work correctly for you due to devices not fully re-
initializing when using this method, however this is rarely the case. "

https://wiki.archlinux.org/index.php/Kexec
--
Jayesh Badwaik
https://jayeshbadwaik.github.io
Giancarlo Razzolini via arch-general
2018-10-28 21:31:36 UTC
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Post by Jayesh Badwaik via arch-general
Thank you. What are the opinions about kexec? The wiki says
" Note that kexec may not work correctly for you due to devices not fully re-
initializing when using this method, however this is rarely the case. "
https://wiki.archlinux.org/index.php/Kexec
kexec should work just fine on recent hardware. I think the last time I used it,
I had one issue with nvidia, but having bbswitch fixed it. Keep in mind that kexec
is a soft-soft reboot, so, it's not like you're not rebooting the machine. And, in
some cases it might be faster and safer to actually reboot the machine.

Regards,
Giancarlo Razzolini
Florian Pritz via arch-general
2018-10-28 22:47:43 UTC
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Post by Jayesh Badwaik via arch-general
I am looking at possibilities to have a setup which does not need to be
I think that if your system is important enough that it shall never go
down even for a few minutes, what you really want is additional
redundancy in form of a high availability setup. Your hardware and
software can fail at any time and then it doesn't matter if you can
hotpatch your kernel or not. If you have a HA system, it doesn't matter
if you reboot or not because the other node(s) take(s) care of the work
for the time being.

Also sometimes the power fails and if you don't reboot your machines
regularly, they may not come back on after that (ask any bigger data
center). If you reboot regularly, chances are higher that you spread out
any problems and resolve them before all machines are rebooted at once.

If you want to do it for science, all I can say is that I think there are
more interesting/important problems than this, but YMMV.

Well, and then there's the issue that you need to specifically create
the patches and that you can't patch everything because that's just way
too much work, but that has already been mentioned by others in this
thread.

Florian

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