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Date: Sun, 26 Feb 2012 02:50:46 +0700
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Subject: Re: [gentoo-user] Re: Safe way to test a new kernel?
From: Pandu Poluan <pandu@poluan.info>
To: gentoo-user@lists.gentoo.org
Cc: emailgrant@gmail.com
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On Feb 26, 2012 2:05 AM, "Robert David" <robert.david.public@gmail.com>
wrote:
>
> V Sat, 25 Feb 2012 10:32:20 -0800
> Grant <emailgrant@gmail.com> naps=C3=A1no:
>
> > >> >> I need to test a kernel config change on a remote system. Is
> > >> >> there a safe way to do this? The fallback thing in grub has
> > >> >> never worked for me. When does that ever work?
> > >> >
> > >> >
> > >> > You can press ESC in the Grub screen and it will take you to
> > >> > text-only mode. There, you select an entry, press "e" and edit
> > >> > it. Press ENTER when you're finished, and then press "b" to boot
> > >> > your modified entry.
> > >> >
> > >> > That way, you can boot whatever kernel you want if the current
> > >> > one doesn't work.
> > >>
> > >> I can't do that remotely though. I'm probably asking for something
> > >> that doesn't exist.
> > >>
> > >> - Grant
> > >>
> > >
> > > Don't do that if you don't have some tool like KVM, or other remote
> > > management of the server. Or if it is available in the data center,
> > > just call them and order this service for the time you need to do
> > > updates.
> > >
> > > This is why I don't use gentoo on servers any more, just because
> > > I rather stay safe than sorry.
> >
> > How is another distro different in this situation?
> >
> > - Grant
>
> Just because when using distros like Centos/RHEL or Debian stable, you
> have very little chance that the kernel released will fail. Due to
> extensive testing, user base and update policy. And major kernel update
> you done only once in few years and the transition is tested before
> release done (though you are supposed to test yourself to be safe).
>
> This is not saying that gentoo is bad, I'm very big fan of gentoo.
> But you have to concern where it use and where not.
>
> Robert.
>
Anecdotal, but...
I once had an Ubuntu VM that can't shutdown after a kernel update. First
boot after update went well, but when I rebooted it again, it pegged its
vCPUs at 100% before I ordered the Xen hypervisor to put it out of its
misery.
The bug was apparently in the portion of the kernel running in the primary
CPU that's responsible for shutting down the other CPUs before cutting the
power. And IIRC, this bug affects all multi-processor configuration.
So, as you can see, binary distros can still fuck up royal time. Not to
mention that if you have an exotic configuration, support for your
configuration might not be built into the kernel by the distro.
Somehow I believe people deploying Gentoo servers will be much more
careful...
Rgds,
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Content-Type: text/html; charset=UTF-8
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<p><br>
On Feb 26, 2012 2:05 AM, "Robert David" <<a href=3D"mailto:rob=
ert.david.public@gmail.com">robert.david.public@gmail.com</a>> wrote:<br=
>
><br>
> V Sat, 25 Feb 2012 10:32:20 -0800<br>
> Grant <<a href=3D"mailto:emailgrant@gmail.com">emailgrant@gmail.com=
</a>> naps=C3=A1no:<br>
><br>
> > >> >> I need to test a kernel config change on a remo=
te system. =C2=A0Is<br>
> > >> >> there a safe way to do this? =C2=A0The fallback=
thing in grub has<br>
> > >> >> never worked for me. =C2=A0When does that ever =
work?<br>
> > >> ><br>
> > >> ><br>
> > >> > You can press ESC in the Grub screen and it will ta=
ke you to<br>
> > >> > text-only mode. There, you select an entry, press &=
quot;e" and edit<br>
> > >> > it. Press ENTER when you're finished, and then =
press "b" to boot<br>
> > >> > your modified entry.<br>
> > >> ><br>
> > >> > That way, you can boot whatever kernel you want if =
the current<br>
> > >> > one doesn't work.<br>
> > >><br>
> > >> I can't do that remotely though. =C2=A0I'm proba=
bly asking for something<br>
> > >> that doesn't exist.<br>
> > >><br>
> > >> - Grant<br>
> > >><br>
> > ><br>
> > > Don't do that if you don't have some tool like KVM, =
or other remote<br>
> > > management of the server. Or if it is available in the data =
center,<br>
> > > just call them and order this service for the time you need =
to do<br>
> > > updates.<br>
> > ><br>
> > > This is why I don't use gentoo on servers any more, just=
because<br>
> > > I rather stay safe than sorry.<br>
> ><br>
> > How is another distro different in this situation?<br>
> ><br>
> > - Grant<br>
><br>
> Just because when using distros like Centos/RHEL or Debian stable, you=
<br>
> have very little chance that the kernel released will fail. Due to<br>
> extensive testing, user base and update policy. And major kernel updat=
e<br>
> you done only once in few years and the transition is tested before<br=
>
> release done (though you are supposed to test yourself to be safe).<br=
>
><br>
> This is not saying that gentoo is bad, I'm very big fan of gentoo.=
<br>
> But you have to concern where it use and where not.<br>
><br>
> Robert.<br>
></p>
<p>Anecdotal, but... </p>
<p>I once had an Ubuntu VM that can't shutdown after a kernel update. F=
irst boot after update went well, but when I rebooted it again, it pegged i=
ts vCPUs at 100% before I ordered the Xen hypervisor to put it out of its m=
isery.</p>
<p>The bug was apparently in the portion of the kernel running in the prima=
ry CPU that's responsible for shutting down the other CPUs before cutti=
ng the power. And IIRC, this bug affects all multi-processor configuration.=
</p>
<p>So, as you can see, binary distros can still fuck up royal time. Not to =
mention that if you have an exotic configuration, support for your configur=
ation might not be built into the kernel by the distro.</p>
<p>Somehow I believe people deploying Gentoo servers will be much more care=
ful... </p>
<p>Rgds, <br>
</p>
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