Re: [gentoo-user] New kernel does not boot up on remote host

[Dan Farrell]

On Thu, 5 Jul 2007 18:40:20 +0200
Galevsky <galevsky@×××××.com> wrote:

> 2007/7/5, Albert Hopkins <marduk@g.o>:
> > On Thu, 2007-07-05 at 11:36 +0200, Galevsky wrote:
> > > Many thanks for you suggestion. I tried a boot with no fall back,
> > > but nothing added neither to boot.log nor to dmesg. I am sure to
> > > target the right kernel image with no typo into grub.conf . This
> > > new kernel is a =xen-sources-2.6.16.49, and I configured it
> > > making an oldconfig based on current =gentoo-sources-2.6.20
> > > running kernel. So, errors cannot come from drivers or such
> > > things, but specific xen options. Does anyone know any xen option
> > > able to prevent the kernel to boot up ?
> >
> > I guess I (still) don't understand what your issue is.  So I went
> > back and read your original post.  Maybe I misunderstood it.
> >
> >       * What do you mean by "remote host"?
>
> I rent a dedicated host. Thus, I have no physical access to the
> machine. And the reason why I used the fall-back feature into grub is
> to avoid the use of a boring rescue system (via a web interface) to
> take back the control of a not-responding box.
>
> >       * If your box "does not boot" how would you expect to see a
> >         boot.log or dmesg ? They don't exist if the system has not
> >         booted.  In fact "does not boot" implies that you can't
> > even log in to check for dmesg or boot logs.  Perhaps you can
> > explain what it is exactly you mean by "does not boot".
>
> When I try to boot on the new kernel, I set it as the "default" one in
> grub.conf and reboot the box. And I wait for a few minutes. Then I try
> to log on, praying to find the box responding.
>
> First, with grub fall-back activated, the boot had fallen back and I
> was able to read the logs that contained the running kernel logs, but
> no info about the kernel boot that failed. That was the matter of my
> first mail: how to read  the reasons of the first kernel-boot-attempt
> failure.
>
> Secondly, you advised me to turn fall back off. I do. The box is no
> more responding after reboot, and I have to launch the "rescue system"
> to log on my box, and read the /var/log/*. I thought previously that
> some pb happened -I didn't know when exactly-... and was waiting for
> more info in log files. But files were empty. So, I conclude that the
> boot procedure failed (and you too ;o)).
>
> Finally, I have to find out why my kernel is not booting. I tuned up
> well my previous kernel, a gentoo-sources-2.6.20 -this kernel runs
> currently my box very well- and the kernel I want to boot now is a
> xen-sources-2.6.16. I made an oldconfig on /proc/config.gz of the
> 2.6.20 running kernel, and fill in xen-dom0 specific options as
> indicated on the wiki tutorial [1]. So, I guess I did something wrong
> with the dom0 xen config, and asked for advice on xen specific options
> with my second post.
>
> >       * Usually there is an error message on the console if there
> > is a boot loader/kernel issue with booting.
> >       * Also you never posted your grub.conf.
> >
> > So hopefully you can come up with a specific explanation of "does
> > not boot" as well as your config and any console messages you get.
> > Else this becomes a "blind leading the blind" issue.
>
> I have no console message to provide you, I just know that my remote
> box is not responding when I try to boot another kernel (If you know
> the way to get logs, I'll be grateful :o)). And I checked the
> /var/log/* to be sure that the kernel was not running but just missing
> any network feature so that I could not log on the box despite the
> kernel was actually running.
>
> As for my grub.conf + 'ls -l /boot' , I will provide you in a while (I
> need to go home before), but I am not sure it is relevant. (just to
> check for typo I guess).
>
> > --
> > Albert W. Hopkins
> >
> > --
> > gentoo-user@g.o mailing list
>
> Many thanks to take care of my problem :o)
>
> Gal'
>
> [1]: http://gentoo-wiki.com/HOWTO_Xen_and_Gentoo

from /etc/conf.d/rc:
# RC_BOOTLOG will generate a log of the boot messages shown on the
console. # Useful for headless machines or debugging.  You need to
emerge the # app-admin/showconsole package for this to work.  Note that
this probably # won't work correctly with boot splash.

RC_BOOTLOG="no"

I recommend you install showconsole and set RC_BOOTLOG to yes, that
might help you.  It is possible that maybe something as mundane as
networking is failing for a stupid reason, and therefore you cant get
to the computer because it cant finish booting.
-- 
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