Re: [gentoo-user] kernel panick in 4.2.1 from gentoo-sources

Rich Freeman <rich0@g.o> wrote:

> On Wed, Oct 7, 2015 at 4:13 PM,  <covici@××××××××××.com> wrote:
> > Hi.  I am getting some kind of kernel panick in 4.2.1 -- it boots up OK,
> > ...
> > how
> > do I get any information about what happened -- serial console or other
> > means?  Can I do a console over the network without additional hardware?
>
> That is pretty simple actually.
>
> Set CONFIG_NETCONSOLE=y/m in your kernel config if it is not already set.
> add to your kernel command line:
> netconsole=6666@192.168.0.10/eth0,6666@192.168.0.5/1c:6f:65:ab:07:b2
>
> (The first set of values is port@src-ip/interface.  The second set of
> values is port@dest-ip/MAC.  This is low-level code in the kernel so
> it is just sending raw UDP packets - the routine sending them has no
> idea what your interface IP is, and it can't use ARP.)
>
> On the destination machine, run "nc -u -l -p 6666"
>
> That will listen for console output and dump it to stdout.  You'll get
> everything that goes to dmesg on the remote machine, including
> BUG/PANIC/etc output.  It works fine even if the disks stop syncing.
>
> >
> > The reason I went with that kernel is because I want to try btrfs and
> > they develop fast, so it looked from Google searching that I should be
> > on 4.2 or thereabouts.  The btrfs programs I emerged did say 4.2.
> >
>
> If you're having btrfs issues on such a recent kernel you should
> probably at least run all the backports that are available for it.
>
> There are undoubtedly many btrfs issues in 4.2.1 that have been fixed
> in 4.2.3, so you should probably be running this version if you want
> to stick with 4.2.
>
> Personally, I've been sticking with 3.18 until 4.1 quiets down.  There
> are usually regressions in any new kernel version with btrfs.
>
> > So, I would like to go on two paths at once -- find out about the
> > panick, and maybe go to a lower kernel as well, but I was concerned
> > about btrfs if I do that.  I have not created the pool yet.
>
> Generally speaking the btrfs on-disk format is stable, so for the most
> part you can switch back and forth between versions without issue.  If
> you want to go to a really old kernel series like maybe 3.12 there
> might be a few optional btrfs features that won't work, but in general
> I'd stick with something newer.
>
> So, if you want to be bleeding-edge then stick with the bleeding edge
> and run the latest stable.  If you want something longterm I'd stick
> with the 1st-2nd most recent longterm.  4.1 is still pretty new, but
> I'm close to switching over to it.
>
> You'd need to post the details of the panic to know more - the btrfs
> list is probably the best place.  But again I'd confirm the panic on
> the latest release in the series you're running so as to not waste
> time on issues that may already be fixed.


Thanks much -- 4.2.1 wqas what I just got using gentoo-sources, I will
sync and try again, maybe go to 4.1 and see what happens.  I heard 3.19
was the first version where btrfs actually worked, and I have 3.18 here,
this is why I was trying the newer kernel.  So, what is the latest lts
kernel these days anyway?

Thanks again.

-- 
Your life is like a penny.  You're going to lose it.  The question is:
How do
you spend it?

         John Covici
         covici@××××××××××.com