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* [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12
@ 2017-08-19 18:28 Ralph Seichter
  2017-08-19 22:15 ` Craig MacKinder
  2017-08-20  6:17 ` Neil Bothwick
  0 siblings, 2 replies; 15+ messages in thread
From: Ralph Seichter @ 2017-08-19 18:28 UTC (permalink / raw
  To: Gentoo User

It seems strange to me as I write it, but since I updated one of my
virtual servers from Kernel version 4.9.34 to 4.12.5, the server (Gentoo
Linux running as a KVM guest) is experiencing timeouts when trying to
connect to DNS resolvers. For the Kernel update, I followed the same
steps I used for years, like

  cd /usr/src/linux
  zcat /proc/config.gz >.config
  make silentoldconfig (answering "no" whereever possible)
  make ...

After booting with Kernel 4.12, commands like "dig +trace www.ibm.com"
work just fine for a while, duration depending on server load, but after
some threshold is passed, all further attempts to contact resolvers fail
due to timeouts.

I have tried running a local, caching resolver (BIND 9) on the server,
like I usually do, and also tried using the hoster's dedicated resolvers.
With Kernel 4.12, I see timeouts in both cases. These problems do not
occur when I boot with the 4.9 Kernel which I have been using for the
past two months.

It is also worth noting that I updated two other servers to Kernel 4.12
without any issues, but these are "real" servers, not VMs. At this point
I am searching for ways to debug the issue, vaguely suspecting some KVM
magic behind it (without any proof). I know that Kernel 4.11 introduced
several KVM related changes, but that's about it.

I appreciate all pointers.

-Ralph


^ permalink raw reply	[flat|nested] 15+ messages in thread

end of thread, other threads:[~2017-08-23  3:21 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-08-19 18:28 [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12 Ralph Seichter
2017-08-19 22:15 ` Craig MacKinder
2017-08-19 23:14   ` Ralph Seichter
2017-08-20  6:17 ` Neil Bothwick
2017-08-20 12:25   ` Ralph Seichter
2017-08-21  6:08     ` Neil Bothwick
2017-08-21 10:35       ` Ralph Seichter
2017-08-21 11:49         ` [gentoo-user] install under centos606 mad.scientist.at.large
2017-08-21 12:08           ` Ralph Seichter
2017-08-23  3:18             ` R0b0t1
2017-08-21 13:03           ` Zhu Sha Zang
2017-08-21 19:18           ` Mick
2017-08-22  5:21           ` Stroller
2017-08-23  3:21           ` R0b0t1
2017-08-21 18:29         ` [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12 Mick

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