[lxc-users] Getting kdump to work on an LXC server

Rod Bruce rod.bruce at mnsu.edu
Fri Sep 12 12:39:50 UTC 2014

On 09/11/2014 04:07 PM, Serge Hallyn wrote:
> Quoting Rod Bruce (rod.bruce at mnsu.edu):
>> Greetings,
>> I have been working on a problem the last couple of days and I believe I
>> have come up with a solution so I thought I would share it with the list
>> in case anybody else runs into this or someone has a better solution.
>> Problem:
>> I have had a server running Ubuntu 14.04 hang a couple of times. I try
>> to run everything using standard Ubuntu packages. The server is an LXC
>> host with two containers running on it (but several more planned). I
>> wanted to get a kernel core dump if it hung again so I started
>> investigating kdump/kexec. I installed, configured, and tested
>> kdump/kexec on another server and it worked as advertised. However, when
>> I tried it on the LXC server it would save the core dump OK but the
>> server would fail to reboot or hang at some other point in the process.
>> I noticed that when kexec was booting the secondary kernel it was
>> starting up all of the services that start on a normal boot, including
>> LXC, and that seemed to be causing a problem. When I set the containers
> Do you have any idea why it was causing a problem?

I do not.

> Now that you are kexecing into runlevel 2, after you do that, are you
> able to start the lxc service and lxc container by hand?

When kexec kicks off the secondary kernel as part of the kdump process
it writes out the kernel core dump and, when that is finished, the
server reboots. This is the result I was working toward. With this
scenario there is not a chance to start lxc.

I will try to simulate this by kexecing manually into runlevel 2 and
then starting up lxc and report back.

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Rod Bruce
UNIX System and Network Administrator
PALS, A Program of the
Minnesota State Colleges and Universities
rod.bruce at mnsu.edu

Quis custodiet ipsos custodes?

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