Planet Ceph

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December 17, 2014

Ceph: collect Kernel RBD logs

{% img center http://sebastien-han.fr/images/ceph-collect-krbd-logs.jpg Ceph: collect Kernel RBD logs %}

Quick tip to collect Kernel RBD logs.

Make sure your kernel is compiled with CONFIG_DYNAMIC_DEBUG (and CONFIG_DEBUG_FS) enabled:

bash
$ sudo cat /boot/config-`uname -r` | grep DYNAMIC_DEBUG
CONFIG_DYNAMIC_DEBUG=y

Then mount debugfs:

bash
$ sudo mount -t debugfs none /sys/kernel/debug

Set the console log level to 9:

bash
$ sudo echo 9 > /proc/sysrq-trigger

Then chose the module that you want to log:

bash
$ sudo echo 'module rbd +p' | sudo tee -a /sys/kernel/debug/dynamic_debug/control

Looking at dmesg will show the corresponding logs.
You can use this script from the Ceph repo as well to enable all of them:

“`bash

!/bin/sh -x

p() {
echo “$*” > /sys/kernel/debug/dynamic_debug/control
}

echo 9 > /proc/sysrq-trigger
p ‘module ceph +p’
p ‘module libceph +p’
p ‘module rbd +p’
“`

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