Current File : //usr/share/doc/kexec-tools-2.0.15/kdump-in-cluster-environment.txt
Kdump-in-cluster-environment HOWTO
Introduction
Kdump is a kexec based crash dumping mechansim for Linux. This docuement
illustrate how to configure kdump in cluster environment to allow the kdump
crash recovery service complete without being preempted by traditional power
fencing methods.
Overview
Kexec/Kdump
Details about Kexec/Kdump are available in Kexec-Kdump-howto file and will not
be described here.
fence_kdump
fence_kdump is an I/O fencing agent to be used with the kdump crash recovery
service. When the fence_kdump agent is invoked, it will listen for a message
from the failed node that acknowledges that the failed node is executing the
kdump crash kernel. Note that fence_kdump is not a replacement for traditional
fencing methods. The fence_kdump agent can only detect that a node has entered
the kdump crash recovery service. This allows the kdump crash recovery service
complete without being preempted by traditional power fencing methods.
fence_kdump_send
fence_kdump_send is a utility used to send messages that acknowledge that the
node itself has entered the kdump crash recovery service. The fence_kdump_send
utility is typically run in the kdump kernel after a cluster node has
encountered a kernel panic. Once the cluster node has entered the kdump crash
recovery service, fence_kdump_send will periodically send messages to all
cluster nodes. When the fence_kdump agent receives a valid message from the
failed nodes, fencing is complete.
How to configure Pacemaker cluster environment:
If we want to use kdump in Pacemaker cluster environment, fence-agents-kdump
should be installed in every nodes in the cluster. You can achieve this via
the following command:
# yum install -y fence-agents-kdump
Next is to add kdump_fence to the cluster. Assuming that the cluster consists
of three nodes, they are node1, node2 and node3, and use Pacemaker to perform
resource management and pcs as cli configuration tool.
With pcs it is easy to add a stonith resource to the cluster. For example, add
a stonith resource named mykdumpfence with fence type of fence_kdump via the
following commands:
# pcs stonith create mykdumpfence fence_kdump \
pcmk_host_check=static-list pcmk_host_list="node1 node2 node3"
# pcs stonith update mykdumpfence pcmk_monitor_action=metadata --force
# pcs stonith update mykdumpfence pcmk_status_action=metadata --force
# pcs stonith update mykdumpfence pcmk_reboot_action=off --force
Then enable stonith
# pcs property set stonith-enabled=true
How to configure kdump:
Actually there are two ways how to configure fence_kdump support:
1) Pacemaker based clusters
If you have successfully configured fence_kdump in Pacemaker, there is
no need to add some special configuration in kdump. So please refer to
Kexec-Kdump-howto file for more information.
2) Generic clusters
For other types of clusters there are two configuration options in
kdump.conf which enables fence_kdump support:
fence_kdump_nodes <node(s)>
Contains list of cluster node(s) separated by space to send
fence_kdump notification to (this option is mandatory to enable
fence_kdump)
fence_kdump_args <arg(s)>
Command line arguments for fence_kdump_send (it can contain
all valid arguments except hosts to send notification to)
These options will most probably be configured by your cluster software,
so please refer to your cluster documentation how to enable fence_kdump
support.
Please be aware that these two ways cannot be combined and 2) has precedence
over 1). It means that if fence_kdump is configured using fence_kdump_nodes
and fence_kdump_args options in kdump.conf, Pacemaker configuration is not
used even if it exists.
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