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Kdump-in-cluster-environment HOWTO
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Introduction
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Kdump is a kexec based crash dumping mechansim for Linux. This docuement
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illustrate how to configure kdump in cluster environment to allow the kdump
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crash recovery service complete without being preempted by traditional power
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fencing methods.
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Overview
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Kexec/Kdump
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Details about Kexec/Kdump are available in Kexec-Kdump-howto file and will not
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be described here.
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fence_kdump
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fence_kdump is an I/O fencing agent to be used with the kdump crash recovery
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service. When the fence_kdump agent is invoked, it will listen for a message
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from the failed node that acknowledges that the failed node is executing the
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kdump crash kernel. Note that fence_kdump is not a replacement for traditional
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fencing methods. The fence_kdump agent can only detect that a node has entered
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the kdump crash recovery service. This allows the kdump crash recovery service
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complete without being preempted by traditional power fencing methods.
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fence_kdump_send
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fence_kdump_send is a utility used to send messages that acknowledge that the
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node itself has entered the kdump crash recovery service. The fence_kdump_send
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utility is typically run in the kdump kernel after a cluster node has
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encountered a kernel panic. Once the cluster node has entered the kdump crash
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recovery service, fence_kdump_send will periodically send messages to all
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cluster nodes. When the fence_kdump agent receives a valid message from the
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failed nodes, fencing is complete.
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How to configure cluster environment:
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If we want to use kdump in cluster environment, fence-agents-kdump should be
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installed in every nodes in the cluster. You can achieve this via the following
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command:
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# yum install -y fence-agents-kdump
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Next is to add kdump_fence to the cluster. Assuming that the cluster consists
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of three nodes, they are node1, node2 and node3, and use Pacemaker to perform
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resource management and pcs as cli configuration tool.
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With pcs it is easy to add a stonith resource to the cluster. For example, add
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a stonith resource named mykdumpfence with fence type of fence_kdump via the
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following commands:
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# pcs stonith create mykdumpfence fence_kdump \
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pcmk_host_check=static-list pcmk_host_list="node1 node2 node3"
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# pcs stonith update mykdumpfence pcmk_monitor_action=metadata --force
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# pcs stonith update mykdumpfence pcmk_status_action=metadata --force
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# pcs stonith update mykdumpfence pcmk_reboot_action=off --force
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Then enable stonith
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# pcs property set stonith-enabled=true
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How to configure kdump:
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Actually there is nothing special in configuration between normal kdump and
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cluster environment kdump. So please refer to Kexec-Kdump-howto file for more
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information.
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