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92 lines
3.7 KiB
92 lines
3.7 KiB
6 years ago
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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 Pacemaker cluster environment:
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If we want to use kdump in Pacemaker cluster environment, fence-agents-kdump
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should be installed in every nodes in the cluster. You can achieve this via
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the following 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 are two ways how to configure fence_kdump support:
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1) Pacemaker based clusters
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If you have successfully configured fence_kdump in Pacemaker, there is
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no need to add some special configuration in kdump. So please refer to
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Kexec-Kdump-howto file for more information.
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2) Generic clusters
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For other types of clusters there are two configuration options in
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kdump.conf which enables fence_kdump support:
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fence_kdump_nodes <node(s)>
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Contains list of cluster node(s) separated by space to send
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fence_kdump notification to (this option is mandatory to enable
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fence_kdump)
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fence_kdump_args <arg(s)>
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Command line arguments for fence_kdump_send (it can contain
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all valid arguments except hosts to send notification to)
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These options will most probably be configured by your cluster software,
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so please refer to your cluster documentation how to enable fence_kdump
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support.
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Please be aware that these two ways cannot be combined and 2) has precedence
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over 1). It means that if fence_kdump is configured using fence_kdump_nodes
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and fence_kdump_args options in kdump.conf, Pacemaker configuration is not
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used even if it exists.
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