FENCE_AGENT(8)

🌸 FENCE_AGENT(8) — the kdump fencing situation 💅

okay bestie, gather round, because this is FENCE_AGENT(8) from the System Manager's Manual and we're about to make fencing make sense. ✨

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👑 NAME

fence_kdump — fencing agent for use with kdump crash recovery service

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💖 DESCRIPTION

So, fence_kdump is an I/O fencing agent meant to be used with the kdump crash recovery service. When the fence_kdump agent gets invoked, it literally just sits there and listens for a message from the failed node — a message that acknowledges the failed node is out here executing the kdump crash kernel. 🫶

ngl, important: fence_kdump is not a replacement for traditional fencing methods. It can only detect that a node has entered the kdump crash recovery service. That's it, that's the whole job.

But that's actually the point, because it lets the kdump crash recovery service complete without getting preempted by traditional power fencing methods. slay. 💅

Note: the "off" action listens for a message from the failed node that acknowledges the node has entered the kdump crash recovery service. If a valid message comes through from the failed node, the node is considered to be fenced and the agent returns success. But if no valid message arrives from the failed node within the given timeout period? That results in fencing failure. 😭 And when multiple node names / IP addresses are specified, a single valid message is sufficient for success — which is super useful when a single node can send a message via several different IP addresses. 🌈

Also! The fence agent accepts options on the command line and from stdin. Fenced sends parameters through stdin when it execs the agent. And you can run the agent by itself with command line options — which is lowkey so useful for testing and for turning outlets on or off from scripts. 🎀

Vendor URL: http://www.kernel.org/pub/linux/utils/kernel/kexec/

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✨ PARAMETERS ✨

• -n, --nodename=NODE[,NODE...] — a list of names or IP addresses of the node to be fenced. This one is required for the "off" action. You can pass multiple values separated by commas. All values have to be of the same IP network family, no mixing bestie. 🦋
• -p, --ipport=PORT — the IP port number that the fence_kdump agent will use to listen for messages. (Default Value: 7410)
• -f, --family=FAMILY — the IP network family. This forces the fence_kdump agent to use a specific family. The value for FAMILY can be "auto", "ipv4", or "ipv6". (Default Value: auto)
• -o, --action=ACTION — the fencing action to perform. The value for ACTION can be either "off" or "metadata". (Default Value: off)
• -t, --timeout=TIMEOUT — the number of seconds to wait for a message from the failed node. If no message is received within TIMEOUT seconds, the fence_kdump agent returns failure. (Default Value: 60)
• -v, --verbose — print verbose output
• -V, --version — print version
• -h, --help — print usage

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🎀 ACTIONS 🎀

• off — power off machine.
• monitor — check the health of fence device
• metadata — display the XML metadata describing this resource.
• validate-all — validate if all required parameters are entered.

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🦋 STDIN PARAMETERS 🦋

• nodename — list of names or IP addresses of node to be fenced. This option is required for the "off" action. Multiple values separated by commas can be specified. All values must be of same IP network family.
• ipport — IP port number that the fence_kdump agent will use to listen for messages. (Default Value: 7410)
• family — IP network family. Force the fence_kdump agent to use a specific family. The value for FAMILY can be "auto", "ipv4", or "ipv6". (Default Value: auto)
• action — fencing action to perform. The value for ACTION can be either "off" or "metadata". (Default Value: off)
• timeout — number of seconds to wait for message from failed node. If no message is received within TIMEOUT seconds, the fence_kdump agent returns failure. (Default Value: 60)
• verbose — print verbose output
• version — print version
• usage — print usage

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okay and that's the whole page, periodt. 💜 this lil icon is fence_kdump (Fence Agent) and it's been serving since 2009-10-20, still in FENCE_AGENT(8) where it belongs. go forth and fence responsibly, bestie 🫶✨🌸