FENCE_AGENT(8)

💖 FENCE_AGENT(8) 💖

okay bestie, welcome to the manual page for fence_mpath, and yes it lives in section 8 of the System Manager's Manual, we love a classic 🎀

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✨ NAME ✨

fence_mpath — Fence agent for multipath persistent reservation 🦋

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🌸 DESCRIPTION 🌸

So. fence_mpath is an I/O Fencing agent that uses SCSI-3 persistent reservations to control access to multipath devices. The way that it works is honestly iconic.

Underlying devices must support SCSI-3 persistent reservations (that's SPC-3 or greater, no cap) and they also have to support the "preempt-and-abort" subcommand. Both. Not optional. 💅

Here's the vibe: fence_mpath works by having a unique key for each node, and that key has to be set in /etc/multipath.conf. Once registered, a single node will become the reservation holder by creating a "write exclusive, registrants only" reservation on the device(s). The result? Only registered nodes may write to the device(s). periodt.

When a node failure occurs, the fence_mpath agent will remove the key belonging to the failed node from the device(s). The failed node will no longer be able to write to the device(s). A manual reboot is required. 😭

When used as a watchdog device you can define e.g. retry=1, retry-sleep=2 and verbose=yes parameters in /etc/sysconfig/stonith if you have issues with it failing. (just a lil tip from the original, not me being dramatic, it's literally in there 🫶)

The fence agent accepts options on the command line as well as from stdin. Fenced sends parameters through stdin when it execs the agent. The agent can be run by itself with command line options — this is useful for testing and for turning outlets on or off from scripts. slay for scripting honestly ✨

Vendor URL: https://www.sourceware.org/dm/

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🌈 PARAMETERS 🌈

• -o, --action=[action] — Fencing action (Default Value: off)
• -d, --devices=[devices] — List of devices to use for current operation. Devices can be comma or space separated list of device-mapper multipath devices (eg. /dev/mapper/3600508b400105df70000e00000ac0000 or /dev/mapper/mpath1). Each device must support SCSI-3 persistent reservations.
• -k, --key=[key] — Replaced by port/-n/--plug
• -n, --plug=[key] — Key to use for the current operation. This key should be unique to a node and have to be written in /etc/multipath.conf. For the "on" action, the key specifies the key use to register the local node. For the "off" action, this key specifies the key to be removed from the device(s).
• --suppress-errors — Error log suppression.
• -q, --quiet — Disable logging to stderr. Does not affect --verbose or --debug-file or logging to syslog.
• -v, --verbose — Verbose mode. Multiple -v flags can be stacked on the command line (e.g., -vvv) to increase verbosity.
• --verbose-level — Level of debugging detail in output. Defaults to the number of --verbose flags specified on the command line, or to 1 if verbose=1 in a stonith device configuration (i.e., on stdin).
• -D, --debug-file=[debugfile] — Write debug information to given file
• -V, --version — Display version information and exit
• -h, --help — Display help and exit
• --plug-separator=[char] — Separator for plug parameter when specifying more than 1 plug (Default Value: ,)
• --delay=[seconds] — Wait X seconds before fencing is started (Default Value: 0)
• --disable-timeout=[true/false] — Disable timeout (true/false) (default: true when run from Pacemaker 2.0+)
• --login-timeout=[seconds] — Wait X seconds for cmd prompt after login (Default Value: 5)
• --mpathpersist-path=[path] — Path to mpathpersist binary (Default Value: /usr/sbin/mpathpersist)
• --power-timeout=[seconds] — Test X seconds for status change after ON/OFF (Default Value: 20)
• --power-wait=[seconds] — Wait X seconds after issuing ON/OFF (Default Value: 0)
• --shell-timeout=[seconds] — Wait X seconds for cmd prompt after issuing command (Default Value: 3)
• --stonith-status-sleep=[seconds] — Sleep X seconds between status calls during a STONITH action (Default Value: 1)
• --store-path=[path] — Path to directory where fence agent can store information (Default Value: /var/run/cluster)
• --retry-on=[attempts] — Count of attempts to retry power on (Default Value: 1)
• --use-sudo — Use sudo (without password) when calling 3rd party software
• --sudo-path=[path] — Path to sudo binary (Default Value: /usr/bin/sudo)

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👑 ACTIONS 👑

• on — Power on machine.
• off — Power off machine.
• status — This returns the status of the plug/virtual machine.
• monitor — Check the health of fence device
• metadata — Display the XML metadata describing this resource.
• manpage — The operational behavior of this is not known.
• validate-all — Validate if all required parameters are entered.

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🧚 STDIN PARAMETERS 🧚

• action — Fencing action (Default Value: off)
• devices — List of devices to use for current operation. Devices can be comma or space separated list of device-mapper multipath devices (eg. /dev/mapper/3600508b400105df70000e00000ac0000 or /dev/mapper/mpath1). Each device must support SCSI-3 persistent reservations.
• key — Replaced by port/-n/--plug
• plug — Key to use for the current operation. This key should be unique to a node and have to be written in /etc/multipath.conf. For the "on" action, the key specifies the key use to register the local node. For the "off" action, this key specifies the key to be removed from the device(s). Obsoletes: port
• suppress_errors — Error log suppression. Obsoletes: suppress-errors
• quiet — Disable logging to stderr. Does not affect --verbose or --debug-file or logging to syslog.
• verbose — Verbose mode. Multiple -v flags can be stacked on the command line (e.g., -vvv) to increase verbosity.
• verbose_level — Level of debugging detail in output. Defaults to the number of --verbose flags specified on the command line, or to 1 if verbose=1 in a stonith device configuration (i.e., on stdin).
• debug_file — Write debug information to given file Obsoletes: debug
• version — Display version information and exit
• help — Display help and exit
• plug_separator — Separator for plug parameter when specifying more than 1 plug (Default Value: ,)
• delay — Wait X seconds before fencing is started (Default Value: 0)
• disable_timeout — Disable timeout (true/false) (default: true when run from Pacemaker 2.0+)
• login_timeout — Wait X seconds for cmd prompt after login (Default Value: 5)
• mpathpersist_path — Path to mpathpersist binary (Default Value: /usr/sbin/mpathpersist)
• power_timeout — Test X seconds for status change after ON/OFF (Default Value: 20)
• power_wait — Wait X seconds after issuing ON/OFF (Default Value: 0)
• shell_timeout — Wait X seconds for cmd prompt after issuing command (Default Value: 3)
• stonith_status_sleep — Sleep X seconds between status calls during a STONITH action (Default Value: 1)
• store_path — Path to directory where fence agent can store information (Default Value: /var/run/cluster)
• retry_on — Count of attempts to retry power on (Default Value: 1)
• use_sudo — Use sudo (without password) when calling 3rd party software Obsoletes: sudo
• sudo_path — Path to sudo binary (Default Value: /usr/bin/sudo)

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and that's the whole thing, bestie!! every flag, every default, every obsolete alias, all of it, we did NOT skip a single crumb 🍓

this lil masterpiece is fence_mpath (Fence Agent), dated 2009-10-20, and it belongs to the FENCE_AGENT(8) manual 💜 go forth and fence responsibly, mwah 💅✨