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ZED(8)			  BSD System Manager's Manual			ZED(8)

     ZED -- ZFS	Event Daemon

     ZED [-fFhILMvVZ] [-d zedletdir] [-p pidfile] [-P path] [-s	statefile]
	 [-j jobs]

     The ZED (ZFS Event	Daemon)	monitors events	generated by the ZFS kernel
     module.  When a zevent (ZFS Event)	is posted, the ZED will	run any
     ZEDLETs (ZFS Event	Daemon Linkage for Executable Tasks) that have been
     enabled for the corresponding zevent class.

     -h	 Display a summary of the command-line options.

     -L	 Display license information.

     -V	 Display version information.

     -v	 Be verbose.

     -f	 Force the daemon to run if at all possible, disabling security	checks
	 and throwing caution to the wind.  Not	recommended for	use in produc-

     -F	 Don't daemonise: remain attached to the controlling terminal, log to
	 the standard I/O streams.

     -M	 Lock all current and future pages in the virtual memory address
	 space.	 This may help the daemon remain responsive when the system is
	 under heavy memory pressure.

     -I	 Request that the daemon idle rather than exit when the	kernel modules
	 are not loaded.  Processing of	events will start, or resume, when the
	 kernel	modules	are (re)loaded.	 Under Linux the kernel	modules	cannot
	 be unloaded while the daemon is running.

     -Z	 Zero the daemon's state, thereby allowing zevents still within	the
	 kernel	to be reprocessed.

     -d	zedletdir
	 Read the enabled ZEDLETs from the specified directory.

     -p	pidfile
	 Write the daemon's process ID to the specified	file.

     -P	path
	 Custom	$PATH for zedlets to use.  Normally zedlets run	in a locked-
	 down environment, with	hardcoded paths	to the ZFS commands ($ZFS,
	 $ZPOOL, $ZED, ...), and a hard-coded $PATH.  This is done for secu-
	 rity reasons.	However, the ZFS test suite uses a custom PATH for its
	 ZFS commands, and passes it to	ZED with -P.  In short,	-P is only to
	 be used by the	ZFS test suite;	never use it in	production!

     -s	statefile
	 Write the daemon's state to the specified file.

     -j	jobs
	 Allow at most jobs ZEDLETs to run concurrently, delaying execution of
	 new ones until	they finish.  Defaults to 16.

     A zevent is comprised of a	list of	nvpairs	(name/value pairs).  Each
     zevent contains an	EID (Event IDentifier) that uniquely identifies	it
     throughout	the lifetime of	the loaded ZFS kernel module; this EID is a
     monotonically increasing integer that resets to 1 each time the kernel
     module is loaded.	Each zevent also contains a class string that identi-
     fies the type of event.  For brevity, a subclass string is	defined	that
     omits the leading components of the class string.	Additional nvpairs ex-
     ist to provide event details.

     The kernel	maintains a list of recent zevents that	can be viewed (along
     with their	associated lists of nvpairs) using the zpool events -v com-

     ZEDLETs to	be invoked in response to zevents are located in the
     enabled-zedlets directory (zedletdir).  These can be symlinked or copied
     from the installed-zedlets	directory; symlinks allow for automatic	up-
     dates from	the installed ZEDLETs, whereas copies preserve local modifica-
     tions.  As	a security measure, since ownership change is a	privileged op-
     eration, ZEDLETs must be owned by root.  They must	have execute permis-
     sions for the user, but they must not have	write permissions for group or
     other.  Dotfiles are ignored.

     ZEDLETs are named after the zevent	class for which	they should be in-
     voked.  In	particular, a ZEDLET will be invoked for a given zevent	if ei-
     ther its class or subclass	string is a prefix of its filename (and	is
     followed by a non-alphabetic character).  As a special case, the prefix
     all matches all zevents.  Multiple	ZEDLETs	may be invoked for a given

     ZEDLETs are executables invoked by	the ZED	in response to a given zevent.
     They should be written under the presumption they can be invoked concur-
     rently, and they should use appropriate locking to	access any shared re-
     sources.  Common variables	used by	ZEDLETs	can be stored in the default
     rc	file which is sourced by scripts; these	variables should be prefixed
     with ZED_.

     The zevent	nvpairs	are passed to ZEDLETs as environment variables.	 Each
     nvpair name is converted to an environment	variable in the	following man-
     1.	  it is	prefixed with ZEVENT_,
     2.	  it is	converted to uppercase,	and
     3.	  each non-alphanumeric	character is converted to an underscore.

     Some additional environment variables have	been defined to	present	cer-
     tain nvpair values	in a more convenient form.  An incomplete list of
     zevent environment	variables is as	follows:
     ZEVENT_EID		 The Event IDentifier.
     ZEVENT_CLASS	 The zevent class string.
     ZEVENT_SUBCLASS	 The zevent subclass string.
     ZEVENT_TIME	 The time at which the zevent was posted as "seconds
			 nanoseconds" since the	Epoch.
     ZEVENT_TIME_SECS	 The seconds component of ZEVENT_TIME.
     ZEVENT_TIME_NSECS	 The nanoseconds component of ZEVENT_TIME.
     ZEVENT_TIME_STRING	 An almost-RFC3339-compliant string for	ZEVENT_TIME.

     Additionally, the following ZED & ZFS variables are defined:
     ZED_PID		 The daemon's process ID.
     ZED_ZEDLET_DIR	 The daemon's current enabled-zedlets directory.
     ZFS_ALIAS		 The alias ("name-version-release") string of the ZFS
			 distribution the daemon is part of.
     ZFS_VERSION	 The ZFS version the daemon is part of.
     ZFS_RELEASE	 The ZFS release the daemon is part of.

     ZEDLETs may need to call other ZFS	commands.  The installation paths of
     the following executables are defined as environment variables: ZDB, ZED,
     ZFS, ZINJECT, and ZPOOL.  These variables may be overridden in the	rc

	 The default directory for enabled ZEDLETs.

	 The default rc	file for common	variables used by ZEDLETs.

	 The default directory for installed ZEDLETs.

	 The default file containing the daemon's process ID.

	 The default file containing the daemon's state.

	 Reconfigure the daemon	and rescan the directory for enabled ZEDLETs.

	 Terminate the daemon.

     zfs(8), zpool(8), zpool-events(8)

     The ZED requires root privileges.

     Do	not taunt the ZED.

     ZEDLETs are unable	to return state/status information to the kernel.

     Internationalization support via gettext has not been added.

BSD				 May 26, 2021				   BSD


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