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Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz> Closes #12125
257 lines
7.4 KiB
Groff
257 lines
7.4 KiB
Groff
.\"
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.\" This file is part of the ZFS Event Daemon (ZED).
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.\" Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
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.\" Copyright (C) 2013-2014 Lawrence Livermore National Security, LLC.
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.\" Refer to the OpenZFS git commit log for authoritative copyright attribution.
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.\"
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.\" The contents of this file are subject to the terms of the
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.\" Common Development and Distribution License Version 1.0 (CDDL-1.0).
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.\" You can obtain a copy of the license from the top-level file
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.\" "OPENSOLARIS.LICENSE" or at <http://opensource.org/licenses/CDDL-1.0>.
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.\" You may not use this file except in compliance with the license.
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.\"
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.\" Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049)
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.\"
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.Dd May 26, 2021
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.Dt ZED 8
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.Os
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.
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.Sh NAME
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.Nm ZED
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.Nd ZFS Event Daemon
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.Sh SYNOPSIS
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.Nm
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.Op Fl fFhILMvVZ
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.Op Fl d Ar zedletdir
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.Op Fl p Ar pidfile
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.Op Fl P Ar path
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.Op Fl s Ar statefile
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.Op Fl j Ar jobs
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.
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.Sh DESCRIPTION
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The
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.Nm
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(ZFS Event Daemon) monitors events generated by the ZFS kernel
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module.
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When a zevent (ZFS Event) is posted, the
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.Nm
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will run any ZEDLETs (ZFS Event Daemon Linkage for Executable Tasks)
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that have been enabled for the corresponding zevent class.
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.
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.Sh OPTIONS
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.Bl -tag -width "-h"
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.It Fl h
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Display a summary of the command-line options.
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.It Fl L
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Display license information.
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.It Fl V
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Display version information.
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.It Fl v
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Be verbose.
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.It Fl f
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Force the daemon to run if at all possible, disabling security checks and
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throwing caution to the wind.
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Not recommended for use in production.
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.It Fl F
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Don't daemonise: remain attached to the controlling terminal,
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log to the standard I/O streams.
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.It Fl M
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Lock all current and future pages in the virtual memory address space.
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This may help the daemon remain responsive when the system is under heavy
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memory pressure.
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.It Fl I
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Request that the daemon idle rather than exit when the kernel modules are not loaded.
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Processing of events will start, or resume, when the kernel modules are (re)loaded.
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Under Linux the kernel modules cannot be unloaded while the daemon is running.
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.It Fl Z
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Zero the daemon's state, thereby allowing zevents still within the kernel
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to be reprocessed.
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.It Fl d Ar zedletdir
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Read the enabled ZEDLETs from the specified directory.
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.It Fl p Ar pidfile
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Write the daemon's process ID to the specified file.
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.It Fl P Ar path
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Custom
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.Ev $PATH
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for zedlets to use.
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Normally zedlets run in a locked-down environment, with hardcoded paths to the ZFS commands
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.Pq Ev $ZFS , $ZPOOL , $ZED , ... ,
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and a hard-coded
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.Ev $PATH .
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This is done for security reasons.
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However, the ZFS test suite uses a custom PATH for its ZFS commands, and passes it to
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.Nm
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with
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.Fl P .
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In short,
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.Fl P
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is only to be used by the ZFS test suite; never use
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it in production!
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.It Fl s Ar statefile
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Write the daemon's state to the specified file.
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.It Fl j Ar jobs
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Allow at most
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.Ar jobs
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ZEDLETs to run concurrently,
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delaying execution of new ones until they finish.
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Defaults to
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.Sy 16 .
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.El
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.Sh ZEVENTS
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A zevent is comprised of a list of nvpairs (name/value pairs).
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Each zevent contains an EID (Event IDentifier) that uniquely identifies it throughout
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the lifetime of the loaded ZFS kernel module; this EID is a monotonically
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increasing integer that resets to 1 each time the kernel module is loaded.
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Each zevent also contains a class string that identifies the type of event.
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For brevity, a subclass string is defined that omits the leading components
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of the class string.
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Additional nvpairs exist to provide event details.
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.Pp
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The kernel maintains a list of recent zevents that can be viewed (along with
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their associated lists of nvpairs) using the
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.Nm zpool Cm events Fl v
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command.
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.
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.Sh CONFIGURATION
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ZEDLETs to be invoked in response to zevents are located in the
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.Em enabled-zedlets
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directory
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.Pq Ar zedletdir .
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These can be symlinked or copied from the
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.Em installed-zedlets
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directory; symlinks allow for automatic updates
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from the installed ZEDLETs, whereas copies preserve local modifications.
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As a security measure, since ownership change is a privileged operation,
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ZEDLETs must be owned by root.
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They must have execute permissions for the user,
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but they must not have write permissions for group or other.
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Dotfiles are ignored.
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.Pp
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ZEDLETs are named after the zevent class for which they should be invoked.
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In particular, a ZEDLET will be invoked for a given zevent if either its
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class or subclass string is a prefix of its filename (and is followed by
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a non-alphabetic character).
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As a special case, the prefix
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.Sy all
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matches all zevents.
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Multiple ZEDLETs may be invoked for a given zevent.
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.
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.Sh ZEDLETS
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ZEDLETs are executables invoked by the ZED in response to a given zevent.
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They should be written under the presumption they can be invoked concurrently,
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and they should use appropriate locking to access any shared resources.
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Common variables used by ZEDLETs can be stored in the default rc file which
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is sourced by scripts; these variables should be prefixed with
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.Sy ZED_ .
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.Pp
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The zevent nvpairs are passed to ZEDLETs as environment variables.
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Each nvpair name is converted to an environment variable in the following
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manner:
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.Bl -enum
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.It
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it is prefixed with
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.Sy ZEVENT_ ,
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.It
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it is converted to uppercase, and
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.It
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each non-alphanumeric character is converted to an underscore.
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.El
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.Pp
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Some additional environment variables have been defined to present certain
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nvpair values in a more convenient form.
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An incomplete list of zevent environment variables is as follows:
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.Bl -tag -width "ZEVENT_TIME_STRING"
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.It Sy ZEVENT_EID
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The Event IDentifier.
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.It Sy ZEVENT_CLASS
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The zevent class string.
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.It Sy ZEVENT_SUBCLASS
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The zevent subclass string.
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.It Sy ZEVENT_TIME
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The time at which the zevent was posted as
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.Dq Em seconds nanoseconds
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since the Epoch.
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.It Sy ZEVENT_TIME_SECS
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The
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.Em seconds
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component of
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.Sy ZEVENT_TIME .
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.It Sy ZEVENT_TIME_NSECS
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The
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.Em nanoseconds
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component of
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.Sy ZEVENT_TIME .
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.It Sy ZEVENT_TIME_STRING
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An almost-RFC3339-compliant string for
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.Sy ZEVENT_TIME .
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.El
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.Pp
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Additionally, the following ZED & ZFS variables are defined:
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.Bl -tag -width "ZEVENT_TIME_STRING"
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.It Sy ZED_PID
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The daemon's process ID.
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.It Sy ZED_ZEDLET_DIR
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The daemon's current
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.Em enabled-zedlets
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directory.
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.It Sy ZFS_ALIAS
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The alias
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.Pq Dq Em name Ns - Ns Em version Ns - Ns Em release
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string of the ZFS distribution the daemon is part of.
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.It Sy ZFS_VERSION
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The ZFS version the daemon is part of.
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.It Sy ZFS_RELEASE
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The ZFS release the daemon is part of.
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.El
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.Pp
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ZEDLETs may need to call other ZFS commands.
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The installation paths of the following executables are defined as environment variables:
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.Sy ZDB ,
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.Sy ZED ,
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.Sy ZFS ,
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.Sy ZINJECT ,
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and
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.Sy ZPOOL .
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These variables may be overridden in the rc file.
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.
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.Sh FILES
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.Bl -tag -width "-c"
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.It Pa @sysconfdir@/zfs/zed.d
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The default directory for enabled ZEDLETs.
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.It Pa @sysconfdir@/zfs/zed.d/zed.rc
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The default rc file for common variables used by ZEDLETs.
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.It Pa @zfsexecdir@/zed.d
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The default directory for installed ZEDLETs.
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.It Pa @runstatedir@/zed.pid
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The default file containing the daemon's process ID.
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.It Pa @runstatedir@/zed.state
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The default file containing the daemon's state.
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.El
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.
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.Sh SIGNALS
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.Bl -tag -width "-c"
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.It Sy SIGHUP
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Reconfigure the daemon and rescan the directory for enabled ZEDLETs.
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.It Sy SIGTERM , SIGINT
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Terminate the daemon.
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.El
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.
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.Sh SEE ALSO
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.Xr zfs-events 5 ,
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.Xr zfs 8 ,
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.Xr zpool 8 ,
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.Xr zpool-events 8
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.
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.Sh NOTES
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The
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.Nm
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requires root privileges.
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.Pp
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Do not taunt the
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.Nm .
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.
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.Sh BUGS
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ZEDLETs are unable to return state/status information to the kernel.
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.Pp
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Internationalization support via gettext has not been added.
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