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* Use all caps for document title. * Remove section name as it can be inferred from the section number. * Name "OpenZFS" as the document source. * Bump modification date. While here, fixed trailing whitespace reported by igor. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10792
269 lines
8.2 KiB
Groff
269 lines
8.2 KiB
Groff
.\"
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.\" This file is part of the ZFS Event Daemon (ZED)
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.\" for ZFS on Linux (ZoL) <https://zfsonlinux.org/>.
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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 ZoL 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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.TH ZED 8 "Aug 24, 2020" OpenZFS
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.SH NAME
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ZED \- ZFS Event Daemon
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.SH SYNOPSIS
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.HP
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.B zed
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.\" [\fB\-c\fR \fIconfigfile\fR]
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[\fB\-d\fR \fIzedletdir\fR]
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[\fB\-f\fR]
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[\fB\-F\fR]
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[\fB\-h\fR]
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[\fB\-I\fR]
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[\fB\-L\fR]
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[\fB\-M\fR]
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[\fB\-p\fR \fIpidfile\fR]
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[\fB\-P\fR \fIpath\fR]
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[\fB\-s\fR \fIstatefile\fR]
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[\fB\-v\fR]
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[\fB\-V\fR]
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[\fB\-Z\fR]
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.SH DESCRIPTION
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.PP
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\fBZED\fR (ZFS Event Daemon) monitors events generated by the ZFS kernel
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module. When a zevent (ZFS Event) is posted, \fBZED\fR will run any ZEDLETs
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(ZFS Event Daemon Linkage for Executable Tasks) that have been enabled for the
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corresponding zevent class.
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.SH OPTIONS
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.TP
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.BI \-h
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Display a summary of the command-line options.
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.TP
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.BI \-L
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Display license information.
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.TP
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.BI \-V
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Display version information.
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.TP
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.BI \-v
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Be verbose.
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.TP
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.BI \-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. Not recommended for use in production.
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.TP
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.BI \-F
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Run the daemon in the foreground.
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.TP
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.BI \-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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.TP
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.BI \-I
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Request that the daemon idle rather than exit when the kernel modules are
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not loaded. Processing of events will start, or resume, when the kernel
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modules are (re)loaded. Under Linux the kernel modules cannot be unloaded
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while the daemon is running.
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.TP
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.BI \-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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.\" .TP
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.\" .BI \-c\ configfile
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.\" Read the configuration from the specified file.
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.TP
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.BI \-d\ zedletdir
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Read the enabled ZEDLETs from the specified directory.
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.TP
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.BI \-p\ pidfile
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Write the daemon's process ID to the specified file.
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.TP
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.BI \-P\ path
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Custom $PATH for zedlets to use. Normally zedlets run in a locked-down
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environment, with hardcoded paths to the ZFS commands ($ZFS, $ZPOOL, $ZED, ...),
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and a hardcoded $PATH. This is done for security reasons. However, the
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ZFS test suite uses a custom PATH for its ZFS commands, and passes it to zed
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with -P. In short, -P is only to be used by the ZFS test suite; never use
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it in production!
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.TP
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.BI \-s\ statefile
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Write the daemon's state to the specified file.
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.SH ZEVENTS
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.PP
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A zevent is comprised of a list of nvpairs (name/value pairs). Each zevent
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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. 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 "\fBzpool events \-v\fR" command.
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.SH CONFIGURATION
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.PP
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ZEDLETs to be invoked in response to zevents are located in the
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\fIenabled-zedlets\fR directory. These can be symlinked or copied from the
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\fIinstalled-zedlets\fR 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, ZEDLETs must be owned by root. They must have
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execute permissions for the user, but they must not have write permissions
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for group or other. 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). As a special case, the prefix "all" matches
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all zevents. Multiple ZEDLETs may be invoked for a given zevent.
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.SH ZEDLETS
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.PP
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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 "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: 1) it is prefixed with "ZEVENT_", 2) it is converted to uppercase,
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and 3) each non-alphanumeric character is converted to an underscore.
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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. An incomplete list of zevent
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environment variables is as follows:
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.TP
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.B
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ZEVENT_EID
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The Event IDentifier.
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.TP
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.B
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ZEVENT_CLASS
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The zevent class string.
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.TP
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.B
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ZEVENT_SUBCLASS
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The zevent subclass string.
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.TP
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.B
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ZEVENT_TIME
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The time at which the zevent was posted as
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"\fIseconds\fR\ \fInanoseconds\fR" since the Epoch.
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.TP
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.B
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ZEVENT_TIME_SECS
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The \fIseconds\fR component of ZEVENT_TIME.
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.TP
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.B
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ZEVENT_TIME_NSECS
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The \fInanoseconds\fR component of ZEVENT_TIME.
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.TP
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.B
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ZEVENT_TIME_STRING
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An almost-RFC3339-compliant string for ZEVENT_TIME.
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.PP
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Additionally, the following ZED & ZFS variables are defined:
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.TP
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.B
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ZED_PID
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The daemon's process ID.
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.TP
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.B
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ZED_ZEDLET_DIR
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The daemon's current \fIenabled-zedlets\fR directory.
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.TP
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.B
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ZFS_ALIAS
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The ZFS alias (\fIname-version-release\fR) string used to build the daemon.
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.TP
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.B
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ZFS_VERSION
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The ZFS version used to build the daemon.
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.TP
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.B
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ZFS_RELEASE
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The ZFS release used to build the daemon.
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.PP
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ZEDLETs may need to call other ZFS commands. The installation paths of
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the following executables are defined: \fBZDB\fR, \fBZED\fR, \fBZFS\fR,
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\fBZINJECT\fR, and \fBZPOOL\fR. These variables can be overridden in the
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rc file if needed.
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.SH FILES
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.\" .TP
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.\" @sysconfdir@/zfs/zed.conf
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.\" The default configuration file for the daemon.
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.TP
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.I @sysconfdir@/zfs/zed.d
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The default directory for enabled ZEDLETs.
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.TP
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.I @sysconfdir@/zfs/zed.d/zed.rc
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The default rc file for common variables used by ZEDLETs.
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.TP
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.I @zfsexecdir@/zed.d
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The default directory for installed ZEDLETs.
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.TP
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.I @runstatedir@/zed.pid
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The default file containing the daemon's process ID.
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.TP
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.I @runstatedir@/zed.state
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The default file containing the daemon's state.
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.SH SIGNALS
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.TP
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.B HUP
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Reconfigure the daemon and rescan the directory for enabled ZEDLETs.
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.TP
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.B TERM
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Terminate the daemon.
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.SH NOTES
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.PP
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\fBZED\fR requires root privileges.
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.\" Do not taunt zed.
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.SH BUGS
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.PP
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Events are processed synchronously by a single thread. This can delay the
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processing of simultaneous zevents.
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.PP
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There is no maximum timeout for ZEDLET execution. Consequently, a misbehaving
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ZEDLET can delay the processing of subsequent zevents.
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.PP
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The ownership and permissions of the \fIenabled-zedlets\fR directory (along
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with all parent directories) are not checked. If any of these directories
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are improperly owned or permissioned, an unprivileged user could insert a
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ZEDLET to be executed as root. The requirement that ZEDLETs be owned by
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root mitigates this to some extent.
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.PP
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ZEDLETs are unable to return state/status information to the kernel.
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.PP
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Some zevent nvpair types are not handled. These are denoted by zevent
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environment variables having a "_NOT_IMPLEMENTED_" value.
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.PP
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Internationalization support via gettext has not been added.
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.PP
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The configuration file is not yet implemented.
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.PP
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The diagnosis engine is not yet implemented.
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.SH LICENSE
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.PP
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\fBZED\fR (ZFS Event Daemon) is distributed under the terms of the
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Common Development and Distribution License Version 1.0 (CDDL\-1.0).
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.PP
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Developed at Lawrence Livermore National Laboratory (LLNL\-CODE\-403049).
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.SH SEE ALSO
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.BR zfs (8),
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.BR zpool (8)
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.BR zpool-events (8)
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