zfs/man/man8/zed.8.in

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.\" Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
.\" Copyright (C) 2013-2014 Lawrence Livermore National Security, LLC.
.\"
.TH ZED 8 "Octember 1, 2013" "ZFS on Linux" "System Administration Commands"

.SH NAME
zed \- ZFS Event Daemon

.SH SYNOPSIS
.HP
.B zed
.\" [\fB\-c\fR \fIconfigfile\fR]
[\fB\-d\fR \fIscriptdir\fR]
[\fB\-f\fR]
[\fB\-F\fR]
[\fB\-h\fR]
[\fB\-L\fR]
[\fB\-M\fR]
[\fB\-p\fR \fIpidfile\fR]
[\fB\-s\fR \fIstatefile\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[\fB\-Z\fR]

.SH DESCRIPTION
.PP
\fBzed\fR (ZFS Event Daemon) monitors events generated by the ZFS kernel
module.  When a ZFS event (zevent) is posted, \fBzed\fR will run any scripts
that have been enabled for the corresponding zevent class.

.SH OPTIONS
.TP
.BI \-h
Display a summary of the command-line options.
.TP
.BI \-L
Display license information.
.TP
.BI \-V
Display version information.
.TP
.BI \-v
Be verbose.
.TP
.BI \-f
Force the daemon to run if at all possible, disabling security checks and
throwing caution to the wind.  Not recommended for use in production.
.TP
.BI \-F
Run the daemon in the foreground.
.TP
.BI \-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.
.TP
.BI \-Z
Zero the daemon's state, thereby allowing zevents still within the kernel
to be reprocessed.
.\" .TP
.\" .BI \-c\  configfile
.\" Read the configuration from the specified file.
.TP
.BI \-d\  scriptdir
Read the enabled scripts from the specified directory.
.TP
.BI \-p\  pidfile
Write the daemon's process ID to the specified file.
.TP
.BI \-s\  statefile
Write the daemon's state to the specified file.

.SH ZEVENTS
.PP
A zevent is comprised of a list of name/value pairs (nvpairs).  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 identifies the type of event.
For brevity, a subclass string is defined that omits the leading components
of the class string.  Additional nvpairs exist to provide event details.
.PP
The kernel maintains a list of recent zevents that can be viewed (along with
their associated lists of nvpairs) using the "\fBzpool events \-v\fR" command.

.SH CONFIGURATION
.PP
The scripts to be invoked in response to zevents are located in the
enabled-scripts directory.  These can be symlinked or copied from the
installed-scripts directory; symlinks allow for automatic updates from the
installed scripts, whereas copies preserve local modifications.  As a security
measure, scripts must be owned by root.  They must have execute permissions
for the user, but they must not have write permissions for group or other.
Dotfiles are ignored.
.PP
Scripts are named after the zevent class for which they should be invoked.
In particular, a script will be invoked for a given zevent if either 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 scripts may be invoked for a given zevent.

.SH SCRIPTS
.PP
Scripts should be written under the presumption they can be invoked
concurrently, and they should use appropriate locking to access any shared
resources.  Common variables used by the scripts can be stored in the default
rc file which is sourced by the scripts; these variables should be prefixed
with "ZED_".
.PP
The zevent nvpairs are passed to the scripts as environment variables.
Each nvpair name is converted to an environment variable in the following
manner: 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 certain
nvpair values in a more convenient form.  An incomplete list of zevent
environment variables is as follows:
.TP
.B
ZEVENT_EID
The Event IDentifier.
.TP
.B
ZEVENT_CLASS
The zevent class string.
.TP
.B
ZEVENT_SUBCLASS
The zevent subclass string.
.TP
.B
ZEVENT_TIME
The time at which the zevent was posted as
"\fIseconds\fR\ \fInanoseconds\fR" since the Epoch.
.TP
.B
ZEVENT_TIME_SECS
The \fIseconds\fR component of ZEVENT_TIME.
.TP
.B
ZEVENT_TIME_NSECS
The \fInanoseconds\fR component of ZEVENT_TIME.
.TP
.B
ZEVENT_TIME_STRING
An almost-RFC3339-compliant string for ZEVENT_TIME.
.PP
Additionally, the following ZED & ZFS variables are defined:
.TP
.B
ZED_PID
The daemon's process ID.
.TP
.B
ZED_SCRIPT_DIR
The daemon's current enabled-scripts directory.
.TP
.B
ZFS_ALIAS
The ZFS alias (name-ver-rel) string used to build the daemon.
.TP
.B
ZFS_VERSION
The ZFS version used to build the daemon.
.TP
.B
ZFS_RELEASE
The ZFS release used to build the daemon.
.PP
Scripts may need to call other ZFS commands.  The installation paths of
the following executables are defined: \fBZDB\fR, \fBZED\fR, \fBZFS\fR,
\fBZINJECT\fR, and \fBZPOOL\fR.  These variables can be overridden in the
zed.rc if needed.

.SH FILES
.\" .TP
.\" @sysconfdir@/zfs/zed.conf
.\" The default configuration file for the daemon.
.TP
.I @sysconfdir@/zfs/zed.d
The default directory for enabled scripts.
.TP
.I @sysconfdir@/zfs/zed.d/zed.rc
The default rc file for common variables used by the scripts.
.TP
.I @libexecdir@/zfs/zed.d
The default directory for installed scripts.
.TP
.I @runstatedir@/zed.pid
The default file containing the daemon's process ID.
.TP
.I @runstatedir@/zed.state
The default file containing the daemon's state.

.SH SIGNALS
.TP
.B HUP
Reconfigure the daemon and rescan the directory for enabled scripts.
.TP
.B TERM
Terminate the daemon.

.SH NOTES
.PP
\fBzed\fR requires root privileges.
.\" Do not taunt zed.

.SH BUGS
.PP
Events are processed synchronously by a single thread.  This can delay the
processing of simultaneous zevents.
.PP
There is no maximum timeout for script execution.  Consequently, a misbehaving
script can delay the processing of subsequent zevents.
.PP
The ownership and permissions of the enabled-scripts directory (along
with all parent directories) are not checked.  If any of these directories
are improperly owned or permissioned, an unprivileged user could insert a
script to be executed as root.  The requirement that scripts be owned by
root mitigates this to some extent.
.PP
Scripts are unable to return state/status information to the kernel.
.PP
Some zevent nvpair types are not handled.  These are denoted by zevent
environment variables having a "_NOT_IMPLEMENTED_" value.
.PP
Internationalization support via gettext has not been added.
.PP
The configuration file is not yet implemented.
.PP
The diagnosis engine is not yet implemented.

.SH COPYRIGHT
.PP
Developed at Lawrence Livermore National Laboratory (LLNL\-CODE\-403049).
.br
Copyright (C) 2013\-2014 Lawrence Livermore National Security, LLC.

.SH LICENSE
.PP
\fBzed\fR (ZFS Event Daemon) is distributed under the terms of the
Common Development and Distribution License (CDDL\-1.0).

.SH SEE ALSO
.BR zfs (8),
.BR zpool (8)