FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/man/man8/zed.8.in

     .\"
     .\" This file is part of the ZFS Event Daemon (ZED).
     .\" Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
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     .\" Common Development and Distribution License Version 1.0 (CDDL-1.0).
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    .\" "OPENSOLARIS.LICENSE" or at <http://opensource.org/licenses/CDDL-1.0>.
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    .\" Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049)
    .\"
    .Dd May 26, 2021
    .Dt ZED 8
    .Os
    .
    .Sh NAME
    .Nm ZED
    .Nd ZFS Event Daemon
    .Sh SYNOPSIS
    .Nm
    .Op Fl fFhILMvVZ
    .Op Fl d Ar zedletdir
    .Op Fl p Ar pidfile
    .Op Fl P Ar path
    .Op Fl s Ar statefile
    .Op Fl j Ar jobs
    .Op Fl b Ar buflen
    .
    .Sh DESCRIPTION
    The
    .Nm
    (ZFS Event Daemon) monitors events generated by the ZFS kernel
    module.
    When a zevent (ZFS Event) is posted, the
    .Nm
    will run any ZEDLETs (ZFS Event Daemon Linkage for Executable Tasks)
    that have been enabled for the corresponding zevent class.
    .
    .Sh OPTIONS
    .Bl -tag -width "-h"
    .It Fl h
    Display a summary of the command-line options.
    .It Fl L
    Display license information.
    .It Fl V
    Display version information.
    .It Fl v
    Be verbose.
    .It Fl 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.
    .It Fl F
    Don't daemonise: remain attached to the controlling terminal,
    log to the standard I/O streams.
    .It Fl 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.
    .It Fl 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.
    .It Fl Z
    Zero the daemon's state, thereby allowing zevents still within the kernel
    to be reprocessed.
    .It Fl d Ar zedletdir
    Read the enabled ZEDLETs from the specified directory.
    .It Fl p Ar pidfile
    Write the daemon's process ID to the specified file.
    .It Fl P Ar path
    Custom
    .Ev $PATH
    for zedlets to use.
    Normally zedlets run in a locked-down environment, with hardcoded paths to the
    ZFS commands
    .Pq Ev $ZFS , $ZPOOL , $ZED , … ,
    and a hard-coded
    .Ev $PATH .
    This is done for security reasons.
    However, the ZFS test suite uses a custom PATH for its ZFS commands, and passes
    it to
    .Nm
    with
    .Fl P .
    In short,
    .Fl P
    is only to be used by the ZFS test suite; never use
    it in production!
    .It Fl s Ar statefile
    Write the daemon's state to the specified file.
    .It Fl j Ar jobs
    Allow at most
    .Ar jobs
   ZEDLETs to run concurrently,
   delaying execution of new ones until they finish.
   Defaults to
   .Sy 16 .
   .It Fl b Ar buflen
   Cap kernel event buffer growth to
   .Ar buflen
   entries.
   This buffer is grown when the daemon misses an event, but results in
   unreclaimable memory use in the kernel.
   A value of
   .Sy 0
   removes the cap.
   Defaults to
   .Sy 1048576 .
   .El
   .Sh ZEVENTS
   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 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
   .Nm zpool Cm events Fl v
   command.
   .
   .Sh CONFIGURATION
   ZEDLETs to be invoked in response to zevents are located in the
   .Em enabled-zedlets
   directory
   .Pq Ar zedletdir .
   These can be symlinked or copied from the
   .Em installed-zedlets
   directory; symlinks allow for automatic updates
   from the installed ZEDLETs, whereas copies preserve local modifications.
   As a security measure, since ownership change is a privileged operation,
   ZEDLETs 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
   ZEDLETs are named after the zevent class for which they should be invoked.
   In particular, a ZEDLET 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
   .Sy all
   matches all zevents.
   Multiple ZEDLETs may be invoked for a given zevent.
   .
   .Sh ZEDLETS
   ZEDLETs are executables invoked by the ZED in response to a given zevent.
   They 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 ZEDLETs can be stored in the default rc file which
   is sourced by scripts; these variables should be prefixed with
   .Sy ZED_ .
   .Pp
   The zevent nvpairs are passed to ZEDLETs as environment variables.
   Each nvpair name is converted to an environment variable in the following
   manner:
   .Bl -enum -compact
   .It
   it is prefixed with
   .Sy ZEVENT_ ,
   .It
   it is converted to uppercase, and
   .It
   each non-alphanumeric character is converted to an underscore.
   .El
   .Pp
   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:
   .Bl -tag -compact -width "ZEVENT_TIME_STRING"
   .It Sy ZEVENT_EID
   The Event IDentifier.
   .It Sy ZEVENT_CLASS
   The zevent class string.
   .It Sy ZEVENT_SUBCLASS
   The zevent subclass string.
   .It Sy ZEVENT_TIME
   The time at which the zevent was posted as
   .Dq Em seconds nanoseconds
   since the Epoch.
   .It Sy ZEVENT_TIME_SECS
   The
   .Em seconds
   component of
   .Sy ZEVENT_TIME .
   .It Sy ZEVENT_TIME_NSECS
   The
   .Em nanoseconds
   component of
   .Sy ZEVENT_TIME .
   .It Sy ZEVENT_TIME_STRING
   An almost-RFC3339-compliant string for
   .Sy ZEVENT_TIME .
   .El
   .Pp
   Additionally, the following ZED & ZFS variables are defined:
   .Bl -tag -compact -width "ZEVENT_TIME_STRING"
   .It Sy ZED_PID
   The daemon's process ID.
   .It Sy ZED_ZEDLET_DIR
   The daemon's current
   .Em enabled-zedlets
   directory.
   .It Sy ZFS_ALIAS
   The alias
   .Pq Dq Em name Ns - Ns Em version Ns - Ns Em release
   string of the ZFS distribution the daemon is part of.
   .It Sy ZFS_VERSION
   The ZFS version the daemon is part of.
   .It Sy ZFS_RELEASE
   The ZFS release the daemon is part of.
   .El
   .Pp
   ZEDLETs may need to call other ZFS commands.
   The installation paths of the following executables are defined as environment
   variables:
   .Sy ZDB ,
   .Sy ZED ,
   .Sy ZFS ,
   .Sy ZINJECT ,
   and
   .Sy ZPOOL .
   These variables may be overridden in the rc file.
   .
   .Sh FILES
   .Bl -tag -width "-c"
   .It Pa @sysconfdir@/zfs/zed.d
   The default directory for enabled ZEDLETs.
   .It Pa @sysconfdir@/zfs/zed.d/zed.rc
   The default rc file for common variables used by ZEDLETs.
   .It Pa @zfsexecdir@/zed.d
   The default directory for installed ZEDLETs.
   .It Pa @runstatedir@/zed.pid
   The default file containing the daemon's process ID.
   .It Pa @runstatedir@/zed.state
   The default file containing the daemon's state.
   .El
   .
   .Sh SIGNALS
   .Bl -tag -width "-c"
   .It Sy SIGHUP
   Reconfigure the daemon and rescan the directory for enabled ZEDLETs.
   .It Sy SIGTERM , SIGINT
   Terminate the daemon.
   .El
   .
   .Sh SEE ALSO
   .Xr zfs 8 ,
   .Xr zpool 8 ,
   .Xr zpool-events 8
   .
   .Sh NOTES
   The
   .Nm
   requires root privileges.
   .Pp
   Do not taunt the
   .Nm .
   .
   .Sh BUGS
   ZEDLETs are unable to return state/status information to the kernel.
   .Pp
   Internationalization support via gettext has not been added.

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