NAME

       ZED - ZFS Event Daemon

SYNOPSIS

       zed [-d zedletdir] [-f] [-F] [-h] [-L] [-M] [-p pidfile] [-s statefile] [-v] [-V] [-Z]

DESCRIPTION

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

OPTIONS

       -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 production.

       -F     Run the daemon in the foreground.

       -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.

       -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.

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

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.

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

CONFIGURATION

       ZEDLETs to be invoked in response to zevents are located in the enabled-zedlets directory.  These can  be
       symlinked  or  copied from the installed-zedlets directory; symlinks allow for automatic updates from the
       installed ZEDLETs, whereas copies preserve local modifications.  As a security measure, 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.

       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 "all" matches all zevents.
       Multiple ZEDLETs may be invoked for a given zevent.

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 "ZED_".

       The zevent nvpairs are passed to ZEDLETs 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:

       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 ZFS alias (name-version-release) string used to build the daemon.

       ZFS_VERSION
              The ZFS version used to build the daemon.

       ZFS_RELEASE
              The ZFS release used to build the daemon.

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

FILES

       /etc/zfs/zed.d
              The default directory for enabled ZEDLETs.

       /etc/zfs/zed.d/zed.rc
              The default rc file for common variables used by ZEDLETs.

       /usr/lib/zfs-linux/zfs/zed.d
              The default directory for installed ZEDLETs.

       /var/run/zed.pid
              The default file containing the daemon's process ID.

       /var/run/zed.state
              The default file containing the daemon's state.

SIGNALS

       HUP    Reconfigure the daemon and rescan the directory for enabled ZEDLETs.

       TERM   Terminate the daemon.

NOTES

       ZED requires root privileges.

BUGS

       Events  are  processed  synchronously  by a single thread.  This can delay the processing of simultaneous
       zevents.

       There is no maximum timeout for ZEDLET execution.  Consequently,  a  misbehaving  ZEDLET  can  delay  the
       processing of subsequent zevents.

       The  ownership  and  permissions of the enabled-zedlets 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  ZEDLET to be executed as root.  The requirement that ZEDLETs be owned by root mitigates
       this to some extent.

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

       Some zevent nvpair types are not handled.  These are denoted by zevent  environment  variables  having  a
       "_NOT_IMPLEMENTED_" value.

       Internationalization support via gettext has not been added.

       The configuration file is not yet implemented.

       The diagnosis engine is not yet implemented.

LICENSE

       ZED  (ZFS Event Daemon) is distributed under the terms of the Common Development and Distribution License
       Version 1.0 (CDDL-1.0).

       Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).

SEE ALSO

       zfs(8), zpool(8)

ZFS on Linux                                    Octember 1, 2013                                          ZED(8)