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/x86_64-linux-gnu/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)