DMEVENTD(8)    (DM TOOLS 2.03.11(2) (2021-01-08))     DMEVENTD(8)

     NAME
          dmeventd - Device-mapper event daemon

     SYNOPSIS
          dmeventd [-d [-d [-d]]] [-f] [-h] [-l] [-R] [-V] [-?]

     DESCRIPTION
          dmeventd is the event monitoring daemon for device-mapper
          devices.  Library plugins can register and carry out actions
          triggered when particular events occur.

     OPTIONS
          -d
               Repeat from 1 to 3 times ( -d, -dd, -ddd ) to increase
               the detail of debug messages sent to syslog.  Each
               extra d adds more debugging information.

          -f
               Don't fork, run in the foreground.

          -h
               Show help information.

          -l
               Log through stdout and stderr instead of syslog.  This
               option works only with option -f, otherwise it is
               ignored.

          -?
               Show help information on stderr.

          -R
               Replace a running dmeventd instance. The running
               dmeventd must be version 2.02.77 or newer. The new
               dmeventd instance will obtain a list of devices and
               events to monitor from the currently running daemon.

          -V
               Show version of dmeventd.

     LVM PLUGINS
          Mirror
               Attempts to handle device failure automatically. See
               lvm.conf(5).

          Raid
               Attempts to handle device failure automatically. See
               lvm.conf(5).

          Snapshot

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               Monitors how full a snapshot is becoming and emits a
               warning to syslog when it exceeds 80% full.  The warn-
               ing is repeated when 85%, 90% and 95% of the snapshot
               is filled.  See lvm.conf(5).  Snapshot which runs out
               of space gets invalid and when it is mounted, it gets
               umounted if possible.

          Thin
               Monitors how full a thin pool data and metadata is
               becoming and emits a warning to syslog when it exceeds
               80% full.  The warning is repeated when more then 85%,
               90% and 95% of the thin pool is filled. See
               lvm.conf(5).  When a thin pool fills over 50% (data or
               metadata) thin plugin calls configured
               dmeventd/thin_command with every 5% increase.  With
               default setting it calls internal lvm lvextend
               --use-policies to resize thin pool when it's been
               filled above configured threshold
               activation/thin_pool_autoextend_threshold.  If the com-
               mand fails, dmeventd thin plugin will keep retrying
               execution with increasing time delay between retries
               upto 42 minutes.  User may also configure external com-
               mand to support more advanced maintenance operations of
               a thin pool.  Such external command can e.g. remove
               some unneeded snapshots, use fstrim(8) to free recover
               space in a thin pool, but also can use lvextend
               --use-policies if other actions have not released
               enough space.  Command is executed with environmental
               variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 command exe-
               cuted in this environment will not try to interact with
               dmeventd.  To see the fullness of a thin pool command
               may check these two environmental variables
               DMEVENTD_THIN_POOL_DATA and
               DMEVENTD_THIN_POOL_METADATA.  Command can also read
               status with tools like lvs(8).

          Vdo
               Monitors how full a VDO pool data is becoming and emits
               a warning to syslog when it exceeds 80% full.  The
               warning is repeated when more then 85%, 90% and 95% of
               the VDO pool is filled. See lvm.conf(5).  When a VDO
               pool fills over 50% vdo plugin calls configured
               dmeventd/vdo_command with every 5% increase.  With
               default setting it calls internal lvm lvextend
               --use-policies to resize VDO pool when it's been filled
               above the configured threshold
               activation/vdo_pool_autoextend_threshold.  If the com-
               mand fails, dmeventd vdo plugin will keep retrying exe-
               cution with increasing time delay between retries upto
               42 minutes.  User may also configure external command
               to support more advanced maintenance operations of a

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               VDO pool.  Such external command can e.g. remove some
               unneeded space with fstrim(8), but also can use lvex-
               tend --use-policies if other actions have not released
               enough space.  Command is executed with environmental
               variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 command exe-
               cuted in this environment will not try to interact with
               dmeventd.  To see the fullness of a VDO pool command
               may check this environmental variable
               DMEVENTD_VDO_POOL.  Command can also read status with
               tools like lvs(8).

     ENVIRONMENT VARIABLES
          DMEVENTD_THIN_POOL_DATA
               Variable is set by thin plugin and is available to exe-
               cuted program. Value present actual usage of thin pool
               data volume. Variable is not set when error event is
               processed.

          DMEVENTD_THIN_POOL_METADATA
               Variable is set by thin plugin and is available to exe-
               cuted program. Value present actual usage of thin pool
               metadata volume. Variable is not set when error event
               is processed.

          DMEVENTD_VDO_POOL
               Variable is set by vdo plugin and is available to exe-
               cuted program. Value present actual usage of VDO pool
               data volume. Variable is not set when error event is
               processed.

          LVM_RUN_BY_DMEVENTD
               Variable is set by thin and vdo plugin to prohibit
               recursive interation with dmeventd by any executed lvm2
               command from a thin_command, vdo_command environment.

     SEE ALSO
          lvm(8), lvm.conf(5)

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