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DMEVENTD(8)                 System Manager's Manual                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  par-
       ticular 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  cur-
              rently 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
              Monitors  how full a snapshot is becoming and emits a warning to
              syslog when it exceeds 80% full.  The warning 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_autoex-
              tend_threshold.  If the command 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 snap-
              shots, 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 executed in
              this environment will not try to interact with dmeventd.  To see
              the fullness of a thin pool command may check these two environ-
              mental       variables        DMEVENTD_THIN_POOL_DATA        and
              DMEVENTD_THIN_POOL_METADATA.   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 executed pro-
              gram. Value present actual usage of thin pool data volume. Vari-
              able is not set when error event is processed.
       DMEVENTD_THIN_POOL_METADATA
              Variable is set by thin plugin and is available to executed pro-
              gram.  Value  present actual usage of thin pool metadata volume.
              Variable is not set when error event is processed.
       LVM_RUN_BY_DMEVENTD
              Variable is set by thin plugin to prohibit recursive  interation
              with  dmeventd  by any executed lvm2 command from a thin_command
              environment.
SEE ALSO
       lvm(8), lvm.conf(5)

Red Hat Inc         DM TOOLS 2.02.187(2)-RHEL7 (2020-03-24)        DMEVENTD(8)