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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.  Li-
       brary plugins can register and carry out actions triggered when partic-
       ular events occur.

OPTIONS
       -d
              Repeat  from  1 to 3 times ( -d, -dd, -ddd ) to increase the de-
              tail 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 ob-
              tain 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
              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  re-
              tries upto 42 minutes.  User may also configure external command
              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 executed in this envi-
              ronment will not try to interact  with  dmeventd.   To  see  the
              fullness  of a thin pool command may check these two environmen-
              tal        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  warn-
              ing 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  execution
              with  increasing  time  delay  between  retries upto 42 minutes.
              User may also configure external command  to  support  more  ad-
              vanced maintenance operations of a VDO pool.  Such external com-
              mand can e.g. remove some unneeded  space  with  fstrim(8),  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 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 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.

       DMEVENTD_VDO_POOL
              Variable  is set by vdo plugin and is available to executed pro-
              gram. Value present actual usage of VDO pool data volume.  Vari-
              able is not set when error event is processed.

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

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

Red Hat Inc            DM TOOLS 2.03.07(2) (2019-11-30)            DMEVENTD(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | LVM PLUGINS | ENVIRONMENT VARIABLES | SEE ALSO