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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 reg‐
       ister 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
              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 re‐
              size  thin  pool  when  it's  been   filled   above   configured   threshold   activa‐
              tion/thin_pool_autoextend_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 command to support more advanced maintenance opera‐
              tions 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
              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 con‐
              figured  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 command
              fails, dmeventd vdo plugin will keep retrying execution with increasing time delay be‐
              tween  retries  upto  42 minutes.  User may also configure external command to support
              more advanced maintenance operations of a VDO pool.  Such external  command  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 program. Value present ac‐
              tual  usage  of  thin  pool  data volume. Variable is not set when error event is pro‐
              cessed.

       DMEVENTD_THIN_POOL_METADATA
              Variable is set by thin plugin and is available to executed program. Value present ac‐
              tual  usage of thin pool metadata volume. Variable is not set when error event is pro‐
              cessed.

       DMEVENTD_VDO_POOL
              Variable is set by vdo plugin and is available to executed program. Value present  ac‐
              tual 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)



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