NAME

       dmeventd — Device-mapper event daemon

SYNOPSIS

       dmeventd [-d [-d [-d]]] [-e exit_on_path] [-f] [-h] [-i] [-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.

       -e exit_on_path
              Specifies the file path whose presence is checked by the daemon when it receives a signal (SIGINT,
              SIGTERM)  and allows to exit even if there are still monitored devices.  This can help with system
              shutdown where devices have not been unmonitored properly.  To disable this behavior set  this  to
              the empty string "".  Default value is "/run/nologin".

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

       -h     Show help information.

       -i     Query  the running daemon instance for the status information. The format is internal and unstable
              and it is targeted for developers.  Format may change between versions.

       -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 than 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 command fails, dmeventd thin plugin  will  keep
              retrying  execution  with  increasing  time delay between retries up to 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  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 than 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  command  fails, dmeventd vdo plugin will keep
              retrying execution with increasing time delay between retries up to 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 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 executed 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 executed 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 interaction with dmeventd by any
              executed lvm2 command from a thin_command, vdo_command environment.

SEE ALSO

       lvm(8), lvm.conf(5), lvextend(8),
       fstrim(8)

Red Hat Inc                             DM TOOLS 2.03.31(2) (2025-02-27)                             DMEVENTD(8)