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
              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_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 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 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 command 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 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 interation 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 2.03.16(2) (2022-05-18)                             DMEVENTD(8)