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  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 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 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)