Provided by: dmeventd_1.02.201-1ubuntu1_amd64 
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 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)