dmeventd(8) - phpMan

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
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 op-
tion -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 ex-
ceeds 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 ev-
ery 5% increase. With default setting it calls internal lvm lvextend --use-poli-
cies to resize 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 mainte-
nance operations of a thin pool. Such external command can e.g. remove some un-
needed 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. Com-
mand is executed with environmental variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 com-
mand 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 com-
mand 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 lvex-
tend --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 exe-
cuted in this environment will not try to interact with dmeventd. To see the full-
ness 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 pro-
cessed.

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 pro-
cessed.

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.