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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | LVM PLUGINS | ENVIRONMENT VARIABLES | SEE ALSO | COLOPHON |
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DMEVENTD(8) System Manager's Manual DMEVENTD(8)
dmeventd — Device-mapper event daemon
dmeventd [-d [-d [-d]]] [-f] [-h] [-l] [-R] [-V] [-?]
dmeventd is the event monitoring daemon for device-mapper devices.
Library plugins can register and carry out actions triggered when
particular events occur.
-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.
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).
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.
lvm(8), lvm.conf(5), lvextend(8),
fstrim(8)
This page is part of the lvm2 (Logical Volume Manager 2) project.
Information about the project can be found at
⟨http://www.sourceware.org/lvm2/⟩. If you have a bug report for
this manual page, see ⟨https://github.com/lvmteam/lvm2/issues⟩.
This page was obtained from the project's upstream Git repository
⟨git://sourceware.org/git/lvm2.git⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-08.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Red Hat Inc DM TOOLS 2.03.15(2)-git (2021-10-20) DMEVENTD(8)
Pages that refer to this page: lvmraid(7), lvmthin(7), lvchange(8), lvconvert(8), lvcreate(8), lvdisplay(8), lvextend(8), lvm(8), lvmconfig(8), lvmdevices(8), lvmdiskscan(8), lvm-fullreport(8), lvm-lvpoll(8), lvreduce(8), lvremove(8), lvrename(8), lvresize(8), lvs(8), lvscan(8), pvchange(8), pvck(8), pvcreate(8), pvdisplay(8), pvmove(8), pvremove(8), pvresize(8), pvs(8), pvscan(8), vgcfgbackup(8), vgcfgrestore(8), vgchange(8), vgck(8), vgconvert(8), vgcreate(8), vgdisplay(8), vgexport(8), vgextend(8), vgimport(8), vgimportclone(8), vgimportdevices(8), vgmerge(8), vgmknodes(8), vgreduce(8), vgremove(8), vgrename(8), vgs(8), vgscan(8), vgsplit(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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