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)