1DMEVENTD(8) System Manager's Manual DMEVENTD(8)
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6 dmeventd — Device-mapper event daemon
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9 dmeventd [-d [-d [-d]]] [-f] [-h] [-l] [-R] [-V] [-?]
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12 dmeventd is the event monitoring daemon for device-mapper devices.
13 Library plugins can register and carry out actions triggered when par‐
14 ticular events occur.
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17 -d
18 Repeat from 1 to 3 times ( -d, -dd, -ddd ) to increase the
19 detail of debug messages sent to syslog. Each extra d adds more
20 debugging information.
21 -f
23 Don't fork, run in the foreground.
24 -h
26 Show help information.
27 -l
29 Log through stdout and stderr instead of syslog. This option
30 works only with option -f, otherwise it is ignored.
31 -?
33 Show help information on stderr.
34 -R
36 Replace a running dmeventd instance. The running dmeventd must
37 be version 2.02.77 or newer. The new dmeventd instance will
38 obtain a list of devices and events to monitor from the cur‐
39 rently running daemon.
40 -V
42 Show version of dmeventd.
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45 Mirror
46 Attempts to handle device failure automatically. See
47 lvm.conf(5).
48 Raid
50 Attempts to handle device failure automatically. See
51 lvm.conf(5).
52 Snapshot
54 Monitors how full a snapshot is becoming and emits a warning to
55 syslog when it exceeds 80% full. The warning is repeated when
56 85%, 90% and 95% of the snapshot is filled. See lvm.conf(5).
57 Snapshot which runs out of space gets invalid and when it is
58 mounted, it gets umounted if possible.
59 Thin
61 Monitors how full a thin pool data and metadata is becoming and
62 emits a warning to syslog when it exceeds 80% full. The warning
63 is repeated when more then 85%, 90% and 95% of the thin pool is
64 filled. See lvm.conf(5). When a thin pool fills over 50% (data
65 or metadata) thin plugin calls configured dmeventd/thin_command
66 with every 5% increase. With default setting it calls internal
67 lvm lvextend --use-policies to resize thin pool when it's been
68 filled above configured threshold activation/thin_pool_autoex‐
69 tend_threshold. If the command fails, dmeventd thin plugin will
70 keep retrying execution with increasing time delay between
71 retries upto 42 minutes. User may also configure external com‐
72 mand to support more advanced maintenance operations of a thin
73 pool. Such external command can e.g. remove some unneeded snap‐
74 shots, use fstrim(8) to free recover space in a thin pool, but
75 also can use lvextend --use-policies if other actions have not
76 released enough space. Command is executed with environmental
77 variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 command executed in
78 this environment will not try to interact with dmeventd. To see
79 the fullness of a thin pool command may check these two environ‐
80 mental variables DMEVENTD_THIN_POOL_DATA and
81 DMEVENTD_THIN_POOL_METADATA. Command can also read status with
82 tools like lvs(8).
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85 DMEVENTD_THIN_POOL_DATA
86 Variable is set by thin plugin and is available to executed pro‐
87 gram. Value present actual usage of thin pool data volume. Vari‐
88 able is not set when error event is processed.
89 DMEVENTD_THIN_POOL_METADATA
91 Variable is set by thin plugin and is available to executed pro‐
92 gram. Value present actual usage of thin pool metadata volume.
93 Variable is not set when error event is processed.
94 LVM_RUN_BY_DMEVENTD
96 Variable is set by thin plugin to prohibit recursive interation
97 with dmeventd by any executed lvm2 command from a thin_command
98 environment.
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101 lvm(8), lvm.conf(5)
102Red Hat Inc DM TOOLS 2.03.02(2)-RHEL8 (2019-01-04) DMEVENTD(8)