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. Li‐
13 brary plugins can register and carry out actions triggered when partic‐
14 ular events occur.
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17 -d Repeat from 1 to 3 times (-d, -dd, -ddd) to increase the detail
18 of debug messages sent to syslog. Each extra d adds more debug‐
19 ging information.
20 -f Don't fork, run in the foreground.
22 -h Show help information.
24 -l Log through stdout and stderr instead of syslog. This option
26 works only with option -f, otherwise it is ignored.
27 -? Show help information on stderr.
29 -R Replace a running dmeventd instance. The running dmeventd must
31 be version 2.02.77 or newer. The new dmeventd instance will ob‐
32 tain a list of devices and events to monitor from the currently
33 running daemon.
34 -V Show version of dmeventd.
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38 Mirror Attempts to handle device failure automatically.
39 See lvm.conf(5).
40 Raid Attempts to handle device failure automatically.
42 See lvm.conf(5).
43 Snapshot
45 Monitors how full a snapshot is becoming and emits a warning to
46 syslog when it exceeds 80% full. The warning is repeated when
47 85%, 90% and 95% of the snapshot is filled. See lvm.conf(5).
48 Snapshot which runs out of space gets invalid and when it is
49 mounted, it gets umounted if possible.
50 Thin Monitors how full a thin pool data and metadata is becoming and
52 emits a warning to syslog when it exceeds 80% full. The warning
53 is repeated when more then 85%, 90% and 95% of the thin pool is
54 filled. See lvm.conf(5). When a thin pool fills over 50% (data
55 or metadata) thin plugin calls configured dmeventd/thin_command
56 with every 5% increase. With default setting it calls internal
57 lvm lvextend --use-policies to resize thin pool when it's been
58 filled above configured threshold activation/thin_pool_autoex‐
59 tend_threshold. If the command fails, dmeventd thin plugin will
60 keep retrying execution with increasing time delay between re‐
61 tries up to 42 minutes. User may also configure external com‐
62 mand to support more advanced maintenance operations of a thin
63 pool. Such external command can e.g. remove some unneeded snap‐
64 shots, use fstrim(8) to free recover space in a thin pool, but
65 also can use lvextend --use-policies if other actions have not
66 released enough space. Command is executed with environmental
67 variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 command executed in
68 this environment will not try to interact with dmeventd. To see
69 the fullness of a thin pool command may check these two environ‐
70 mental variables DMEVENTD_THIN_POOL_DATA and DMEVENTD_THIN_POOL_
71 METADATA. Command can also read status with tools like lvs(8).
72 Vdo Monitors how full a VDO pool data is becoming and emits a warn‐
74 ing to syslog when it exceeds 80% full. The warning is repeated
75 when more then 85%, 90% and 95% of the VDO pool is filled. See
76 lvm.conf(5). When a VDO pool fills over 50% vdo plugin calls
77 configured dmeventd/vdo_command with every 5% increase. With
78 default setting it calls internal lvm lvextend --use-policies to
79 resize VDO pool when it's been filled above the configured
80 threshold activation/vdo_pool_autoextend_threshold. If the com‐
81 mand fails, dmeventd vdo plugin will keep retrying execution
82 with increasing time delay between retries up to 42 minutes.
83 User may also configure external command to support more ad‐
84 vanced maintenance operations of a VDO pool. Such external com‐
85 mand can e.g. remove some unneeded space with fstrim(8), but
86 also can use lvextend --use-policies if other actions have not
87 released enough space. Command is executed with environmental
88 variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 command executed in
89 this environment will not try to interact with dmeventd. To see
90 the fullness of a VDO pool command may check this environmental
91 variable DMEVENTD_VDO_POOL. Command can also read status with
92 tools like lvs(8).
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95 DMEVENTD_THIN_POOL_DATA
96 Variable is set by thin plugin and is available to executed pro‐
97 gram. Value present actual usage of thin pool data volume. Vari‐
98 able is not set when error event is processed.
99 DMEVENTD_THIN_POOL_METADATA
101 Variable is set by thin plugin and is available to executed pro‐
102 gram. Value present actual usage of thin pool metadata volume.
103 Variable is not set when error event is processed.
104 DMEVENTD_VDO_POOL
106 Variable is set by vdo plugin and is available to executed pro‐
107 gram. Value present actual usage of VDO pool data volume. Vari‐
108 able is not set when error event is processed.
109 LVM_RUN_BY_DMEVENTD
111 Variable is set by thin and vdo plugin to prohibit recursive in‐
112 teraction with dmeventd by any executed lvm2 command from a
113 thin_command, vdo_command environment.
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116 lvm(8), lvm.conf(5), lvextend(8),
117 fstrim(8)
118Red Hat Inc DM TOOLS 2.03.22(2) (2023-08-02) DMEVENTD(8)