1DMEVENTD(8)                 System Manager's Manual                DMEVENTD(8)
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NAME

6       dmeventd — Device-mapper event daemon
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SYNOPSIS

9       dmeventd [-d [-d [-d]]] [-f] [-h] [-l] [-R] [-V] [-?]
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DESCRIPTION

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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OPTIONS

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.
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21       -f     Don't fork, run in the foreground.
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23       -h     Show help information.
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25       -l     Log  through  stdout  and stderr instead of syslog.  This option
26              works only with option -f, otherwise it is ignored.
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28       -?     Show help information on stderr.
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30       -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.
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35       -V     Show version of dmeventd.
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LVM PLUGINS

38       Mirror Attempts to handle device failure automatically.
39              See lvm.conf(5).
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41       Raid   Attempts to handle device failure automatically.
42              See lvm.conf(5).
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44       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.
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51       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).
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73       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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ENVIRONMENT VARIABLES

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.
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100       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.
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105       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.
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110       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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SEE ALSO

116       lvm(8), lvm.conf(5), lvextend(8),
117       fstrim(8)
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121Red Hat Inc            DM TOOLS 2.03.22(2) (2023-08-02)            DMEVENTD(8)
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