1LVMETAD(8) System Manager's Manual LVMETAD(8)
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6 lvmetad — LVM metadata cache daemon
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10 lvmetad [-l level[,level...]] [-p pidfile_path] [-s socket_path] [-t
11 timeout_value] [-f] [-h] [-V] [-?]
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15 The lvmetad daemon caches LVM metadata so that LVM commands can read
16 metadata from the cache rather than scanning disks. This can be an
17 advantage because scanning disks is time consuming and may interfere
18 with the normal work of the system. lvmetad can be a disadvantage when
19 disk event notifications from the system are unreliable.
20 lvmetad does not read metadata from disks itself. Instead, it relies
22 on an LVM command, like pvscan --cache, to read metadata from disks and
23 send it to lvmetad to be cached.
24 New LVM disks that appear on the system must be scanned before lvmetad
26 knows about them. If lvmetad does not know about a disk, then LVM com‐
27 mands using lvmetad will also not know about it. When disks are added
28 or removed from the system, lvmetad must be updated.
29 lvmetad is usually combined with event-based system services that auto‐
31 matically run pvscan --cache on disks added or removed. This way, the
32 cache is automatically updated with metadata from new disks when they
33 appear. LVM udev rules and systemd services implement this automation.
34 Automatic scanning is usually combined with automatic activation. For
35 more information, see pvscan(8).
36 If lvmetad is started or restarted after disks have been added to the
38 system, or if the global_filter has changed, the cache must be updated.
39 This can be done by running pvscan --cache, or it will be done automat‐
40 ically by the next LVM command that's run.
41 When lvmetad is not used, LVM commands revert to scanning disks for LVM
43 metadata.
44 In some cases, lvmetad will be temporarily disabled while it continues
46 running. In this state, LVM commands will ignore the lvmetad cache and
47 revert to scanning disks. A warning will also be printed which
48 includes the reason why lvmetad is not being used. The most common
49 reasons are the existence of duplicate PVs (lvmetad cannot cache data
50 for duplicate PVs), or an 'lvconvert --repair' command has been run
51 (the lvmetad cache may not be reliable while repairs are neeeded.)
52 Once duplicates have been resolved, or repairs have been completed, the
53 lvmetad cache is can be updated with pvscan --cache and commands will
54 return to using the cache.
55 Use of lvmetad is enabled/disabled by:
57 lvm.conf(5) global/use_lvmetad
58 For more information on this setting, see:
60 lvmconfig --withcomments global/use_lvmetad
61 To ignore disks from LVM at the system level, e.g. lvmetad, pvscan use:
63 lvm.conf(5) devices/global_filter
64 For more information on this setting, see
66 lvmconfig --withcomments devices/global_filter
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70 To run the daemon in a test environment both the pidfile_path and the
71 socket_path should be changed from the defaults.
72 -f Don't fork, but run in the foreground.
74 -h, -? Show help information.
76 -l levels
78 Specify the levels of log messages to generate as a comma sepa‐
79 rated list. Messages are logged by syslog. Additionally, when
80 -f is given they are also sent to standard error. Possible lev‐
81 els are: all, fatal, error, warn, info, wire, debug.
82 -p pidfile_path
84 Path to the pidfile. This overrides both the built-in default
85 (/run/lvmetad.pid) and the environment variable LVM_LVMETAD_PID‐
86 FILE. This file is used to prevent more than one instance of
87 the daemon running simultaneously.
88 -s socket_path
90 Path to the socket file. This overrides both the built-in
91 default (/run/lvm/lvmetad.socket) and the environment variable
92 LVM_LVMETAD_SOCKET. To communicate successfully with lvmetad,
93 all LVM2 processes should use the same socket path.
94 -t timeout_value
96 The daemon may shutdown after being idle for the given time (in
97 seconds). When the option is omitted or the value given is zero
98 the daemon never shutdowns on idle.
99 -V Display the version of lvmetad daemon.
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103 LVM_LVMETAD_PIDFILE
104 Path for the pid file.
105 LVM_LVMETAD_SOCKET
107 Path for the socket file.
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111 lvm(8), lvmconfig(8), lvm.conf(5), pvscan(8)
112Red Hat Inc LVM TOOLS 2.02.183(2) (2018-12-07) LVMETAD(8)