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36cac41115
Commitsa29bb6a14b...5c199d99f4narrowed down on addressing the escaping of hyphens in the dynamic creation of manuals whilst avoiding them in creating help texts. This lead to a sequence of slipping through hyphens adrressed by additional patches in aforementioned commit series. On the other hand, postprocessing dynamically man-generator created and statically provided manuals catches all hyphens in need of escaping. Changes: - revert the above commits whilst keeping man-generator streamlining and the detection of any '\' when generating help texts in order to avoid escapes to slip in - Dynamically escape hyphens in manaual pages using sed(1) in the respective Makefile targets - remove any manually added escaping on hyphens from any static manual sources or headers
94 lines
3.7 KiB
Plaintext
94 lines
3.7 KiB
Plaintext
pvscan scans all supported LVM block devices in the system for PVs.
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\fBScanning with lvmetad\fP
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pvscan operates differently when used with the
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.BR lvmetad (8)
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daemon.
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Scanning disks is required to read LVM metadata and identify LVM PVs.
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Once read, lvmetad caches the metadata so that LVM commands can read it
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without repeatedly scanning disks. This is helpful because scanning disks
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is time consuming, and frequent scanning may interfere with the normal
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work of the system and disks.
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When lvmetad is not used, LVM commands revert to scanning disks to read
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metadata. Any LVM command that needs metadata will scan disks for it;
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running the pvscan command is not necessary for the sake of other LVM
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commands.
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When lvmetad is used, LVM commands avoid scanning disks by reading
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metadata from lvmetad. When new disks appear, they must be scanned so
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their metadata can be cached in lvmetad. This is done by the command
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pvscan --cache, which scans disks and passes the metadata to lvmetad.
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The pvscan --cache command is typically run automatically by system
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services when a new device appears. Users do not generally need to run
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this command if the system and lvmetad are running properly.
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Many scripts contain unnecessary pvscan (or vgscan) commands for
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historical reasons. To avoid disrupting the system with extraneous disk
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scanning, an ordinary pvscan (without --cache) will simply read metadata
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from lvmetad like other LVM commands. It does not do anything beyond
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displaying the current state of the cache.
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.IP \[bu] 2
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When given specific device name arguments, pvscan --cache will only
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read the named devices.
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.IP \[bu] 2
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LVM udev rules and systemd services are used to initiate automatic device
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scanning.
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.IP \[bu] 2
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To prevent devices from being scanned by pvscan --cache, add them
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to
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.BR lvm.conf (5)
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.B devices/global_filter.
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The devices/filter setting does not
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apply to system level scanning.
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For more information, see:
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.br
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.B lvmconfig --withcomments devices/global_filter
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.IP \[bu] 2
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If lvmetad is started or restarted after devices are visible, or
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if the global_filter has changed, then all devices must be rescanned
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for metadata with the command pvscan --cache.
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.IP \[bu] 2
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lvmetad does not cache older metadata formats, e.g. lvm1, and will
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be temporarily disabled if they are seen.
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.IP \[bu] 2
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To notify lvmetad about a device that is no longer present, the major and
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minor numbers must be given, not the path.
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.P
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\fBAutomatic activation\fP
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When event-driven system services detect a new LVM device, the first step
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is to automatically scan and cache the metadata from the device. This is
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done by pvscan --cache. A second step is to automatically activate LVs
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that are present on the new device. This auto-activation is done by the
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same pvscan --cache command when the option '-a|--activate ay' is
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included.
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Auto-activation of VGs or LVs can be enabled/disabled using:
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.br
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.BR lvm.conf (5)
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.B activation/auto_activation_volume_list
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For more information, see:
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.br
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.B lvmconfig --withcomments activation/auto_activation_volume_list
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When this setting is undefined, all LVs are auto-activated (when lvm is
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fully integrated with the event-driven system services.)
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When a VG or LV is not auto-activated, traditional activation using
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vgchange or lvchange -a|--activate is needed.
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.IP \[bu] 2
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pvscan auto-activation can be only done in combination with --cache.
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.IP \[bu] 2
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Auto-activation is designated by the "a" argument in '-a|--activate ay'.
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This is meant to distinguish system generated commands from explicit user
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commands, although it can be used in any activation command. Whenever it
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is used, the auto_activation_volume_list is applied.
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.IP \[bu] 2
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Auto-activation is not yet supported for LVs that are part of partial or
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clustered volume groups.
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