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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
213 lines
5.7 KiB
Plaintext
213 lines
5.7 KiB
Plaintext
.TH DMFILEMAPD 8 "Dec 17 2016" "Linux" "MAINTENANCE COMMANDS"
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.de OPT_FD
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. RB [ file_descriptor ]
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..
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.
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.de OPT_GROUP
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. RB [ group_id ]
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..
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.de OPT_PATH
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. RB [ abs_path ]
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..
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.
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.de OPT_MODE
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. RB [ mode ]
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..
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.
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.de OPT_DEBUG
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. RB [ foreground [ verbose ] ]
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..
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.
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.SH NAME
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dmfilemapd \(em device-mapper filemap monitoring daemon
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.
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.SH SYNOPSIS
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.
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.de CMD_DMFILEMAPD
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. ad l
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. IR dmfilemapd
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. OPT_FD
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. OPT_GROUP
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. OPT_PATH
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. OPT_MODE
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. OPT_DEBUG
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. ad b
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..
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.CMD_DMFILEMAPD
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.
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.PD
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.ad b
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.
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.SH DESCRIPTION
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.
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The dmfilemapd daemon monitors groups of \fIdmstats\fP regions that
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correspond to the extents of a file, adding and removing regions to
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reflect the changing state of the file on-disk.
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The daemon is normally launched automatically by the \fPdmstats
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create\fP command, but can be run manually, either to create a new
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daemon where one did not previously exist, or to change the options
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previously used, by killing the existing daemon and starting a new
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one.
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.
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.SH OPTIONS
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.HP
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.BR file_descriptor
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.br
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Specify the file descriptor number for the file to be monitored.
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The file descriptor must reference a regular file, open for reading,
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in a local file system that supports the FIEMAP ioctl, and that
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returns data describing the physical location of extents.
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The process that executes \fBdmfilemapd\fP is responsible for
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opening the file descriptor that is handed to the daemon.
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.
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.HP
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.BR group_id
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.br
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The \fBdmstats\fP group identifier of the group that \fBdmfilemapd\fP
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should update. The group must exist and it should correspond to
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a set of regions created by a previous filemap operation.
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.
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.HP
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.BR abs_path
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.br
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The absolute path to the file being monitored, at the time that
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it was opened. The use of \fBpath\fP by the daemon differs,
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depending on the filemap following mode in use; see \fBMODES\fP
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and the \fBmode\fP option for more information.
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.br
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.HP
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.BR mode
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.br
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The filemap monitoring mode the daemon should use: either "inode"
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(\fBDM_FILEMAP_FOLLOW_INODE\fP), or "path"
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(\fBDM_FILEMAP_FOLLOW_PATH\fP), to enable follow-inode or
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follow-path mode respectively.
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.
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.HP
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.BR [foreground]
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.br
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If set to 1, disable forking and allow the daemon to run in the
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foreground.
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.
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.HP
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.BR [verbose]
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Control daemon logging. If set to zero, the daemon will close all
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stdio streams and run silently. If \fBverbose\fP is a number
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between 1 and 3, stdio will be retained and the daemon will log
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messages to stdout and stderr that match the specified verbosity
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level.
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.
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.
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.SH MODES
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.
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The file map monitoring daemon can monitor files in two distinct
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ways: the mode affects the behaviour of the daemon when a file
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under monitoring is renamed or unlinked, and the conditions which
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cause the daemon to terminate.
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In both modes, the daemon will always shut down when the group
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being monitored is deleted.
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.P
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.B Follow inode
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.P
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The daemon follows the inode of the file, as it was at the time the
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daemon started. The file descriptor referencing the file is kept
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open at all times, and the daemon will exit when it detects that
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the file has been unlinked and it is the last holder of a reference
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to the file.
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This mode is useful if the file is expected to be renamed, or moved
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within the file system, while it is being monitored.
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.P
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.B Follow path
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.P
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The daemon follows the path that was given on the daemon command
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line. The file descriptor referencing the file is re-opened on each
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iteration of the daemon, and the daemon will exit if no file exists
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at this location (a tolerance is allowed so that a brief delay
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between removal and replacement is permitted).
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This mode is useful if the file is updated by unlinking the original
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and placing a new file at the same path.
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.
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.SH LIMITATIONS
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.
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The daemon attempts to maintain good synchronisation between the file
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extents and the regions contained in the group, however, since the
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daemon can only react to new allocations once they have been written,
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there are inevitably some IO events that cannot be counted when a
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file is growing, particularly if the file is being extended by a
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single thread writing beyond EOF (for example, the \fBdd\fP program).
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There is a further loss of events in that there is currently no way
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to atomically resize a \fBdmstats\fP region and preserve its current
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counter values. This affects files when they grow by extending the
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final extent, rather than allocating a new extent: any events that
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had accumulated in the region between any prior operation and the
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resize are lost.
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File mapping is currently most effective in cases where the majority
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of IO does not trigger extent allocation. Future updates may address
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these limitations when kernel support is available.
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.
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.SH EXAMPLES
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.
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Normally the daemon is started automatically by the \fBdmstats\fP
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\fBcreate\fP or \fBupdate_filemap\fP commands but it can be run
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manually for debugging or testing purposes.
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.P
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Start the daemon in the background, in follow-path mode
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.br
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#
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.B dmfilemapd 3 0 /srv/images/vm.img path 0 0 3< /srv/images/vm.img
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.br
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.P
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Start the daemon in follow-inode mode, disable forking and enable
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verbose logging
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.br
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#
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.B dmfilemapd 3 0 /var/tmp/data inode 1 3 3< /var/tmp/data
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.br
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Starting dmfilemapd with fd=3, group_id=0 mode=inode, path=/var/tmp/data
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.br
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dm version [ opencount flush ] [16384] (*1)
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.br
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dm info (253:0) [ opencount flush ] [16384] (*1)
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.br
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dm message (253:0) [ opencount flush ] @stats_list dmstats [16384] (*1)
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.br
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Read alias 'data' from aux_data
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.br
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Found group_id 0: alias="data"
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.br
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dm_stats_walk_init: initialised flags to 4000000000000
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.br
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starting stats walk with GROUP
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.br
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exiting _filemap_monitor_get_events() with deleted=0, check=0
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.br
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Waiting for check interval
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.br
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.P
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.
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.SH AUTHORS
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.
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Bryn M. Reeves <bmr@redhat.com>
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.
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.SH SEE ALSO
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.
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.BR dmstats (8)
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LVM2 resource page: https://www.sourceware.org/lvm2/
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.br
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Device-mapper resource page: http://sources.redhat.com/dm/
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.br
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