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234b12480e
Switch lvconvert's --merge code over to using process_each_lv(). Doing so adds support for a single 'lvconvert --merge' to start merging multiple LVs (which includes @tag expansion). Add 'lvconvert --merge @tag' testing to test/t-snapshot-merge.sh Adjust man/lvconvert.8.in to reflect these expanded capabilities. The lvconvert.c implementation requires rereading the VG each iteration of process_each_lv(). Otherwise a stale VG instance associated with the LV passed to lvconvert_single_merge() would result in stale VG metadata being written back out to disk. This overwrote new metadata that was written when a previous snapshot LV finished merging (via lvconvert_poll). This is only an issue when merging multiple LVs that share the same VG (a single VG is typical for most LVM configurations on system disks). In the end this new support is very useful for performing a "system rollback" that requires multiple snapshot LVs be merged to their respective origin LV. The yum-utils 'fs-snapshot' plugin tags all snapshot LVs that it creates with a common 'snapshot_tag' that is unique to the yum transaction. Rolling back a yum transaction, that created LVM snapshots with the tag 'yum_20100129133223', is as simple as: lvconvert --merge @yum_20100129133223 Signed-off-by: Mike Snitzer <snitzer@redhat.com>
221 lines
6.8 KiB
Groff
221 lines
6.8 KiB
Groff
.TH LVCONVERT 8 "LVM TOOLS #VERSION#" "Red Hat, Inc" \" -*- nroff -*-
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.SH NAME
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lvconvert \- convert a logical volume from linear to mirror or snapshot
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.SH SYNOPSIS
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.B lvconvert
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\-m|\-\-mirrors Mirrors [\-\-mirrorlog {disk|core}] [\-\-corelog] [\-R|\-\-regionsize MirrorLogRegionSize]
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[\-A|\-\-alloc AllocationPolicy]
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[\-b|\-\-background] [\-f|\-\-force] [\-i|\-\-interval Seconds]
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[\-h|\-?|\-\-help]
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[\-\-noudevsync]
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[\-v|\-\-verbose] [\-y|\-\-yes]
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[\-\-version]
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.br
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LogicalVolume[Path] [PhysicalVolume[Path][:PE[-PE]]...]
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.B lvconvert
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\-\-splitmirrors Images \-\-name SplitLogicalVolumeName
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MirrorLogicalVolume[Path] [SplittablePhysicalVolume[Path][:PE[-PE]]...]
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.B lvconvert
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\-s|\-\-snapshot [\-c|\-\-chunksize ChunkSize]
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[\-h|\-?|\-\-help]
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[\-\-noudevsync]
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[\-v|\-\-verbose]
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[\-Z|\-\-zero y|n]
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[\-\-version]
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.br
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OriginalLogicalVolume[Path] SnapshotLogicalVolume[Path]
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.B lvconvert
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\-\-merge [\-b|\-\-background] [\-i|\-\-interval Seconds]
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[\-h|\-?|\-\-help]
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[\-v|\-\-verbose]
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[\-\-version]
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SnapshotLogicalVolume[Path]...
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.B lvconvert
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\-\-repair
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[\-h|\-?|\-\-help]
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[\-v|\-\-verbose]
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[\-\-version]
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LogicalVolume[Path] [PhysicalVolume[Path]...]
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.SH DESCRIPTION
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lvconvert will change a linear logical volume to a mirror
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logical volume or to a snapshot of linear volume and vice versa.
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It is also used to add and remove disk logs from mirror devices.
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.br
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If the conversion requires allocation of physical extents (for
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example, when converting from linear to mirror) and you specify
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one or more PhysicalVolumes (optionally with ranges of physical
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extents), allocation of physical extents will be restricted to
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these physical extents. If the conversion frees physical extents
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(for example, when converting from a mirror to a linear, or reducing
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mirror legs) and you specify one or more PhysicalVolumes,
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the freed extents come first from the specified PhysicalVolumes.
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.SH OPTIONS
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See \fBlvm\fP for common options.
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.br
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Exactly one of \-\-splitmirrors, \-\-mirrors, \-\-repair, \-\-snapshot
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or \-\-merge arguments is required.
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.br
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.TP
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.I \-m, \-\-mirrors Mirrors
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Specifies the degree of the mirror you wish to create.
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For example, "-m 1" would convert the original logical
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volume to a mirror volume with 2-sides; that is, a
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linear volume plus one copy.
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.TP
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.I \-\-mirrorlog {disk|core}
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Specifies the type of log to use.
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The default is disk, which is persistent and requires
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a small amount of storage space, usually on a separate device
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from the data being mirrored.
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Core may be useful for short-lived mirrors: It means the mirror is
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regenerated by copying the data from the first device again every
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time the device is activated - perhaps, for example, after every reboot.
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.TP
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.I \-\-corelog
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The optional argument "--corelog" is the same as specifying "--mirrorlog core".
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.TP
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.I \-R, \-\-regionsize MirrorLogRegionSize
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A mirror is divided into regions of this size (in MB), and the mirror log
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uses this granularity to track which regions are in sync.
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.TP
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.I \-b, \-\-background
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Run the daemon in the background.
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.TP
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.I \-i, \-\-interval Seconds
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Report progress as a percentage at regular intervals.
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.br
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.TP
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.I \-\-noudevsync
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Disable udev synchronisation. The
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process will not wait for notification from udev.
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It will continue irrespective of any possible udev processing
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in the background. You should only use this if udev is not running
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or has rules that ignore the devices LVM2 creates.
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.br
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.TP
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.I \-\-splitmirrors Images
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The number of redundant Images of a mirror to be split off and used
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to form a new logical volume. A name must be supplied for the
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newly-split-off logical volume using the \-\-name argument.
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.TP
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.I \-n Name
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The name to apply to a logical volume which has been split off from
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a mirror logical volume.
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.br
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.TP
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.I \-s, \-\-snapshot
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Create a snapshot from existing logical volume using another
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existing logical volume as its origin.
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.TP
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.I \-c, \-\-chunksize ChunkSize
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Power of 2 chunk size for the snapshot logical volume between 4k and 512k.
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.TP
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.I \-Z, \-\-zero y|n
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Controls zeroing of the first KB of data in the snapshot.
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If the volume is read-only the snapshot will not be zeroed.
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.TP
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.I \-\-merge
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Merges a snapshot into its origin volume. If both the origin and snapshot volume
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are not open the merge will start immediately. Otherwise, the merge will start
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the first time either the origin or snapshot are activated and both are closed.
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Merging a snapshot into an origin that cannot be closed, for example a root
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filesystem, is deferred until the next time the origin volume is activated.
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When merging starts, the resulting logical volume will have the origin's name,
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minor number and UUID. While the merge is in progress, reads or writes to the
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origin appear as they were directed to the snapshot being merged. When the
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merge finishes, the merged snapshot is removed. Multiple snapshots may
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be specified on the commandline or a @tag may be used to specify
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multiple snapshots be merged to their respective origin.
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.br
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.TP
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.I \-\-repair
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Repair a mirror after suffering a disk failure. The mirror will be brought back
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into a consistent state. By default, the original number of mirrors will be
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restored if possible. Specify \-y on the command line to skip the prompts.
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Use \-f if you do not want any replacement. Additionally, you may use
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\-\-use-policies to use the device replacement policy specified in lvm.conf,
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viz. activation/mirror_log_fault_policy or
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activation/mirror_device_fault_policy.
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.br
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.SH Examples
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"lvconvert -m1 vg00/lvol1"
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.br
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converts the linear logical volume "vg00/lvol1" to
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a two-way mirror logical volume.
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"lvconvert --mirrorlog core vg00/lvol1"
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.br
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converts a mirror with a disk log to a
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mirror with an in-memory log.
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"lvconvert --mirrorlog disk vg00/lvol1"
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converts a mirror with an in-memory log
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to a mirror with a disk log.
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"lvconvert -m0 vg00/lvol1"
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converts a mirror logical volume to a linear logical
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volume.
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.br
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.br
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"lvconvert -s vg00/lvol1 vg00/lvol2"
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converts logical volume "vg00/lvol2" to snapshot of original volume "vg00/lvol1"
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"lvconvert -m1 vg00/lvol1 /dev/sda:0-15 /dev/sdb:0-15"
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converts linear logical volume "vg00/lvol1" to a two-way mirror, using physical
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extents /dev/sda:0-15 and /dev/sdb:0-15 for allocation of new extents.
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"lvconvert -m0 vg00/lvmirror1 /dev/sda
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converts mirror logical volume "vg00/lvmirror1" to linear, freeing physical
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extents from /dev/sda.
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.br
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"lvconvert --merge vg00/lvol1_snap"
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merges "vg00/lvol1_snap" into its origin.
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"lvconvert --merge @some_tag"
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If vg00/lvol1, vg00/lvol2, and vg00/lvol3 are all tagged with "some_tag"
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each snapshot logical volume will be merged serially, e.g.: vg00/lvol1,
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then vg00/lvol2, then vg00/lvol3. If --background were used it would start
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all snapshot logical volume merges in parallel.
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.SH SEE ALSO
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.BR lvm (8),
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.BR vgcreate (8),
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.BR lvremove (8),
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.BR lvrename (8),
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.BR lvextend (8),
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.BR lvreduce (8),
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.BR lvdisplay (8),
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.BR lvscan (8)
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