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140 lines
4.7 KiB
Groff
140 lines
4.7 KiB
Groff
.TH LVCREATE 8 "LVM TOOLS" "Sistina Software UK" \" -*- nroff -*-
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.SH NAME
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lvcreate \- create a logical volume in an existing volume group
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.SH SYNOPSIS
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.B lvcreate
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[\-\-addtag Tag]
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[\-\-alloc AllocationPolicy]
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[\-A/\-\-autobackup y/n] [\-C/\-\-contiguous y/n] [\-d/\-\-debug]
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[\-h/\-?/\-\-help]
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[\-i/\-\-stripes Stripes [\-I/\-\-stripesize StripeSize]]
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{\-l/\-\-extents LogicalExtentsNumber |
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\-L/\-\-size LogicalVolumeSize[kKmMgGtT]}
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[\-M/\-\-persistent y/n] [\-\-minor minor]
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[\-n/\-\-name LogicalVolumeName]
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[\-p/\-\-permission r/rw] [\-r/\-\-readahead ReadAheadSectors]
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[\-t/\-\-test]
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[\-v/\-\-verbose] [\-Z/\-\-zero y/n]
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VolumeGroupName [PhysicalVolumePath...]
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.br
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.br
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.B lvcreate
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{\-l/\-\-extents LogicalExtentsNumber |
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\-L/\-\-size LogicalVolumeSize[kKmMgGtT]}
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[\-c/\-\-chunksize ChunkSize]
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\-s/\-\-snapshot \-n/\-\-name SnapshotLogicalVolumeName OriginalLogicalVolumePath
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.SH DESCRIPTION
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lvcreate creates a new logical volume in a volume group ( see
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.B vgcreate(8), vgchange(8)
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) by allocating logical extents from the free physical extent pool
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of that volume group. If there are not enough free physical extents then
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the volume group can be extended ( see
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.B vgextend(8)
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) with other physical volumes or by reducing existing logical volumes
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of this volume group in size ( see
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.B lvreduce(8)
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).
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.br
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The second form supports the creation of snapshot logical volumes which
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keep the contents of the original logical volume for backup purposes.
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.SH OPTIONS
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See \fBlvm\fP for common options.
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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 \-C, \-\-contiguous y/n
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Sets or resets the contiguous allocation policy for
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logical volumes. Default is no contiguous allocation based
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on a next free principle.
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.TP
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.I \-i, \-\-stripes Stripes
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Gives the number of stripes.
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This is equal to the number of physical volumes to scatter
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the logical volume.
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.TP
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.I \-I, \-\-stripesize StripeSize
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Gives the number of kilobytes for the granularity of the stripes.
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.br
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StripeSize must be 2^n (n = 2 to 9)
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.TP
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.I \-l, \-\-extents LogicalExtentsNumber
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Gives the number of logical extents to allocate for the new
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logical volume.
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.TP
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.I \-L, \-\-size LogicalVolumeSize[kKmMgGtT]
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Gives the size to allocate for the new logical volume.
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A size suffix of K for kilobytes, M for megabytes,
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G for gigabytes or T for terabytes is optional.
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.br
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Default unit is megabytes.
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.TP
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.I \-\-minor minor
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Set the minor number.
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.TP
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.I \-M, \-\-persistent y/n
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Set to y to make the minor number specified persistent.
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.TP
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.I \-n, \-\-name LogicalVolumeName
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The name for the new logical volume.
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.br
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Without this option a default names of "lvol#" will be generated where
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# is the LVM internal number of the logical volume.
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.TP
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.I \-p, \-\-permission r/w
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Set access permissions to read only or read and write.
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.br
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Default is read and write.
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.TP
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.I \-r, \-\-readahead ReadAheadSectors
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Set read ahead sector count of this logical volume to a value between 2 and 120.
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Ignored by device-mapper.
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.TP
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.I \-s, \-\-snapshot
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Create a snapshot logical volume (or snapshot) for an existing, so called
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original logical volume (or origin).
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Snapshots provide a 'frozen image' of the contents of the origin
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while the origin can still be updated. They enable consistent
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backups and online recovery of removed/overwritten data/files. The snapshot
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does not need the same amount of storage the origin has. In a typical scenario,
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15-20% might be enough. In case the snapshot runs out of storage, use
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.B lvextend(8)
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to grow it. Shrinking a snapshot is supported by
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.B lvreduce(8)
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as well. Run
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.B lvdisplay(8)
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on the snapshot in order to check how much data is allocated to it.
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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 new logical volume.
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.br
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Default is yes.
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.br
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Warning: trying to mount an unzeroed logical volume can cause the system to
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hang.
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.SH Examples
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"lvcreate -i 3 -I 8 -L 100 vg00" tries to create a striped logical
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volume with 3 stripes, a stripesize of 8KB and a size of 100MB in the volume
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group named vg00. The logical volume name will be chosen by lvcreate.
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"lvcreate --size 100m --snapshot --name snap /dev/vg00/lvol1"
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.br
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creates a snapshot logical volume named /dev/vg00/snap which has access to the
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contents of the original logical volume named /dev/vg00/lvol1
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at snapshot logical volume creation time. If the original logical volume
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contains a file system, you can mount the snapshot logical volume on an
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arbitrary directory in order to access the contents of the filesystem to run
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a backup while the original filesystem continues to get updated.
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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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