lvm2/man/lvcreate.8

.TH LVCREATE 8 "LVM TOOLS" "Sistina Software UK" \" -*- nroff -*-
.SH NAME
lvcreate \- create a logical volume in an existing volume group
.SH SYNOPSIS
.B lvcreate
[\-A/\-\-autobackup y/n] [\-C/\-\-contiguous y/n] [\-d/\-\-debug]
[\-h/\-?/\-\-help]
[\-i/\-\-stripes Stripes [\-I/\-\-stripesize StripeSize]]
{\-l/\-\-extents LogicalExtentsNumber |
 \-L/\-\-size LogicalVolumeSize[kKmMgGtT]}
[\-n/\-\-name LogicalVolumeName]
[\-p/\-\-permission r/rw] [\-r/\-\-readahead ReadAheadSectors]
[\-v/\-\-verbose] [\-Z/\-\-zero y/n]
VolumeGroupName [PhysicalVolumePath...]
.br

.br
.B lvcreate
{\-l/\-\-extents LogicalExtentsNumber |
 \-L/\-\-size LogicalVolumeSize[kKmMgGtT]}
[\-c/\-\-chunksize ChunkSize]
\-s/\-\-snapshot \-n/\-\-name SnapshotLogicalVolumeName OriginalLogicalVolumePath
.SH DESCRIPTION
lvcreate creates a new logical volume in a volume group ( see
.B vgcreate(8), vgchange(8)
) by allocating logical extents from the free physical extent pool
of that volume group.  If there are not enough free physical extents then
the volume group can be extended ( see
.B vgextend(8)
) with other physical volumes or by reducing existing logical volumes
of this volume group in size ( see
.B lvreduce(8), e2fsadm(8)
).
.br
The second form supports the creation of snapshot logical volumes which 
keep the contents of the original logical volume for backup purposes.
.SH OPTIONS
See \fBlvm\fP for common options.
.TP
.I \-A, \-\-autobackup y/n
Controls automatic backup of VG metadata after the change ( see
.B vgcfgbackup(8)
).
.br
Default is yes.
.TP
.I \-c, \-\-chunksize ChunkSize
Power of 2 chunk size for the snapshot logical volume between 4k and 1024k.
.TP
.I \-C, \-\-contiguous y/n
Sets or resets the contiguous allocation policy for
logical volumes. Default is no contiguous allocation based
on a next free principle.
.TP
.I \-i, \-\-stripes Stripes
Gives the number of stripes.
This is equal to the number of physical volumes to scatter
the logical volume.
.TP
.I \-I, \-\-stripesize StripeSize
Gives the number of kilobytes for the granularity of the stripes.
.br
StripeSize must be 2^n (n = 2 to 9)
.TP
.I \-l, \-\-extents LogicalExtentsNumber
Gives the number of logical extents to allocate for the new
logical volume.
.TP
.I \-L, \-\-size LogicalVolumeSize[kKmMgGtT]
Gives the size to allocate for the new logical volume.
A size suffix of K for kilobytes, M for megabytes,
G for gigabytes or T for terabytes is optional.
.br
Default unit is megabytes.
.TP
.I \-n, \-\-name LogicalVolumeName
The name for the new logical volume.
.br
Without this option a default names of "lvol#" will be generated where
# is the LVM internal number of the logical volume.
.TP
.I \-p, \-\-permission r/w
Set access permissions to read only or read and write.
.br
Default is read and write.
.TP
.I \-r, \-\-readahead ReadAheadSectors
Set read ahead sector count of this logical volume to a value between 2 and 120.
.TP
.I \-s, \-\-snapshot
Create a snapshot logical volume (or snapshot) for an existing, so called
original logical volume (or origin).
Snapshots provide a 'frozen image' of the contents of the origin
while the origin can still be updated. They enable consistent
backups and online recovery of removed/overwritten data/files. The snapshot
does not need the same amount of storage the origin has. In a typical scenario,
15-20% might be enough. In case the snapshot runs out of storage, use
.B lvextend(8)
to grow it. Shrinking a snapshot is supported by
.B lvreduce(8)
as well. Run
.B lvdisplay(8)
on the snapshot in order to check how much data is allocated to it.
.TP
.I \-Z, \-\-zero y/n
Controls zeroing of the first KB of data in the new logical volume.
.br
Default is yes.

.br
Warning: trying to mount an unzeroed logical volume can cause the system to
hang.
.SH Examples
"lvcreate -i 3 -I 8 -L 100 vg00" tries to create a striped logical
volume with 3 stripes, a stripesize of 8KB and a size of 100MB in the volume
group named vg00. The logical volume name will be chosen by lvcreate.

"lvcreate --size 100m --snapshot --name snap /dev/vg00/lvol1"
.br
creates a snapshot logical volume named /dev/vg00/snap which has access to the
contents of the original logical volume named /dev/vg00/lvol1
at snapshot logical volume creation time. If the original logical volume
contains a file system, you can mount the snapshot logical volume on an
arbitrary directory in order to access the contents of the filesystem to run
a backup while the original filesystem is updated.

.SH SEE ALSO
.BR lvm (8), 
.BR vgcreate (8), 
.BR lvremove (8), 
.BR lvrename (8)
.BR lvextend (8), 
.BR lvreduce (8), 
.BR lvdisplay (8), 
.BR lvscan (8)