NAME
lvcreate - create a logical volume in an existing volume group
SYNOPSIS
lvcreate [--addtag Tag] [--alloc AllocationPolicy] [-A|--autobackup
y|n] [-C|--contiguous y|n] [-d|--debug] [-h|-?|--help] [--noudevsync]
[-i|--stripes Stripes [-I|--stripesize StripeSize]] {-l|--extents
LogicalExtentsNumber[%{VG|PVS|FREE}] |
-L|--size LogicalVolumeSize[bBsSkKmMgGtTpPeE]} [-M|--persistent y|n]
[--minor minor] [-m|--mirrors Mirrors [--nosync] [--mirrorlog
{disk|core}] [--corelog] [-R|--regionsize MirrorLogRegionSize]]
[-n|--name LogicalVolumeName] [-p|--permission r|rw] [-r|--readahead
ReadAheadSectors|auto|none] [-t|--test] [-v|--verbose] [-Z|--zero y|n]
VolumeGroupName [PhysicalVolumePath[:PE[-PE]]...]
lvcreate {-l|--extents LogicalExtentsNumber[%{VG|FREE}] |
-L|--size LogicalVolumeSize[bBsSkKmMgGtTpPeE]} [-c|--chunksize
ChunkSize] [--noudevsync] -n|--name SnapshotLogicalVolumeName
{{-s|--snapshot} OriginalLogicalVolumePath | [-s|--snapshot]
VolumeGroupName --virtualsize VirtualSize}
DESCRIPTION
lvcreate creates a new logical volume in a volume group ( see
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
vgextend(8) ) with other physical volumes or by reducing existing
logical volumes of this volume group in size ( see lvreduce(8) ). If
you specify one or more PhysicalVolumes, allocation of physical extents
will be restricted to these volumes.
The second form supports the creation of snapshot logical volumes which
keep the contents of the original logical volume for backup purposes.
OPTIONS
See lvm for common options.
-c, --chunksize ChunkSize
Power of 2 chunk size for the snapshot logical volume between 4k
and 512k.
-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.
-i, --stripes Stripes
Gives the number of stripes. This is equal to the number of
physical volumes to scatter the logical volume.
-I, --stripesize StripeSize
Gives the number of kilobytes for the granularity of the
stripes.
StripeSize must be 2^n (n = 2 to 9) for metadata in LVM1 format.
For metadata in LVM2 format, the stripe size may be a larger
power of 2 but must not exceed the physical extent size.
-l, --extents LogicalExtentsNumber[%{VG|PVS|FREE}]
Gives the number of logical extents to allocate for the new
logical volume. This can also be expressed as a percentage of
the total space in the Volume Group with the suffix %VG, of the
remaining free space in the Volume Group with the suffix %FREE,
or of the remaining free space for the specified
PhysicalVolume(s) with the suffix %PVS,
-L, --size LogicalVolumeSize[bBsSkKmMgGtTpPeE]
Gives the size to allocate for the new logical volume. A size
suffix of K for kilobytes, M for megabytes, G for gigabytes, T
for terabytes, P for petabytes or E for exabytes is optional.
Default unit is megabytes.
--minor minor
Set the minor number.
-M, --persistent y|n
Set to y to make the minor number specified persistent.
-m, --mirrors Mirrors
Creates a mirrored logical volume with Mirrors copies. For
example, specifying "-m 1" would result in a mirror with two-
sides; that is, a linear volume plus one copy.
Specifying the optional argument --nosync will cause the
creation of the mirror to skip the initial resynchronization.
Any data written afterwards will be mirrored, but the original
contents will not be copied. This is useful for skipping a
potentially long and resource intensive initial sync of an empty
device.
The optional argument --mirrorlog specifies the type of log to
be used. The default is disk, which is persistent and requires
a small amount of storage space, usually on a separate device
from the data being mirrored. Using core means the mirror is
regenerated by copying the data from the first device again each
time the device is activated, for example, after every reboot.
The optional argument --corelog is equivalent to --mirrorlog
core.
-n, --name LogicalVolumeName
The name for the new logical volume.
Without this option a default names of "lvol#" will be generated
where # is the LVM internal number of the logical volume.
--noudevsync
Disable udev synchronisation. The process will not wait for
notification from udev. It will continue irrespective of any
possible udev processing in the background. You should only use
this if udev is not running or has rules that ignore the devices
LVM2 creates.
-p, --permission r|rw
Set access permissions to read only or read and write.
Default is read and write.
-r, --readahead ReadAheadSectors|auto|none
Set read ahead sector count of this logical volume. For volume
groups with metadata in lvm1 format, this must be a value
between 2 and 120. The default value is "auto" which allows the
kernel to choose a suitable value automatically. "None" is
equivalent to specifying zero.
-R, --regionsize MirrorLogRegionSize
A mirror is divided into regions of this size (in MB), and the
mirror log uses this granularity to track which regions are in
sync.
-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 lvextend(8) to grow it. Shrinking a
snapshot is supported by lvreduce(8) as well. Run lvdisplay(8)
on the snapshot in order to check how much data is allocated to
it. Note that a small amount of the space you allocate to the
snapshot is used to track the locations of the chunks of data,
so you should allocate slightly more space than you actually
need and monitor the rate at which the snapshot data is growing
so you can avoid running out of space.
--virtualsize VirtualSize
Create a sparse device of the given size (in MB by default)
using a snapshot. Anything written to the device will be
returned when reading from it. Reading from other areas of the
device will return blocks of zeros. It is implemented by
creating a hidden virtual device of the requested size using the
zero target. A suffix of _vorigin is used for this device.
-Z, --zero y|n
Controls zeroing of the first KB of data in the new logical
volume.
Default is yes.
Volume will not be zeroed if read only flag is set.
Snapshot volumes are zeroed always.
Warning: trying to mount an unzeroed logical volume can cause
the system to hang.
Examples
"lvcreate -i 3 -I 8 -L 100M 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 -m1 -L 500M vg00" tries to create a mirror logical volume
with 2 sides with a useable size of 500 MiB. This operation would
require 3 devices - two for the mirror devices and one for the disk
log.
"lvcreate -m1 --mirrorlog core -L 500M vg00" tries to create a mirror
logical volume with 2 sides with a useable size of 500 MiB. This
operation would require 2 devices - the log is "in-memory".
"lvcreate --size 100m --snapshot --name snap /dev/vg00/lvol1"
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 continues to get updated.
"lvcreate --virtualsize 1T --size 100M --snapshot --name sparse vg1"
creates a sparse device named /dev/vg1/sparse of size 1TB with space
for just under 100MB of actual data on it.
"lvcreate -L 64M -n lvol1 vg00 /dev/sda:0-7 /dev/sdb:0-7"
creates a linear logical volume "vg00/lvol1" using physical extents
/dev/sda:0-7 and /dev/sdb:0-7 for allocation of extents.
SEE ALSO
lvm(8), vgcreate(8), lvremove(8), lvrename(8) lvextend(8), lvreduce(8),
lvdisplay(8), lvscan(8)