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] [-i|--stripes Stripes
[-I|--stripesize StripeSize]] {-l|--extents
LogicalExtentsNumber[%{VG|PVS|FREE}] |
-L|--size LogicalVolumeSize[kKmMgGtT]} [-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...]
lvcreate {-l|--extents LogicalExtentsNumber[%{VG|FREE}] |
-L|--size LogicalVolumeSize[kKmMgGtT]} [-c|--chunksize ChunkSize] -s|--snapshot
-n|--name SnapshotLogicalVolumeName OriginalLogicalVolumePath
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) ).
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[kKmMgGtTpPeE]
- 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.
- -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.
- -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.
SEE ALSO
lvm(8),
vgcreate(8),
lvremove(8),
lvrename(8)
lvextend(8),
lvreduce(8),
lvdisplay(8),
lvscan(8)