GNU/Linux man pages
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GNU/Linux |
CentOS 5.5 |
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lvcreate(8) |
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lvcreate − create a logical volume in an existing volume group
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}
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.
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.
"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.
lvm(8), vgcreate(8), lvremove(8), lvrename(8) lvextend(8), lvreduce(8), lvdisplay(8), lvscan(8)
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lvcreate(8) | |