Setting the Partition Type

If you are using a whole disk device for your physical volume, the disk must have no partition table. For DOS disk partitions, the partition id should be set to 0x8e using the fdisk or cfdiskcommand or an equivalent. For whole disk devices only the partition table must be erased, which will effectively destroy all data on that disk. You can remove an existing partition table by zeroing the first sector with the following command:

# dd if=/dev/zero of=PhysicalVolume bs=512 count=1

Initializing Physical Volumes

Use the pvcreate command to initialize a block device to be used as a physical volume. Initialization is analogous to formatting a file system.

The following command initializes /dev/sdd, /dev/sde, and /dev/sdf as LVM physical volumes for later use as part of LVM logical volumes.

# pvcreate /dev/sdd /dev/sde /dev/sdf

To initialize partitions rather than whole disks: run the pvcreate command on the partition. The following example initializes the partition /dev/hdb1 as an LVM physical volume for later use as part of an LVM logical volume.

# pvcreate /dev/hdb1

Scanning for Block Devices

You can scan for block devices that may be used as physical volumes with the lvmdiskscancommand, as shown in the following example.

# lvmdiskscan
/dev/ram0                    [       16.00 MB]
  /dev/sda                     [       17.15 GB]
  /dev/root                    [       13.69 GB]
  /dev/ram                     [       16.00 MB]
  /dev/sda1                    [       17.14 GB] LVM physical volume
  /dev/VolGroup00/LogVol01     [      512.00 MB]
  /dev/ram2                    [       16.00 MB]
  /dev/new_vg/lvol0            [       52.00 MB]
  /dev/ram3                    [       16.00 MB]
  /dev/pkl_new_vg/sparkie_lv   [        7.14 GB]
  /dev/ram4                    [       16.00 MB]
  /dev/ram5                    [       16.00 MB]
  /dev/ram6                    [       16.00 MB]
  /dev/ram7                    [       16.00 MB]
  /dev/ram8                    [       16.00 MB]
  /dev/ram9                    [       16.00 MB]
  /dev/ram10                   [       16.00 MB]
  /dev/ram11                   [       16.00 MB]
  /dev/ram12                   [       16.00 MB]
  /dev/ram13                   [       16.00 MB]
  /dev/ram14                   [       16.00 MB]
  /dev/ram15                   [       16.00 MB]
  /dev/sdb                     [       17.15 GB]
  /dev/sdb1                    [       17.14 GB] LVM physical volume
  /dev/sdc                     [       17.15 GB]
  /dev/sdc1                    [       17.14 GB] LVM physical volume
  /dev/sdd                     [       17.15 GB]
  /dev/sdd1                    [       17.14 GB] LVM physical volume
  7 disks
  17 partitions
  0 LVM physical volume whole disks
  4 LVM physical volumes

Displaying Physical Volumes

There are three commands you can use to display properties of LVM physical volumes: pvs, pvdisplay, and pvscan.

The pvs command provides physical volume information in a configurable form, displaying one line per physical volume. The pvs command provides a great deal of format control, and is useful for scripting.

The pvdisplay command provides a verbose multi-line output for each physical volume. It displays physical properties (size, extents, volume group, etc.) in a fixed format.

The following example shows the output of the pvdisplay command for a single physical volume.

# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               new_vg
  PV Size               17.14 GB / not usable 3.40 MB
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              4388
  Free PE               4375
  Allocated PE          13
  PV UUID               Joqlch-yWSj-kuEn-IdwM-01S9-XO8M-mcpsVe

The pvscan command scans all supported LVM block devices in the system for physical volumes.

The following command shows all physical devices found:

# pvscan
 PV /dev/sdb2   VG vg0   lvm2 [964.00 MB / 0   free]
 PV /dev/sdc1   VG vg0   lvm2 [964.00 MB / 428.00 MB free]
 PV /dev/sdc2            lvm2 [964.84 MB]
 Total: 3 [2.83 GB] / in use: 2 [1.88 GB] / in no VG: 1 [964.84 MB]

Preventing Allocation on a Physical Volume

You can prevent allocation of physical extents on the free space of one or more physical volumes with the pvchange command. This may be necessary if there are disk errors, or if you will be removing the physical volume.

The following command disallows the allocation of physical extents on /dev/sdk1.

# pvchange -x n /dev/sdk1

You can also use the -xy arguments of the pvchange command to allow allocation where it had previously been disallowed.

Resizing a Physical Volume

If you need to change the size of an underlying block device for any reason, use the pvresizecommand to update LVM with the new size. You can execute this command while LVM is using the physical volume.

Removing Physical Volumes

If a device is no longer required for use by LVM, you can remove the LVM label with the `pvremove` command. Executing the `pvremove` command zeroes the LVM metadata on an empty physical volume.

# pvremove /dev/ram15
  Labels on physical volume "/dev/ram15" successfully wiped

Volume Group Administration

reating Volume Groups

To create a volume group from one or more physical volumes, use the vgcreate command. Thevgcreate command creates a new volume group by name and adds at least one physical volume to it.

The following command creates a volume group named vg1 that contains physical volumes /dev/sdd1 and /dev/sde1.

# vgcreate vg1 /dev/sdd1 /dev/sde1

When physical volumes are used to create a volume group, its disk space is divided into 4 MB extents, by default. This extent is the minimum amount by which the logical volume may be increased or decreased in size.

Creating Volume Groups in a Cluster

You create volume groups in a cluster environment with the vgcreate command, just as you create them on a single node.

By default, volume groups created with CLVM on shared storage are visible to all computers that have access to the shared storage. It is possible, however, to create volume groups that are local, visible only to one node in the cluster, by using the -c n of the vgcreate command.

The following command, when executed in a cluster environment, creates a volume group that is local to the node from which the command was executed. The command creates a local volume named vg1 that contains physical volumes /dev/sdd1 and /dev/sde1.

#  vgcreate -c n vg1 /dev/sdd1 /dev/sde1

You can change whether an existing volume group is local or clustered with the -c option of the vgchange command

You can check whether an existing volume group is a clustered volume group with the vgscommand, which displays the c attribute if the volume is clustered. The following command displays the attributes of the volume groups VolGroup00 and testvg1. In this example, VolGroup00 is not clustered, while testvg1 is clustered, as indicated by the c attribute under the Attr heading.

# vgs
  VG            #PV #LV #SN Attr   VSize  VFree
  VolGroup00      1   2   0 wz--n- 19.88G    0
  testvg1         1   1   0 wz--nc 46.00G 8.00M

Adding Physical Volumes to a Volume Group

To add additional physical volumes to an existing volume group, use the vgextend command. The vgextend command increases a volume group's capacity by adding one or more free physical volumes.

The following command adds the physical volume /dev/sdf1 to the volume group vg1.

# vgextend vg1 /dev/sdf1

Displaying Volume Groups

There are two commands you can use to display properties of LVM volume groups: vgs and vgdisplay.

The vgscan command, which scans all the disks for volume groups and rebuilds the LVM cache file, also displays the volume groups.

The vgs command provides volume group information in a configurable form, displaying one line per volume group. The vgs command provides a great deal of format control, and is useful for scripting.

The vgdisplay command displays volume group properties (such as size, extents, number of physical volumes, etc.) in a fixed form. The following example shows the output of a vgdisplay command for the volume group new_vg. If you do not specify a volume group, all existing volume groups are displayed.

# vgdisplay new_vg
  --- Volume group ---
  VG Name               new_vg
  System ID
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  11
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               51.42 GB
  PE Size               4.00 MB
  Total PE              13164
  Alloc PE / Size       13 / 52.00 MB
  Free  PE / Size       13151 / 51.37 GB
  VG UUID               jxQJ0a-ZKk0-OpMO-0118-nlwO-wwqd-fD5D32

Scanning Disks for Volume Groups to Build the Cache File

The vgscan command scans all supported disk devices in the system looking for LVM physical volumes and volume groups. This builds the LVM cache in the /etc/lvm/.cache file, which maintains a listing of current LVM devices.

LVM runs the vgscan command automatically at system startup and at other times during LVM operation, such as when you execute a vgcreate command or when LVM detects an inconsistency.

You may need to run the vgscan command manually when you change your hardware configuration and add or delete a device from a node, causing new devices to be visible to the system that were not present at system bootup. This may be necessary, for example, when you add new disks to the system on a SAN or hotplug a new disk that has been labeled as a physical volume.

The following example shows the output of a vgscan command.

# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "new_vg" using metadata type lvm2
  Found volume group "officevg" using metadata type lvm2

Removing Physical Volumes from a Volume Group

To remove unused physical volumes from a volume group, use the vgreduce command. The vgreduce command shrinks a volume group's capacity by removing one or more empty physical volumes. This frees those physical volumes to be used in different volume groups or to be removed from the system.

Before removing a physical volume from a volume group, you can make sure that the physical volume is not used by any logical volumes by using the pvdisplay command.

# pvdisplay /dev/hda1

-- Physical volume ---
PV Name               /dev/hda1
VG Name               myvg
PV Size               1.95 GB / NOT usable 4 MB [LVM: 122 KB]
PV#                   1
PV Status             available
Allocatable           yes (but full)
Cur LV                1
PE Size (KByte)       4096
Total PE              499
Free PE               0
Allocated PE          499
PV UUID               Sd44tK-9IRw-SrMC-MOkn-76iP-iftz-OVSen7

If the physical volume is still being used you will have to migrate the data to another physical volume using the pvmove command. Then use the vgreduce command to remove the physical volume:

The following command removes the physical volume /dev/hda1 from the volume group my_volume_group.

# vgreduce my_volume_group /dev/hda1

Changing the Parameters of a Volume Group

The vgchange command is used to deactivate and activate volume groups. You can also use this command to change several volume group parameters for an existing volume group.

The following command changes the maximum number of logical volumes of volume group vg00to 128.

# vgchange -l 128 /dev/vg00

For a description of the volume group parameters you can change with the vgchange command, see the vgchange(8) man page.

Activating and Deactivating Volume Groups

When you create a volume group it is, by default, activated. This means that the logical volumes in that group are accessible and subject to change.

There are various circumstances for which you need to make a volume group inactive and thus unknown to the kernel. To deactivate or activate a volume group, use the -a (--available) argument of the vgchange command.

The following example deactivates the volume group my_volume_group.

# vgchange -a n my_volume_group

If clustered locking is enabled, add ’e’ to activate or deactivate a volume group exclusively on one node or ’l’ to activate or/deactivate a volume group only on the local node. Logical volumes with single-host snapshots are always activated exclusively because they can only be used on one node at once.

Removing Volume Groups

To remove a volume group that contains no logical volumes, use the vgremove command.

# vgremove officevg
  Volume group "officevg" successfully removed

Splitting a Volume Group

To split the physical volumes of a volume group and create a new volume group, use the vgsplit command.

Logical volumes cannot be split between volume groups. Each existing logical volume must be entirely on the physical volumes forming either the old or the new volume group. If necessary, however, you can use the pvmove command to force the split.

The following example splits off the new volume group smallvg from the original volume groupbigvg.

# vgsplit bigvg smallvg /dev/ram15
  Volume group "smallvg" successfully split from "bigvg"

Combining Volume Groups

To combine two volume groups into a single volume group, use the vgmerge command. You can merge an inactive "source" volume with an active or an inactive "destination" volume if the physical extent sizes of the volume are equal and the physical and logical volume summaries of both volume groups fit into the destination volume groups limits.

The following command merges the inactive volume group my_vg into the active or inactive volume group databases giving verbose runtime information.

# vgmerge -v databases my_vg

Backing Up Volume Group Metadata

Metadata backups and archives are automatically created on every volume group and logical volume configuration change unless disabled in the `lvm.conf` file. By default, the metadata backup is stored in the `/etc/lvm/backup` file and the metadata archives are stored in the `/etc/lvm/archives` file. You can manually back up the metadata to the `/etc/lvm/backup`file with the `vgcfgbackup` command.

The `vgcfrestore` command restores the metadata of a volume group from the archive to all the physical volumes in the volume groups.

Renaming a Volume Group

Use the vgrename command to rename an existing volume group.

Either of the following commands renames the existing volume group vg02 to my_volume_group

# vgrename /dev/vg02 /dev/my_volume_group

# vgrename vg02 my_volume_group

Moving a Volume Group to Another System

You can move an entire LVM volume group to another system. It is recommended that you use thevgexport and vgimport commands when you do this.

The vgexport command makes an inactive volume group inaccessible to the system, which allows you to detach its physical volumes. The vgimport command makes a volume group accessible to a machine again after the vgexport command has made it inactive.

To move a volume group form one system to another, perform the following steps:

Make sure that no users are accessing files on the active volumes in the volume group, then unmount the logical volumes.
Use the -a n argument of the vgchange command to mark the volume group as inactive, which prevents any further activity on the volume group.
Use the vgexport command to export the volume group. This prevents it from being accessed by the system from which you are removing it.

After you export the volume group, the physical volume will show up as being in an exported volume group when you execute the pvscan command, as in the following example.
```
# pvscan
  PV /dev/sda1    is in exported VG myvg [17.15 GB / 7.15 GB free]
  PV /dev/sdc1    is in exported VG myvg [17.15 GB / 15.15 GB free]
  PV /dev/sdd1   is in exported VG myvg [17.15 GB / 15.15 GB free]
  ...
```
When the system is next shut down, you can unplug the disks that constitute the volume group and connect them to the new system.
When the disks are plugged into the new system, use the vgimport command to import the volume group, making it accessible to the new system.
Activate the volume group with the -a y argument of the vgchange command.
Mount the file system to make it available for use.

Recreating a Volume Group Directory

To recreate a volume group directory and logical volume special files, use the `vgmknodes`command. This command checks the LVM2 special files in the `/dev` directory that are needed for active logical volumes. It creates any special files that are missing removes unused ones.

You can incorporate the `vgmknodes` command into the `vgscan` command by specifying the `mknodes` argument to the `vgscan` command.

Logical Volume Administration

Creating Logical Volumes

To create a logical volume, use the lvcreate command. You can create linear volumes, striped volumes, and mirrored volumes, as described in the following subsections.

If you do not specify a name for the logical volume, the default name lvol# is used where # is the internal number of the logical volume.

Creating Linear Volumes

When you create a logical volume, the logical volume is carved from a volume group using the free extents on the physical volumes that make up the volume group. Normally logical volumes use up any space available on the underlying physical volumes on a next-free basis. Modifying the logical volume frees and reallocates space in the physical volumes.

The following command creates a logical volume 10 gigabytes in size in the volume group vg1.

# lvcreate -L 10G vg1

The following command creates a 1500 MB linear logical volume named testlv in the volume group testvg, creating the block device /dev/testvg/testlv.

# lvcreate -L1500 -n testlv testvg

The following command creates a 50 gigabyte logical volume named gfslv from the free extents in volume group vg0.

# lvcreate -L 50G -n gfslv vg0

You can use the -l argument of the lvcreate command to specify the size of the logical volume in extents. You can also use this argument to specify the percentage of the volume group to use for the logical volume. The following command creates a logical volume called mylv that uses 60% of the total space in volume group testvg.

# lvcreate -l 60%VG -n mylv testvg

You can also use the -l argument of the lvcreate command to specify the percentage of the remaining free space in a volume group as the size of the logical volume. The following command creates a logical volume called yourlv that uses all of the unallocated space in the volume group testvg.

# lvcreate -l 100%FREE -n yourlv testvg

You can use -l argument of the lvcreate command to create a logical volume that uses the entire volume group. Another way to create a logical volume that uses the entire volume group is to use the vgdisplay command to find the "Total PE" size and to use those results as input to the lvcreate command.

The following commands create a logical volume called mylv that fills the volume group named testvg.

# vgdisplay testvg | grep "Total PE"
Total PE              10230
# lvcreate -l 10230 testvg -n mylv

To create a logical volume to be allocated from a specific physical volume in the volume group, specify the physical volume or volumes at the end at the lvcreate command line. The following command creates a logical volume named testlv in volume group testvg allocated from the physical volume /dev/sdg1,

# lvcreate -L 1500 -ntestlv testvg /dev/sdg1

You can specify which extents of a physical volume are to be used for a logical volume. The following example creates a linear logical volume out of extents 0 through 24 of physical volume /dev/sda1 and extents 50 through 124 of physical volume /dev/sdb1 in volume group testvg.

# lvcreate -l 100 -n testlv testvg /dev/sda1:0-24 /dev/sdb1:50-124

The following example creates a linear logical volume out of extents 0 through 24 of physical volume /dev/sda1 and then continues laying out the logical volume at extent 100.

# lvcreate -l 100 -n testlv testvg /dev/sda1:0-24:100-

The default policy for how the extents of a logical volume are allocated is inherit, which applies the same policy as for the volume group. These policies can be changed using the lvchange command.

Creating Striped Volumes

For large sequential reads and writes, creating a striped logical volume can improve the efficiency of the data I/O.

When you create a striped logical volume, you specify the number of stripes with the -iargument of the lvcreate command. This determines over how many physical volumes the logical volume will be striped. The number of stripes cannot be greater than the number of physical volumes in the volume group (unless the --alloc anywhere argument is used).

If the underlying physical devices that make up a striped logical volume are different sizes, the maximum size of the striped volume is determined by the smallest underlying device. For example, in a two-legged stripe, the maximum size is twice the size of the smaller device. In a three-legged stripe, the maximum size is three times the size of the smallest device.

The following command creates a striped logical volume across 2 physical volumes with a stripe of 64kB. The logical volume is 50 gigabytes in size, is named gfslv, and is carved out of volume group vg0.

# lvcreate -L 50G -i2 -I64 -n gfslv vg0

As with linear volumes, you can specify the extents of the physical volume that you are using for the stripe. The following command creates a striped volume 100 extents in size that stripes across two physical volumes, is named stripelv and is in volume group testvg. The stripe will use sectors 0-49 of /dev/sda1 and sectors 50-99 of /dev/sdb1.

# lvcreate -l 100 -i2 -nstripelv testvg /dev/sda1:0-49 /dev/sdb1:50-99
  Using default stripesize 64.00 KB
  Logical volume "stripelv" created

Creating Mirrored Volumes

When you create a mirrored volume, you specify the number of copies of the data to make with the -m argument of the lvcreate command. Specifying -m1 creates one mirror, which yields two copies of the file system: a linear logical volume plus one copy. Similarly, specifying -m2creates two mirrors, yielding three copies of the file system.

The following command creates a mirrored logical volume with a single mirror. The volume is 50 gigabytes in size, is named mirrorlv, and is carved out of volume group vg0:

# lvcreate -L 50G -m1 -n mirrorlv vg0

An LVM mirror divides the device being copied into regions that, by default, are 512KB in size. You can use the -R argument of the lvcreate command to specify the region size in megabytes. You can also change the default region size by editing the mirror_region_sizesetting in the lvm.conf file.

When a mirror is created, the mirror regions are synchronized. For large mirror components, the sync process may take a long time. When you are creating a new mirror that does not need to be revived, you can specify the --nosync argument to indicate that an initial synchronization from the first device is not required.

LVM maintains a small log which it uses to keep track of which regions are in sync with the mirror or mirrors. By default, this log is kept on disk, which keeps it persistent across reboots. You can specify instead that this log be kept in memory with the --corelog argument; this eliminates the need for an extra log device, but it requires that the entire mirror be resynchronized at every reboot.

The following command creates a mirrored logical volume from the volume group bigvg. The logical is named ondiskmirvol and has a single mirror. The volume is 12 MB in size and keeps the mirror log in memory.

# lvcreate -L 12MB -m1 --corelog -n ondiskmirvol bigvg
  Logical volume "ondiskmirvol" created

The mirror log is created on a separate device from the devices on which any of the mirror legs are created. It is possible, however, to create the mirror log on the same device as one of the mirror legs by using the --alloc anywhere argument of the vgcreate command. This may degrade performance, but it allows you to create a mirror even if you have only two underlying devices.

The following command creates a mirrored logical volume with a single mirror for which the mirror log is on the same device as one of the mirror legs. In this example, the volume group vg0 consists of only two devices. This command creates a 500 MB volume named mirrorlv in the vg0 volume group.

# lvcreate -L 500M -m1 -n mirrorlv -alloc anywhere vg0

Mirroring the Mirror Log

To create a mirror log that is itself mirrored, you can specify the --mirrorlog mirroredargument. The following command creates a mirrored logical volume from the volume group bigvg. The logical volume is named twologvol and has a single mirror. The volume is 12 MB in size and the mirror log is mirrored, with each log kept on a separate device.

# lvcreate -L 12MB -m1 --mirrorlog mirrored -n twologvol bigvg
  Logical volume "twologvol" created

Just as with a standard mirror log, it is possible to create the redundant mirror logs on the same device as the mirror legs by using the --alloc anywhere argument of the vgcreatecommand. This may degrade performance, but it allows you to create a redundant mirror log even if you do not have sufficient underlying devices for each log to be kept on a separate device than the mirror legs.

Specifying Devices for Mirror Components

You can specify which devices to use for the mirror legs and log, and which extents of the devices to use. To force the log onto a particular disk, specify exactly one extent on the disk on which it will be placed. LVM does not necessary respect the order in which devices are listed in the command line. If any physical volumes are listed that is the only space on which allocation will take place. Any physical extents included in the list that are already allocated will get ignored.

# lvcreate -L 500M -m1 -n mirrorlv vg0 /dev/sda1 /dev/sdb1 /dev/sdc1

The following command creates a mirrored logical volume with a single mirror. The volume is 500 MB in size, it is named mirrorlv, and it is carved out of volume group vg0. The first leg of the mirror is on extents 0 through 499 of device /dev/sda1, the second leg of the mirror is on extents 0 through 499 of device /dev/sdb1, and the mirror log starts on extent 0 of device /dev/sdc1. These are 1 MB extents. If any of the specified extents have already been allocated, they will be ignored.

# lvcreate -L 500M -m1 -n mirrorlv vg0 /dev/sda1:0-499 /dev/sdb1:0-499 /dev/sdc1:0

Splitting Off a Redundant Image of a Mirrored Logical Volume

You can split off a redundant image of a mirrored logical volume to form a new logical volume. To split off an image, you use the --splitmirrors argument of the lvconvert command, specifying the number of redundant images to split off. You must use the --name argument of the command to specify a name for the newly-split-off logical volume.

The following command splits off a new logical volume named copy from the mirrored logical volume vg/lv. The new logical volume contains two mirror legs. In this example, LVM selects which devices to split off.

# lvconvert --splitmirrors 2 --name copy vg/lv

You can specify which devices to split off. The following command splits off a new logical volume named copy from the mirrored logical volume vg/lv. The new logical volume contains two mirror legs consisting of devices /dev/sdc1 and /dev/sde1.

# lvconvert --splitmirrors 2 --name copy vg/lv /dev/sd[ce]1

Splitting Off a Redundant Image of a Mirrored Logical Volume

# lvconvert --splitmirrors 2 --name copy vg/lv

# lvconvert --splitmirrors 2 --name copy vg/lv /dev/sd[ce]1

The following command converts the linear logical volume vg00/lvol1 to a mirrored logical volume.

# lvconvert -m1 vg00/lvol1

The following command converts the mirrored logical volume vg00/lvol1 to a linear logical volume, removing the mirror leg.

# lvconvert -m0 vg00/lvol1

Persistent Device Numbers

Major and minor device numbers are allocated dynamically at module load. Some applications work best if the block device always is activated with the same device (major and minor) number. You can specify these with the lvcreate and the lvchange commands by using the following arguments:

--persistent y --major major --minor minor

Use a large minor number to be sure that it has not already been allocated to another device dynamically.

Resizing Logical Volumes

To reduce the size of a logical volume, use the lvreduce command. If the logical volume contains a file system, be sure to reduce the file system first (or use the LVM GUI) so that the logical volume is always at least as large as the file system expects it to be.

The following command reduces the size of logical volume lvol1 in volume group vg00 by 3 logical extents.

# lvreduce -l -3 vg00/lvol1

Changing the Parameters of a Logical Volume Group

To change the parameters of a logical volume, use the lvchange command. For a listing of the parameters you can change, see the lvchange(8) man page.

You can use the lvchange command to activate and deactivate logical volumes. To activate and deactivate all the logical volumes in a volume group at the same time, use the vgchangecommand

The following command changes the permission on volume lvol1 in volume group vg00 to be read-only.

# lvchange -pr vg00/lvol1

Renaming Logical Volumes

To rename an existing logical volume, use the lvrename command.

Either of the following commands renames logical volume lvold in volume group vg02 to lvnew.

# lvrename /dev/vg02/lvold /dev/vg02/lvnew

# lvrename vg02 lvold lvnew

Removing Logical Volumes

To remove an inactive logical volume, use the lvremove command. If the logical volume is currently mounted, unmount the volume before removing it. In addition, in a clustered environment you must deactivate a logical volume before it can be removed.

The following command removes the logical volume /dev/testvg/testlv. from the volume group testvg. Note that in this case the logical volume has not been deactivated.

# lvremove /dev/testvg/testlv
Do you really want to remove active logical volume "testlv"? [y/n]: y
  Logical volume "testlv" successfully removed

You could explicitly deactivate the logical volume before removing it with the lvchange -an command, in which case you would not see the prompt verifying whether you want to remove an active logical volume.

Displaying Logical Volumes

There are three commands you can use to display properties of LVM logical volumes: lvs, lvdisplay, and lvscan.

The lvs command provides logical volume information in a configurable form, displaying one line per logical volume. The lvs command provides a great deal of format control, and is useful for scripting.

The lvdisplay command displays logical volume properties (such as size, layout, and mapping) in a fixed format.

The following command shows the attributes of lvol2 in vg00. If snapshot logical volumes have been created for this original logical volume, this command shows a list of all snapshot logical volumes and their status (active or inactive) as well.

# lvdisplay -v /dev/vg00/lvol2

The lvscan command scans for all logical volumes in the system and lists them, as in the following example.

# lvscan
 ACTIVE                   '/dev/vg0/gfslv' [1.46 GB] inherit

rowing Logical Volumes

To increase the size of a logical volume, use the lvextend command.

After extending the logical volume, you will need to increase the size of the associated file system to match.

When you extend the logical volume, you can indicate how much you want to extend the volume, or how large you want it to be after you extend it.

The following command extends the logical volume /dev/myvg/homevol to 12 gigabytes.

# lvextend -L12G /dev/myvg/homevol 
lvextend -- extending logical volume "/dev/myvg/homevol" to 12 GB
lvextend -- doing automatic backup of volume group "myvg"
lvextend -- logical volume "/dev/myvg/homevol" successfully extended

The following command adds another gigabyte to the logical volume /dev/myvg/homevol.

# lvextend -L+1G /dev/myvg/homevol
lvextend -- extending logical volume "/dev/myvg/homevol" to 13 GB
lvextend -- doing automatic backup of volume group "myvg"
lvextend -- logical volume "/dev/myvg/homevol" successfully extended

As with the lvcreate command, you can use the -l argument of the lvextend command to specify the number of extents by which to increase the size of the logical volume. You can also use this argument to specify a percentage of the volume group, or a percentage of the remaining free space in the volume group. The following command extends the logical volume called testlv to fill all of the unallocated space in the volume group myvg.

# lvextend -l +100%FREE /dev/myvg/testlv
  Extending logical volume testlv to 68.59 GB
  Logical volume testlv successfully resized

After you have extended the logical volume it is necessary to increase the file system size to match.

By default, most file system resizing tools will increase the size of the file system to be the size of the underlying logical volume so you do not need to worry about specifying the same size for each of the two commands.

xtending a Striped Volume

In order to increase the size of a striped logical volume, there must be enough free space on the underlying physical volumes that make up the volume group to support the stripe. For example, if you have a two-way stripe that that uses up an entire volume group, adding a single physical volume to the volume group will not enable you to extend the stripe. Instead, you must add at least two physical volumes to the volume group.

For example, consider a volume group vg that consists of two underlying physical volumes, as displayed with the following vgs command.

# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     2   0   0 wz--n- 271.31G 271.31G

You can create a stripe using the entire amount of space in the volume group.

# lvcreate -n stripe1 -L 271.31G -i 2 vg
  Using default stripesize 64.00 KB
  Rounding up size to full physical extent 271.31 GB
  Logical volume "stripe1" created
# lvs -a -o +devices
  LV      VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe1 vg   -wi-a- 271.31G                               /dev/sda1(0),/dev/sdb1(0)

Note that the volume group now has no more free space.

# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     2   1   0 wz--n- 271.31G    0

The following command adds another physical volume to the volume group, which then has 135G of additional space.

# vgextend vg /dev/sdc1
  Volume group "vg" successfully extended
# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     3   1   0 wz--n- 406.97G 135.66G

At this point you cannot extend the striped logical volume to the full size of the volume group, because two underlying devices are needed in order to stripe the data.

# lvextend vg/stripe1 -L 406G
  Using stripesize of last segment 64.00 KB
  Extending logical volume stripe1 to 406.00 GB
  Insufficient suitable allocatable extents for logical volume stripe1: 34480 
more required

To extend the striped logical volume, add another physical volume and then extend the logical volume. In this example, having added two physical volumes to the volume group we can extend the logical volume to the full size of the volume group.

# vgextend vg /dev/sdd1
  Volume group "vg" successfully extended
# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     4   1   0 wz--n- 542.62G 271.31G
# lvextend vg/stripe1 -L 542G
  Using stripesize of last segment 64.00 KB
  Extending logical volume stripe1 to 542.00 GB
  Logical volume stripe1 successfully resized

If you do not have enough underlying physical devices to extend the striped logical volume, it is possible to extend the volume anyway if it does not matter that the extension is not striped, which may result in uneven performance. When adding space to the logical volume, the default operation is to use the same striping parameters of the last segment of the existing logical volume, but you can override those parameters. The following example extends the existing striped logical volume to use the remaining free space after the initial lvextend command fails.

# lvextend vg/stripe1 -L 406G
  Using stripesize of last segment 64.00 KB
  Extending logical volume stripe1 to 406.00 GB
  Insufficient suitable allocatable extents for logical volume stripe1: 34480 
more required
# lvextend -i1 -l+100%FREE vg/stripe1

Extending a Mirrored Volume

As of the Red Hat Enterprise Linux 5.8 release, it is possible to grow mirrored logical volumes with the lvextend command without performing a synchronization of the new mirror regions.

If you specify the --nosync option when you create a mirrored logical volume with the lvcreate command, the mirror regions are not synchronized when the mirror is created

You can determine whether an existing logical volume was created with the --nosync option by using the lvs command to display the volume's attributes. A logical volume will have an attribute of "M" if it is a mirrored volume that was created without an initial synchronization, and it will have an attribute of "m" if it was created with initial synchronization.

The following command displays the attributes of a mirrored logical volume named lv that was created without initial synchronization.

# lvs vg
  LV   VG   Attr     LSize Pool Origin Snap%  Move Log     Copy%  Convert
  lv   vg   Mwi-a-m- 5.00g                         lv_mlog 100.00

If you grow this mirrored logical volume with the lvextend command, the mirror extension will not be resynchronized.

If you created a mirrored logical volume without specifying the --nosync option of the lvcreate command, you can grow the logical volume without resynchronizing the mirror by specifying the --nosync option of the lvextend command.

The following example extends a logical volume that was created without the --nosync option, indicated that the mirror was synchronized when it was created. This example, however, specifies that the mirror not be synchronized when the volume is extended. Note that the volume has an attribute of "m", but after executing the lvextend commmand with the --nosync option the volume has an attribute of "M".

# lvs vg
  LV   VG   Attr     LSize  Pool Origin Snap%  Move Log     Copy%  Convert
  lv   vg   mwi-a-m- 20.00m                         lv_mlog 100.00        
# lvextend -L +5G vg/lv --nosync
  Extending 2 mirror images.
  Extending logical volume lv to 5.02 GiB
  Logical volume lv successfully resized
# lvs vg
  LV   VG   Attr     LSize Pool Origin Snap%  Move Log     Copy%  Convert
  lv   vg   Mwi-a-m- 5.02g                         lv_mlog 100.00

If a mirror is inactive, it will not automatically skip synchronization when you extend the mirror, even if you create the mirror with the --nosync option specified. Instead, you will be prompted whether to do a full resync of the extended portion of the logical volume.

Extending a Logical Volume with the `cling` Allocation Policy

As of the Red Hat Enterprise Linux 5.7 release, when extending an LVM volume, you can use the --alloc cling option of the lvextend command to specify the cling allocation policy. This policy will choose space on the same physical volumes as the last segment of the existing logical volume. If there is insufficient space on the physical volumes and a list of tags is defined in the lvm.conf file, LVM will check whether any of the tags are attached to the physical volumes and seek to match those physical volume tags between existing extents and new extents.

For example, if you have logical volumes that are mirrored between two sites within a single volume group, you can tag the physical volumes according to where they are situated by tagging the physical volumes with @site1 and @site2 tags and specify the following line in the lvm.conffile:

cling_tag_list = [ "@site1", "@site2" ]

In the following example, the lvm.conf file has been modified to contain the following line:

cling_tag_list = [ "@A", "@B" ]

Also in this example, a volume group taft has been created that consists of the physical volumes /dev/sdb1, /dev/sdc1, /dev/sdd1, /dev/sde1, /dev/sdf1, /dev/sdg1, and /dev/sdh1. These physical volumes have been tagged with tags A, B, and C. The example does not use the C tag, but this will show that LVM uses the tags to select which physical volumes to use for the mirror legs.

# pvs -a -o +pv_tags /dev/sd[bcdefgh]1
  PV         VG   Fmt  Attr PSize   PFree   PV Tags
  /dev/sdb1  taft lvm2 a-   135.66g 135.66g A
  /dev/sdc1  taft lvm2 a-   135.66g 135.66g B
  /dev/sdd1  taft lvm2 a-   135.66g 135.66g B
  /dev/sde1  taft lvm2 a-   135.66g 135.66g C
  /dev/sdf1  taft lvm2 a-   135.66g 135.66g C
  /dev/sdg1  taft lvm2 a-   135.66g 135.66g A
  /dev/sdh1  taft lvm2 a-   135.66g 135.66g A

The following command creates a 100G mirrored volume from the volume group taft.

# lvcreate -m 1 -n mirror --nosync -L 100G taft

The following command shows which devices are used for the mirror legs and mirror log.

# lvs -a -o +devices
  LV                VG        Attr   LSize   Log         Copy%  Devices
  mirror            taft      Mwi-a- 100.00g mirror_mlog 100.00
mirror_mimage_0(0),mirror_mimage_1(0)
  [mirror_mimage_0] taft      iwi-ao 100.00g                    /dev/sdb1(0)
  [mirror_mimage_1] taft      iwi-ao 100.00g                    /dev/sdc1(0)
  [mirror_mlog]     taft      lwi-ao   4.00m                    /dev/sdh1(0)

The following command extends the size of the mirrored volume, using the cling allocation policy to indicate that the mirror legs should be extended using physical volumes with the same tag.

# lvextend --alloc cling -L +100G taft/mirror
  Extending 2 mirror images.
  Extending logical volume mirror to 200.00 GiB
  Logical volume mirror successfully resized

The following display command shows that the mirror legs have been extended using physical volumes with the same tag as the leg. Note that the physical volumes with a tag of C were ignored.

# lvs -a -o +devices
  LV                VG        Attr   LSize   Log         Copy%  Devices
  mirror            taft      Mwi-a- 200.00g mirror_mlog  50.16
mirror_mimage_0(0),mirror_mimage_1(0)
  [mirror_mimage_0] taft      Iwi-ao 200.00g                    /dev/sdb1(0)
  [mirror_mimage_0] taft      Iwi-ao 200.00g                    /dev/sdg1(0)
  [mirror_mimage_1] taft      Iwi-ao 200.00g                    /dev/sdc1(0)
  [mirror_mimage_1] taft      Iwi-ao 200.00g                    /dev/sdd1(0)
  [mirror_mlog]     taft      lwi-ao   4.00m                    /dev/sdh1(0)

Shrinking Logical Volumes

To reduce the size of a logical volume, first unmount the file system. You can then use the lvreduce command to shrink the volume. After shrinking the volume, remount the file system.

Shrinking a logical volume frees some of the volume group to be allocated to other logical volumes in the volume group.

The following example reduces the size of logical volume lvol1 in volume group vg00 by 3 logical extents.

# lvreduce -l -3 vg00/lvol1

Creating Snapshot Volumes

Use the -s argument of the lvcreate command to create a snapshot volume. A snapshot volume is writable.

The following command creates a snapshot logical volume that is 100 MB in size named /dev/vg00/snap. This creates a snapshot of the origin logical volume named /dev/vg00/lvol1. 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 file system to run a backup while the original file system continues to get updated.

# lvcreate --size 100M --snapshot --name snap /dev/vg00/lvol1

After you create a snapshot logical volume, specifying the origin volume on the lvdisplaycommand yields output that includes a list of all snapshot logical volumes and their status (active or inactive).

The following example shows the status of the logical volume /dev/new_vg/lvol0, for which a snapshot volume /dev/new_vg/newvgsnap has been created.

# lvdisplay /dev/new_vg/lvol0
  --- Logical volume ---
  LV Name                /dev/new_vg/lvol0
  VG Name                new_vg
  LV UUID                LBy1Tz-sr23-OjsI-LT03-nHLC-y8XW-EhCl78
  LV Write Access        read/write
  LV snapshot status     source of
                         /dev/new_vg/newvgsnap1 [active]
  LV Status              available
  # open                 0
  LV Size                52.00 MB
  Current LE             13
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2

The lvs command, by default, displays the origin volume and the current percentage of the snapshot volume being used for each snapshot volume. The following example shows the default output for the lvs command for a system that includes the logical volume /dev/new_vg/lvol0, for which a snapshot volume /dev/new_vg/newvgsnap has been created.

# lvs
  LV         VG     Attr   LSize  Origin Snap%  Move Log Copy%
  lvol0      new_vg owi-a- 52.00M
  newvgsnap1 new_vg swi-a-  8.00M lvol0    0.20

Controlling LVM Device Scans with Filters

At startup, the vgscan command is run to scan the block devices on the system looking for LVM labels, to determine which of them are physical volumes and to read the metadata and build up a list of volume groups. The names of the physical volumes are stored in the cache file of each node in the system, /etc/lvm/.cache. Subsequent commands may read that file to avoiding rescanning.

You can control which devices LVM scans by setting up filters in the lvm.conf configuration file. The filters in the lvm.conf file consist of a series of simple regular expressions that get applied to the device names that are in the /dev directory to decide whether to accept or reject each block device found.

The following examples show the use of filters to control which devices LVM scans. Note that some of these examples do not necessarily represent best practice, as the regular expressions are matched freely against the complete pathname. For example, a/loop/ is equivalent to a/.*loop.*/ and would match /dev/solooperation/lvol1.

The following filter adds all discovered devices, which is the default behavior as there is no filter configured in the configuration file:

filter = [ "a/.*/" ]

The following filter removes the cdrom device in order to avoid delays if the drive contains no media:

filter = [ "r|/dev/cdrom|" ]

The following filter adds all loop and removes all other block devices:

filter = [ "a/loop.*/", "r/.*/" ]

The following filter adds all loop and IDE and removes all other block devices:

filter =[ "a|loop.*|", "a|/dev/hd.*|", "r|.*|" ]

The following filter adds just partition 8 on the first IDE drive and removes all other block devices:

filter = [ "a|^/dev/hda8$|", "r/.*/" ]

Online Data Relocation

You can move data while the system is in use with the pvmove command.

The pvmove command breaks up the data to be moved into sections and creates a temporary mirror to move each section.

The following command moves all allocated space off the physical volume /dev/sdc1 to other free physical volumes in the volume group:

# pvmove /dev/sdc1

The following command moves just the extents of the logical volume MyLV.

# pvmove -n MyLV /dev/sdc1

Since the pvmove command can take a long time to execute, you may want to run the command in the background to avoid display of progress updates in the foreground. The following command moves all extents allocated to the physical volume /dev/sdc1 over to /dev/sdf1 in the background.

# pvmove -b /dev/sdc1 /dev/sdf1

The following command reports the progress of the move as a percentage at five second intervals.

# pvmove -i5 /dev/sdd1

Activating Logical Volumes on Individual Nodes in a Cluster

If you have LVM installed in a cluster environment, you may at times need to activate logical volumes exclusively on one node.

To activate logical volumes exclusively on one node, use the lvchange -aey command. Alternatively, you can use lvchange -aly command to activate logical volumes only on the local node but not exclusively. You can later activate them on additional nodes concurrently.

Customized Reporting for LVM

You can produce concise and customizable reports of LVM objects with the pvs, lvs, and vgscommands. The reports that these commands generate include one line of output for each object. Each line contains an ordered list of fields of properties related to the object. There are five ways to select the objects to be reported: by physical volume, volume group, logical volume, physical volume segment, and logical volume segment.

The following sections provide:

A summary of command arguments you can use to control the format of the generated report.
A list of the fields you can select for each LVM object.
A summary of command arguments you can use to sort the generated report.
Instructions for specifying the units of the report output.

ormat Control

Whether you use the pvs, lvs, or vgs command determines the default set of fields displayed and the sort order. You can control the output of these commands with the following arguments:

You can change what fields are displayed to something other than the default by using the-o argument. For example, the following output is the default display for the pvscommand (which displays information about physcial volumes).
```
# pvs
  PV         VG     Fmt  Attr PSize  PFree
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G
```
The following command displays only the physical volume name and size.
```
# pvs -o pv_name,pv_size
  PV         PSize
  /dev/sdb1  17.14G
  /dev/sdc1  17.14G
  /dev/sdd1  17.14G
```

You can append a field to the output with the plus sign (+), which is used in combination with the -o argument.

The following example displays the UUID of the physical volume in addition to the default fields.

# pvs -o +pv_uuid
  PV         VG     Fmt  Attr PSize  PFree  PV UUID
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G onFF2w-1fLC-ughJ-D9eB-M7iv-6XqA-dqGeXY
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G Joqlch-yWSj-kuEn-IdwM-01S9-X08M-mcpsVe
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G yvfvZK-Cf31-j75k-dECm-0RZ3-0dGW-UqkCS

Adding the -v argument to a command includes some extra fields. For example, the pvs -v command will display the DevSize and PV UUID fields in addition to the default fields.

# pvs -v
    Scanning for physical volume names
  PV         VG     Fmt  Attr PSize  PFree  DevSize PV UUID
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G  17.14G onFF2w-1fLC-ughJ-D9eB-M7iv-6XqA-dqGeXY
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G  17.14G Joqlch-yWSj-kuEn-IdwM-01S9-XO8M-mcpsVe
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G  17.14G yvfvZK-Cf31-j75k-dECm-0RZ3-0dGW-tUqkCS

The --noheadings argument suppresses the headings line. This can be useful for writing scripts.

The following example uses the --noheadings argument in combination with the pv_name argument, which will generate a list of all physical volumes.
```
# pvs --noheadings -o pv_name
  /dev/sdb1
  /dev/sdc1
  /dev/sdd1
```

The --separator separator argument uses separator to separate each field.

The following example separates the default output fields of the pvs command with an equals sign (=).

# pvs --separator =
  PV=VG=Fmt=Attr=PSize=PFree
  /dev/sdb1=new_vg=lvm2=a-=17.14G=17.14G
  /dev/sdc1=new_vg=lvm2=a-=17.14G=17.09G
  /dev/sdd1=new_vg=lvm2=a-=17.14G=17.14G

To keep the fields aligned when using the separator argument, use the separatorargument in conjunction with the --aligned argument.

# pvs --separator = --aligned
  PV        =VG    =Fmt =Attr=PSize =PFree
  /dev/sdb1 =new_vg=lvm2=a-  =17.14G=17.14G
  /dev/sdc1 =new_vg=lvm2=a-  =17.14G=17.09G
  /dev/sdd1 =new_vg=lvm2=a-  =17.14G=17.14G

You can use the -P argument of the lvs or vgs command to display information about a failed volume that would otherwise not appear in the output.

Creating an LVM Logical Volume on Three Disks

This example creates an LVM logical volume called new_logical_volume that consists of the disks at /dev/sda1, /dev/sdb1, and /dev/sdc1.

Creating the Physical Volumes

To use disks in a volume group, you label them as LVM physical volumes.

# pvcreate /dev/sda1 /dev/sdb1 /dev/sdc1
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdc1" successfully created

Creating the Volume Group

The following command creates the volume group new_vol_group.

# vgcreate new_vol_group /dev/sda1 /dev/sdb1 /dev/sdc1
  Volume group "new_vol_group" successfully created

You can use the vgs command to display the attributes of the new volume group.

# vgs
  VG            #PV #LV #SN Attr   VSize  VFree
  new_vol_group   3   0   0 wz--n- 51.45G 51.45G

Creating the Logical Volume

The following command creates the logical volume new_logical_volume from the volume group new_vol_group. This example creates a logical volume that uses 2GB of the volume group.

# lvcreate -L2G -n new_logical_volume new_vol_group
  Logical volume "new_logical_volume" created

Creating the File System

The following command creates a GFS file system on the logical volume.

# gfs_mkfs -plock_nolock -j 1 /dev/new_vol_group/new_logical_volume
This will destroy any data on /dev/new_vol_group/new_logical_volume.

Are you sure you want to proceed? [y/n] y

Device:                    /dev/new_vol_group/new_logical_volume
Blocksize:                 4096
Filesystem Size:           491460
Journals:                  1
Resource Groups:           8
Locking Protocol:          lock_nolock
Lock Table:

Syncing...
All Done

The following commands mount the logical volume and report the file system disk space usage.

# mount /dev/new_vol_group/new_logical_volume /mnt
# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/new_vol_group/new_logical_volume
                       1965840        20   1965820   1% /mnt

Creating a Striped Logical Volume

This example creates an LVM striped logical volume called striped_logical_volume that stripes data across the disks at /dev/sda1, /dev/sdb1, and /dev/sdc1.

# pvcreate /dev/sda1 /dev/sdb1 /dev/sdc1
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdc1" successfully created

Creating the Volume Group

The following command creates the volume group volgroup01.

# vgcreate volgroup01 /dev/sda1 /dev/sdb1 /dev/sdc1
  Volume group "volgroup01" successfully created

You can use the vgs command to display the attributes of the new volume group.

# vgs
  VG                #PV #LV #SN Attr   VSize  VFree
  volgroup01          3   0   0 wz--n- 51.45G 51.45G

Creating the Logical Volume

The following command creates the striped logical volume striped_logical_volume from the volume group volgroup01. This example creates a logical volume that is 2 gigabytes in size, with three stripes and a stripe size of 4 kilobytes.

# lvcreate -i3 -I4 -L2G -nstriped_logical_volume volgroup01
  Rounding size (512 extents) up to stripe boundary size (513 extents)
  Logical volume "striped_logical_volume" created

Creating the File System

The following command creates a GFS file system on the logical volume.

#  gfs_mkfs -plock_nolock -j 1 /dev/volgroup01/striped_logical_volume
This will destroy any data on /dev/volgroup01/striped_logical_volume.

Are you sure you want to proceed? [y/n] y

Device:                    /dev/volgroup01/striped_logical_volume
Blocksize:                 4096
Filesystem Size:           492484
Journals:                  1
Resource Groups:           8
Locking Protocol:          lock_nolock
Lock Table:

Syncing...
All Done

The following commands mount the logical volume and report the file system disk space usage.

# mount /dev/volgroup01/striped_logical_volume /mnt
# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      13902624   1656776  11528232  13% /
/dev/hda1               101086     10787     85080  12% /boot
tmpfs                   127880         0    127880   0% /dev/shm
/dev/volgroup01/striped_logical_volume
                       1969936        20   1969916   1% /mnt

Removing a Disk from a Logical Volume

This example shows how you can remove a disk from an existing logical volume, either to replace the disk or to use the disk as part of a different volume. In order to remove a disk, you must first move the extents on the LVM physical volume to a different disk or set of disks.

Moving Extents to Existing Physical Volumes

In this example, the logical volume is distributed across four physical volumes in the volume group myvg.

# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G 15.00G

We want to move the extents off of /dev/sdb1 so that we can remove it from the volume group.

If there are enough free extents on the other physical volumes in the volume group, you can execute the pvmove command on the device you want to remove with no other options and the extents will be distributed to the other devices.

# pvmove /dev/sdb1
  /dev/sdb1: Moved: 2.0%
 ...
  /dev/sdb1: Moved: 79.2%
 ...
  /dev/sdb1: Moved: 100.0%

After the pvmove command has finished executing, the distribution of extents is as follows:

# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 17.15G     0
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G 15.00G

Use the vgreduce command to remove the physical volume /dev/sdb1 from the volume group.

# vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg"
# pvs
  PV         VG   Fmt  Attr PSize  PFree
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G
  /dev/sdb1       lvm2 --   17.15G 17.15G
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G

The disk can now be physically removed or allocated to other users.

Moving Extents to a New Disk

In this example, the logical volume is distributed across three physical volumes in the volume group myvg as follows:

# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdc1  myvg lvm2 a-   17.15G 15.15G  2.00G

We want to move the extents of /dev/sdb1 to a new device, /dev/sdd1.

Creating the New Physical Volume

Create a new physical volume from /dev/sdd1.

# pvcreate /dev/sdd1
  Physical volume "/dev/sdd1" successfully created

Adding the New Physical Volume to the Volume Group

Add /dev/sdd1 to the existing volume group myvg.

# vgextend myvg /dev/sdd1
  Volume group "myvg" successfully extended
# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1   myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdc1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdd1   myvg lvm2 a-   17.15G 17.15G     0

Moving the Data

Use the pvmove command to move the data from /dev/sdb1 to /dev/sdd1.

# pvmove /dev/sdb1 /dev/sdd1
  /dev/sdb1: Moved: 10.0%
...
  /dev/sdb1: Moved: 79.7%
...
  /dev/sdb1: Moved: 100.0%

# pvs -o+pv_used
  PV          VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1   myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1   myvg lvm2 a-   17.15G 17.15G     0
  /dev/sdc1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdd1   myvg lvm2 a-   17.15G 15.15G  2.00G

Removing the Old Physical Volume from the Volume Group

After you have moved the data off /dev/sdb1, you can remove it from the volume group.

# vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg"

You can now reallocate the disk to another volume group or remove the disk from the system.

Displaying Information on Failed Devices

You can use the -P argument of the lvs or vgs command to display information about a failed volume that would otherwise not appear in the output. This argument permits some operations even though the metatdata is not completely consistent internally. For example, if one of the devices that made up the volume group vg failed, the vgs command might show the following output.

# vgs -o +devices
  Volume group "vg" not found

If you specify the -P argument of the vgs command, the volume group is still unusable but you can see more information about the failed device.

 vgs -P -o +devices
  Partial mode. Incomplete volume groups will be activated read-only.
  VG   #PV #LV #SN Attr   VSize VFree Devices
  vg     9   2   0 rz-pn- 2.11T 2.07T unknown device(0)
  vg     9   2   0 rz-pn- 2.11T 2.07T unknown device(5120),/dev/sda1(0)

In this example, the failed device caused both a linear and a striped logical volume in the volume group to fail. The lvs command without the -P argument shows the following output.

# lvs -a -o +devices
  Volume group "vg" not found

Using the -P argument shows the logical volumes that have failed.

# lvs -P -a -o +devices
  Partial mode. Incomplete volume groups will be activated read-only.
  LV     VG   Attr   LSize  Origin Snap%  Move Log Copy%  Devices
  linear vg   -wi-a- 20.00G                               unknown device(0)
  stripe vg   -wi-a- 20.00G                               unknown device(5120),/dev/sda1(0)

The following examples show the output of the pvs and lvs commands with the -P argument specified when a leg of a mirrored logical volume has failed.

#  vgs -a -o +devices -P
  Partial mode. Incomplete volume groups will be activated read-only.
  VG    #PV #LV #SN Attr   VSize VFree Devices
  corey   4   4   0 rz-pnc 1.58T 1.34T my_mirror_mimage_0(0),my_mirror_mimage_1(0)
  corey   4   4   0 rz-pnc 1.58T 1.34T /dev/sdd1(0)
  corey   4   4   0 rz-pnc 1.58T 1.34T unknown device(0)
  corey   4   4   0 rz-pnc 1.58T 1.34T /dev/sdb1(0)

# lvs -a -o +devices -P
  Partial mode. Incomplete volume groups will be activated read-only.
  LV                   VG    Attr   LSize   Origin Snap%  Move Log            Copy%  Devices
  my_mirror            corey mwi-a- 120.00G                    my_mirror_mlog   1.95 my_mirror_mimage_0(0),my_mirror_mimage_1(0)
  [my_mirror_mimage_0] corey iwi-ao 120.00G                                          unknown device(0)
  [my_mirror_mimage_1] corey iwi-ao 120.00G                                          /dev/sdb1(0)
  [my_mirror_mlog]     corey lwi-ao   4.00M                                          /dev/sdd1(0)

Recovering from LVM Mirror Failure

This section provides an example of recovering from a situation where one leg of an LVM mirrored volume fails because the underlying device for a physical volume goes down. When a mirror leg fails, LVM converts the mirrored volume into a linear volume, which continues to operate as before but without the mirrored redundancy. At that point, you can add a new disk device to the system to use as a replacement physical device and rebuild the mirror.

The following command creates the physical volumes which will be used for the mirror.

# pvcreate /dev/sd[abcdefgh][12]
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sda2" successfully created
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdb2" successfully created
  Physical volume "/dev/sdc1" successfully created
  Physical volume "/dev/sdc2" successfully created
  Physical volume "/dev/sdd1" successfully created
  Physical volume "/dev/sdd2" successfully created
  Physical volume "/dev/sde1" successfully created
  Physical volume "/dev/sde2" successfully created
  Physical volume "/dev/sdf1" successfully created
  Physical volume "/dev/sdf2" successfully created
  Physical volume "/dev/sdg1" successfully created
  Physical volume "/dev/sdg2" successfully created
  Physical volume "/dev/sdh1" successfully created
  Physical volume "/dev/sdh2" successfully created

The following commands creates the volume group vg and the mirrored volume groupfs.

# vgcreate vg /dev/sd[abcdefgh][12]
  Volume group "vg" successfully created
# lvcreate -L 750M -n groupfs -m 1 vg /dev/sda1 /dev/sdb1 /dev/sdc1
  Rounding up size to full physical extent 752.00 MB
  Logical volume "groupfs" created

You can use the lvs command to verify the layout of the mirrored volume and the underlying devices for the mirror leg and the mirror log. Note that in the first example the mirror is not yet completely synced; you should wait until the Copy% field displays 100.00 before continuing.

# lvs -a -o +devices
  LV                 VG   Attr   LSize   Origin Snap%  Move Log          Copy% Devices
  groupfs            vg   mwi-a- 752.00M                    groupfs_mlog 21.28 groupfs_mimage_0(0),groupfs_mimage_1(0)
  [groupfs_mimage_0] vg   iwi-ao 752.00M                                       /dev/sda1(0)
  [groupfs_mimage_1] vg   iwi-ao 752.00M                                       /dev/sdb1(0)
  [groupfs_mlog]     vg   lwi-ao   4.00M                                       /dev/sdc1(0)

# lvs -a -o +devices
  LV                 VG   Attr   LSize   Origin Snap%  Move Log          Copy%  Devices
  groupfs            vg   mwi-a- 752.00M                    groupfs_mlog 100.00 groupfs_mimage_0(0),groupfs_mimage_1(0)
  [groupfs_mimage_0] vg   iwi-ao 752.00M                                        /dev/sda1(0)
  [groupfs_mimage_1] vg   iwi-ao 752.00M                                        /dev/sdb1(0)
  [groupfs_mlog]     vg   lwi-ao   4.00M     i                                  /dev/sdc1(0)

In this example, the primary leg of the mirror /dev/sda1 fails. Any write activity to the mirrored volume causes LVM to detect the failed mirror. When this occurs, LVM converts the mirror into a single linear volume. In this case, to trigger the conversion, we execute a ddcommand

# dd if=/dev/zero of=/dev/vg/groupfs count=10
10+0 records in
10+0 records out

You can use the lvs command to verify that the device is now a linear device. Because of the failed disk, I/O errors occur.

# lvs -a -o +devices
  /dev/sda1: read failed after 0 of 2048 at 0: Input/output error
  /dev/sda2: read failed after 0 of 2048 at 0: Input/output error
  LV      VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  groupfs vg   -wi-a- 752.00M                               /dev/sdb1(0)

At this point you should still be able to use the logical volume, but there will be no mirror redundancy.

To rebuild the mirrored volume, you replace the broken drive and recreate the physical volume. If you use the same disk rather than replacing it with a new one, you will see "inconsistent" warnings when you run the pvcreate command.

# pvcreate /dev/sda[12]
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sda2" successfully created

# pvscan
  PV /dev/sdb1   VG vg   lvm2 [67.83 GB / 67.10 GB free]
  PV /dev/sdb2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sda1           lvm2 [603.94 GB]
  PV /dev/sda2           lvm2 [603.94 GB]
  Total: 16 [2.11 TB] / in use: 14 [949.65 GB] / in no VG: 2 [1.18 TB]

Next you extend the original volume group with the new physical volume.

# vgextend vg /dev/sda[12]
  Volume group "vg" successfully extended

# pvscan
  PV /dev/sdb1   VG vg   lvm2 [67.83 GB / 67.10 GB free]
  PV /dev/sdb2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sda1   VG vg   lvm2 [603.93 GB / 603.93 GB free]
  PV /dev/sda2   VG vg   lvm2 [603.93 GB / 603.93 GB free]
  Total: 16 [2.11 TB] / in use: 16 [2.11 TB] / in no VG: 0 [0   ]

Convert the linear volume back to its original mirrored state.

# lvconvert -m 1 /dev/vg/groupfs /dev/sda1 /dev/sdb1 /dev/sdc1
  Logical volume mirror converted.

You can use the lvs command to verify that the mirror is restored.

# lvs -a -o +devices
  LV                 VG   Attr   LSize   Origin Snap%  Move Log          Copy% Devices
  groupfs            vg   mwi-a- 752.00M                    groupfs_mlog 68.62 groupfs_mimage_0(0),groupfs_mimage_1(0)
  [groupfs_mimage_0] vg   iwi-ao 752.00M                                       /dev/sdb1(0)
  [groupfs_mimage_1] vg   iwi-ao 752.00M                                       /dev/sda1(0)
  [groupfs_mlog]     vg   lwi-ao   4.00M                                       /dev/sdc1(0)

Recovering Physical Volume Metadata

If the volume group metadata area of a physical volume is accidentally overwritten or otherwise destroyed, you will get an error message indicating that the metadata area is incorrect, or that the system was unable to find a physical volume with a particular UUID. You may be able to recover the data the physical volume by writing a new metadata area on the physical volume specifying the same UUID as the lost metadata.

The following example shows the sort of output you may see if the metadata area is missing or corrupted.

# lvs -a -o +devices
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find all physical volumes for volume group VG.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find all physical volumes for volume group VG.
  ...

You may be able to find the UUID for the physical volume that was overwritten by looking in the /etc/lvm/archive directory. Look in the file VolumeGroupName_xxxx.vg for the last known valid archived LVM metadata for that volume group.

Alternately, you may find that deactivating the volume and setting the partial (-P) argument will enable you to find the UUID of the missing corrupted physical volume.

# vgchange -an --partial
  Partial mode. Incomplete volume groups will be activated read-only.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  ...

Use the --uuid and --restorefile arguments of the pvcreate command to restore the physical volume. The following example labels the /dev/sdh1 device as a physical volume with the UUID indicated above, FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk. This command restores the physical volume label with the metadata information contained in VG_00050.vg, the most recent good archived metatdata for volume group . The restorefile argument instructs the pvcreate command to make the new physical volume compatible with the old one on the volume group, ensuring that the new metadata will not be placed where the old physical volume contained data (which could happen, for example, if the original pvcreate command had used the command line arguments that control metadata placement, or it the physical volume was originally created using a different version of the software that used different defaults). The pvcreate command overwrites only the LVM metadata areas and does not affect the existing data areas.

# pvcreate --uuid "FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk" --restorefile /etc/lvm/archive/VG_00050.vg /dev/sdh1
  Physical volume "/dev/sdh1" successfully created

You can then use the vgcfgrestore command to restore the volume group's metadata.

# vgcfgrestore VG
  Restored volume group VG

You can now display the logical volumes.

# lvs -a -o +devices
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe VG   -wi--- 300.00G                               /dev/sdh1 (0),/dev/sda1(0)
  stripe VG   -wi--- 300.00G                               /dev/sdh1 (34728),/dev/sdb1(0)

The following commands activate the volumes and display the active volumes.

# lvchange -ay /dev/VG/stripe
# lvs -a -o +devices
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe VG   -wi-a- 300.00G                               /dev/sdh1 (0),/dev/sda1(0)
  stripe VG   -wi-a- 300.00G                               /dev/sdh1 (34728),/dev/sdb1(0)

If the on-disk LVM metadata takes as least as much space as what overrode it, this command can recover the physical volume. If what overrode the metadata went past the metadata area, the data on the volume may have been affected. You might be able to use the fsck command to recover that data.

Replacing a Missing Physical Volume

If a physical volume fails or otherwise needs to be replaced, you can label a new physical volume to replace the one that has been lost in the existing volume group by following the same procedure as you would for recovering physical volume metadata. You can use the --partial and --verbose arguments of the vgdisplay command to display the UUIDs and sizes of any physical volumes that are no longer present. If you wish to substitute another physical volume of the same size, you can use the pvcreate command with the --restorefile and --uuid arguments to initialize a new device with the same UUID as the missing physical volume. You can then use the vgcfgrestore command to restore the volume group's metadata.

Removing Lost Physical Volumes from a Volume Group

If you lose a physical volume, you can activate the remaining physical volumes in the volume group with the --partial argument of the vgchange command. You can remove all the logical volumes that used that physical volume from the volume group with the --removemissing argument of the vgreduce command.

It is recommended that you run the vgreduce command with the --test argument to verify what you will be destroying.

Like most LVM operations, the vgreduce command is reversible in a sense if you immediately use the vgcfgrestore command to restore the volume group metadata to its previous state. For example, if you used the --removemissing argument of the vgreduce command without the --test argument and find you have removed logical volumes you wanted to keep, you can still replace the physical volume and use another vgcfgrestore command to return the volume group to its previous state.

The Device Mapper

The Device Mapper is a kernel driver that provides a framework for volume management. It provides a generic way of creating mapped devices, which may be used as logical volumes. It does not specifically know about volume groups or metadata formats.

The Device Mapper provides the foundation for a number of higher-level technologies. In addition to LVM, Device-Mapper multipath and the dmraid command use the Device Mapper. The application interface to the Device Mapper is the ioctl system call. The user interface is the dmsetup command.

LVM logical volumes are activated using the Device Mapper. Each logical volume is translated into a mapped device. Each segment translates into a line in the mapping table that describes the device. The Device Mapper supports a variety of mapping targets, including linear mapping, striped mapping, and error mapping. So, for example, two disks may be concatenated into one logical volume with a pair of linear mappings, one for each disk. When LVM2 creates a volume, it creates an underlying device-mapper device that can be queried with the dmsetup command.

The LVM Configuration Files

LVM supports multiple configuration files. At system startup, the lvm.conf configuration file is loaded from the directory specified by the environment variable LVM_SYSTEM_DIR, which is set to /etc/lvm by default.

The lvm.conf file can specify additional configuration files to load. Settings in later files override settings from earlier ones. To display the settings in use after loading all the configuration files, execute the lvm dumpconfig command.

The LVM Configuration Files

The following files are used for LVM configuration:

/etc/lvm/lvm.conf: Central configuration file read by the tools.
/etc/lvm/lvm_hosttag.conf: For each host tag, an extra configuration file is read if it exists: lvm_hosttag.conf. If that file defines new tags, then further configuration files will be appended to the list of tiles to read in.

In addition to the LVM configuration files, a system running LVM includes the following files that affect LVM system setup:

/etc/lvm/.cache: Device name filter cache file (configurable).
/etc/lvm/backup/: Directory for automatic volume group metadata backups (configurable).
/etc/lvm/archive/: Directory for automatic volume group metadata archives (configurable with regard to directory path and archive history depth).
/var/lock/lvm/: In single-host configuration, lock files to prevent parallel tool runs from corrupting the metadata; in a cluster, cluster-wide DLM is used.

Tuesday, April 8, 2014

Red Hat LVM notes

Setting the Partition Type

Initializing Physical Volumes

Scanning for Block Devices

Displaying Physical Volumes

Preventing Allocation on a Physical Volume

Resizing a Physical Volume

Removing Physical Volumes

If a device is no longer required for use by LVM, you can remove the LVM label with the pvremove command. Executing the pvremove command zeroes the LVM metadata on an empty physical volume.

Volume Group Administration

reating Volume Groups

Creating Volume Groups in a Cluster

Adding Physical Volumes to a Volume Group

Displaying Volume Groups

Scanning Disks for Volume Groups to Build the Cache File

Removing Physical Volumes from a Volume Group

Changing the Parameters of a Volume Group

Activating and Deactivating Volume Groups

Removing Volume Groups

To remove a volume group that contains no logical volumes, use the vgremove command. # vgremove officevg Volume group "officevg" successfully removed

Splitting a Volume Group

Combining Volume Groups

Backing Up Volume Group Metadata

Renaming a Volume Group

Use the vgrename command to rename an existing volume group. Either of the following commands renames the existing volume group vg02 to my_volume_group # vgrename /dev/vg02 /dev/my_volume_group # vgrename vg02 my_volume_group

Moving a Volume Group to Another System

Recreating a Volume Group Directory

Logical Volume Administration

Creating Logical Volumes

Creating Linear Volumes

Creating Striped Volumes

Creating Mirrored Volumes

Mirroring the Mirror Log

Specifying Devices for Mirror Components

Splitting Off a Redundant Image of a Mirrored Logical Volume

Splitting Off a Redundant Image of a Mirrored Logical Volume

Persistent Device Numbers

Resizing Logical Volumes

Changing the Parameters of a Logical Volume Group

Renaming Logical Volumes

Removing Logical Volumes

Displaying Logical Volumes

rowing Logical Volumes

xtending a Striped Volume

Extending a Mirrored Volume

Extending a Logical Volume with the cling Allocation Policy

Shrinking Logical Volumes

Creating Snapshot Volumes

Controlling LVM Device Scans with Filters

Online Data Relocation

Activating Logical Volumes on Individual Nodes in a Cluster

Customized Reporting for LVM

ormat Control

Creating an LVM Logical Volume on Three Disks

Creating the Physical Volumes

To use disks in a volume group, you label them as LVM physical volumes.

Creating the Volume Group

Creating the Logical Volume

Creating the File System

Creating a Striped Logical Volume

Creating the Volume Group

Creating the Logical Volume

Creating the File System

Removing a Disk from a Logical Volume

Moving Extents to Existing Physical Volumes

Moving Extents to a New Disk

Creating the New Physical Volume

Adding the New Physical Volume to the Volume Group

Moving the Data

Removing the Old Physical Volume from the Volume Group

Displaying Information on Failed Devices

Recovering from LVM Mirror Failure

Recovering Physical Volume Metadata

Replacing a Missing Physical Volume

Removing Lost Physical Volumes from a Volume Group

The Device Mapper

The LVM Configuration Files

The LVM Configuration Files

Metadata Contents

If a device is no longer required for use by LVM, you can remove the LVM label with the `pvremove` command. Executing the `pvremove` command zeroes the LVM metadata on an empty physical volume.

To remove a volume group that contains no logical volumes, use the `vgremove` command.

# `vgremove officevg` Volume group "officevg" successfully removed

Use the `vgrename` command to rename an existing volume group.

Either of the following commands renames the existing volume group `vg02` to `my_volume_group`

# vgrename /dev/vg02 /dev/my_volume_group

# `vgrename vg02 my_volume_group`

Extending a Logical Volume with the `cling` Allocation Policy