NAME¶

lvm — LVM2 tools

SYNOPSIS¶

lvm [command|file]

DESCRIPTION¶

lvm provides the command-line tools for LVM2. A separate manual page describes each command in detail.

If lvm is invoked with no arguments it presents a readline prompt (assuming it was compiled with readline support). LVM commands may be entered interactively at this prompt with readline facilities including history and command name and option completion. Refer to readline(3) for details.

If lvm is invoked with argv[0] set to the name of a specific LVM command (for example by using a hard or soft link) it acts as that command.

On invocation, lvm requires that only the standard file descriptors stdin, stdout and stderr are available. If others are found, they get closed and messages are issued warning about the leak. This warning can be suppressed by setting the environment variable LVM_SUPPRESS_FD_WARNINGS.

Where commands take VG or LV names as arguments, the full path name is optional. An LV called "lvol0" in a VG called "vg0" can be specified as "vg0/lvol0". Where a list of VGs is required but is left empty, a list of all VGs will be substituted. Where a list of LVs is required but a VG is given, a list of all the LVs in that VG will be substituted. So lvdisplay vg0 will display all the LVs in "vg0". Tags can also be used - see --addtag below.

One advantage of using the built-in shell is that configuration information gets cached internally between commands.

A file containing a simple script with one command per line can also be given on the command line. The script can also be executed directly if the first line is #! followed by the absolute path of lvm.

BUILT-IN COMMANDS¶

The following commands are built into lvm without links normally being created in the filesystem for them.

config

The same as lvmconfig(8) below.

devtypes

Display the recognised built-in block device types.

dumpconfig

The same as lvmconfig(8) below.

formats

Display recognised metadata formats.

help

Display the help text.

lvpoll

Complete lvmpolld operations (Internal command).

pvdata

Not implemented in LVM2.

segtypes

Display recognised Logical Volume segment types.

systemid

Display any system ID currently set on this host.

tags

Display any tags defined on this host.

version

Display version information.

COMMANDS¶

The following commands implement the core LVM functionality.

pvchange

Change attributes of a Physical Volume.

pvck

Check Physical Volume metadata.

pvcreate

Initialize a disk or partition for use by LVM.

pvdisplay

Display attributes of a Physical Volume.

pvmove

Move Physical Extents.

pvremove

Remove a Physical Volume.

pvresize

Resize a disk or partition in use by LVM2.

pvs

Report information about Physical Volumes.

pvscan

Scan all disks for Physical Volumes.

vgcfgbackup

Backup Volume Group descriptor area.

vgcfgrestore

Restore Volume Group descriptor area.

vgchange

Change attributes of a Volume Group.

vgck

Check Volume Group metadata.

vgconvert

Convert Volume Group metadata format.

vgcreate

Create a Volume Group.

vgdisplay

Display attributes of Volume Groups.

vgexport

Make volume Groups unknown to the system.

vgextend

Add Physical Volumes to a Volume Group.

vgimport

Make exported Volume Groups known to the system.

vgimportclone

Import and rename duplicated Volume Group (e.g. a hardware snapshot).

vgmerge

Merge two Volume Groups.

vgmknodes

Recreate Volume Group directory and Logical Volume special files

vgreduce

Reduce a Volume Group by removing one or more Physical Volumes.

vgremove

Remove a Volume Group.

vgrename

Rename a Volume Group.

vgs

Report information about Volume Groups.

vgscan

Scan all disks for Volume Groups and rebuild caches.

vgsplit

Split a Volume Group into two, moving any logical volumes from one Volume Group to another by moving entire Physical Volumes.

lvchange

Change attributes of a Logical Volume.

lvconvert

Convert a Logical Volume from linear to mirror or snapshot.

lvcreate

Create a Logical Volume in an existing Volume Group.

lvdisplay

Display attributes of a Logical Volume.

lvextend

Extend the size of a Logical Volume.

lvmchange

Change attributes of the Logical Volume Manager.

lvmconfig

Display the configuration information after loading lvm.conf(5) and any other configuration files.

lvmdiskscan

Scan for all devices visible to LVM2.

lvmdump

Create lvm2 information dumps for diagnostic purposes.

lvreduce

Reduce the size of a Logical Volume.

lvremove

Remove a Logical Volume.

lvrename

Rename a Logical Volume.

lvresize

Resize a Logical Volume.

lvs

Report information about Logical Volumes.

lvscan

Scan (all disks) for Logical Volumes.

The following commands are not implemented in LVM2 but might be in the future: lvmsadc, lvmsar, pvdata.

OPTIONS¶

The following options are available for many of the commands. They are implemented generically and documented here rather than repeated on individual manual pages.

Additional hyphens within option names are ignored. For example, --readonly and --read-only are both accepted.

-h|-?|--help
Display the help text.

--version
Display version information.

-v|--verbose
Set verbose level. Repeat from 1 to 3 times to increase the detail of messages sent to stdout and stderr. Overrides config file setting.

-d|--debug
Set debug level. Repeat from 1 to 6 times to increase the detail of messages sent to the log file and/or syslog (if configured). Overrides config file setting.

-q|--quiet
Suppress output and log messages. Overrides -d and -v. Repeat once to also suppress any prompts with answer 'no'.

--yes
Don't prompt for confirmation interactively but instead always assume the answer is 'yes'. Take great care if you use this!

-t|--test
Run in test mode. Commands will not update metadata. This is implemented by disabling all metadata writing but nevertheless returning success to the calling function. This may lead to unusual error messages in multi-stage operations if a tool relies on reading back metadata it believes has changed but hasn't.

--driverloaded {y|n}
Whether or not the device-mapper kernel driver is loaded. If you set this to n, no attempt will be made to contact the driver.

-A|--autobackup {y|n}
Whether or not to metadata should be backed up automatically after a change. You are strongly advised not to disable this! See vgcfgbackup(8).

-P|--partial
When set, the tools will do their best to provide access to Volume Groups that are only partially available (one or more Physical Volumes belonging to the Volume Group are missing from the system). Where part of a logical volume is missing, /dev/ioerror will be substituted, and you could use dmsetup(8) to set this up to return I/O errors when accessed, or create it as a large block device of nulls. Metadata may not be changed with this option. To insert a replacement Physical Volume of the same or large size use pvcreate -u to set the uuid to match the original followed by vgcfgrestore(8).

-S|--select Selection
For reporting commands, display only rows that match Selection criteria. All rows are displayed with the additional "selected" column (-o selected) showing 1 if the row matches the Selection and 0 otherwise. For non-reporting commands which process LVM entities, the selection can be used to match items to process. See SELECTION CRITERIA section of this man page for more information about the way the selection criteria are constructed.

-M|--metadatatype Type
Specifies which type of on-disk metadata to use, such as lvm1 or lvm2, which can be abbreviated to 1 or 2 respectively. The default (lvm2) can be changed by setting format in the global section of the config file lvm.conf(5).

--ignorelockingfailure
This lets you proceed with read-only metadata operations such as lvchange -ay and vgchange -ay even if the locking module fails. One use for this is in a system init script if the lock directory is mounted read-only when the script runs.

--ignoreskippedcluster
Use to avoid exiting with an non-zero status code if the command is run without clustered locking and some clustered Volume Groups have to be skipped over.

--readonly
Run the command in a special read-only mode which will read on-disk metadata without needing to take any locks. This can be used to peek inside metadata used by a virtual machine image while the virtual machine is running. It can also be used to peek inside the metadata of clustered Volume Groups when clustered locking is not configured or running. No attempt will be made to communicate with the device-mapper kernel driver, so this option is unable to report whether or not Logical Volumes are actually in use.

--foreign
Cause the command to access foreign VGs, that would otherwise be skipped. It can be used to report or display a VG that is owned by another host. This option can cause a command to perform poorly because lvmetad caching is not used and metadata is read from disks.

--shared
Cause the command to access shared VGs, that would otherwise be skipped when lvmlockd is not being used. It can be used to report or display a lockd VG without locking. Applicable only if LVM is compiled with lockd support.

--addtag Tag
Add the tag Tag to a PV, VG or LV. Supply this argument multiple times to add more than one tag at once. A tag is a word that can be used to group LVM2 objects of the same type together. Tags can be given on the command line in place of PV, VG or LV arguments. Tags should be prefixed with @ to avoid ambiguity. Each tag is expanded by replacing it with all objects possessing that tag which are of the type expected by its position on the command line. PVs can only possess tags while they are part of a Volume Group: PV tags are discarded if the PV is removed from the VG. As an example, you could tag some LVs as database and others as userdata and then activate the database ones with lvchange -ay @database. Objects can possess multiple tags simultaneously. Only the new LVM2 metadata format supports tagging: objects using the LVM1 metadata format cannot be tagged because the on-disk format does not support it. Characters allowed in tags are: A-Z a-z 0-9 _ + . - and as of version 2.02.78 the following characters are also accepted: / = ! : # &.

--deltag Tag
Delete the tag Tag from a PV, VG or LV, if it's present. Supply this argument multiple times to remove more than one tag at once.

--alloc {anywhere|contiguous|cling|inherit|normal}
Selects the allocation policy when a command needs to allocate Physical Extents from the Volume Group. Each Volume Group and Logical Volume has an allocation policy defined. The default for a Volume Group is normal which applies common-sense rules such as not placing parallel stripes on the same Physical Volume. The default for a Logical Volume is inherit which applies the same policy as for the Volume Group. These policies can be changed using lvchange(8) and vgchange(8) or overridden on the command line of any command that performs allocation. The contiguous policy requires that new Physical Extents be placed adjacent to existing Physical Extents. The cling policy places new Physical Extents on the same Physical Volume as existing Physical Extents in the same stripe of the Logical Volume. If there are sufficient free Physical Extents to satisfy an allocation request but normal doesn't use them, anywhere will - even if that reduces performance by placing two stripes on the same Physical Volume.

--commandprofile ProfileName
Selects the command configuration profile to use when processing an LVM command. See also lvm.conf(5) for more information about command profile config and the way it fits with other LVM configuration methods. Using --commandprofile option overrides any command profile specified via LVM_COMMAND_PROFILE environment variable.

--metadataprofile ProfileName
Selects the metadata configuration profile to use when processing an LVM command. When using metadata profile during Volume Group or Logical Volume creation, the metadata profile name is saved in metadata. When such Volume Group or Logical Volume is processed next time, the metadata profile is automatically applied and the use of --metadataprofile option is not necessary. See also lvm.conf(5) for more information about metadata profile config and the way it fits with other LVM configuration methods.

--profile ProfileName
A short form of --metadataprofile for vgcreate, lvcreate, vgchange and lvchange command and a short form of --commandprofile for any other command (with the exception of lvmconfig command where the --profile has special meaning, see lvmconfig(8) for more information).

--config ConfigurationString
Uses the ConfigurationString as direct string representation of the configuration to override the existing configuration. The ConfigurationString is of exactly the same format as used in any LVM configuration file. See lvm.conf(5) for more information about direct config override on command line and the way it fits with other LVM configuration methods.

VALID NAMES¶

The valid characters for VG and LV names are: a-z A-Z 0-9 + _ . -

VG and LV names cannot begin with a hyphen. There are also various reserved names that are used internally by lvm that can not be used as LV or VG names. A VG cannot be called anything that exists in /dev/ at the time of creation, nor can it be called '.' or '..'. An LV cannot be called '.', '..', 'snapshot' or 'pvmove'. The LV name may also not contain any of the following strings: '_cdata', '_cmeta', '_corig', '_mlog', '_mimage', '_pmspare', '_rimage', '_rmeta', '_tdata', '_tmeta' or '_vorigin'. A directory bearing the name of each Volume Group is created under /dev when any of its Logical Volumes are activated. Each active Logical Volume is accessible from this directory as a symbolic link leading to a device node. Links or nodes in /dev/mapper are intended only for internal use and the precise format and escaping might change between releases and distributions. Other software and scripts should use the /dev/VolumeGroupName/LogicalVolumeName format to reduce the chance of needing amendment when the software is updated. Should you need to process the node names in /dev/mapper, you may use dmsetup splitname to separate out the original VG, LV and internal layer names.

UNIQUE NAMES¶

VG names should be unique. vgcreate will produce an error if the specified VG name matches an existing VG name. However, there are cases where different VGs with the same name can appear to LVM, e.g. after moving disks or changing filters.

When VGs with the same name exist, commands operating on all VGs will include all of the VGs with the same name. If the ambiguous VG name is specified on the command line, the command will produce an error. The error states that multiple VGs exist with the specified name. To process one of the VGs specifically, the --select option should be used with the UUID of the intended VG: '--select vg_uuid=<uuid>'.

An exception is if all but one of the VGs with the shared name is foreign (see lvmsystemid(7).) In this case, the one VG that is not foreign is assumed to be the intended VG and is processed.

ALLOCATION¶

When an operation needs to allocate Physical Extents for one or more Logical Volumes, the tools proceed as follows:

First of all, they generate the complete set of unallocated Physical Extents in the Volume Group. If any ranges of Physical Extents are supplied at the end of the command line, only unallocated Physical Extents within those ranges on the specified Physical Volumes are considered.

Then they try each allocation policy in turn, starting with the strictest policy (contiguous) and ending with the allocation policy specified using --alloc or set as the default for the particular Logical Volume or Volume Group concerned. For each policy, working from the lowest-numbered Logical Extent of the empty Logical Volume space that needs to be filled, they allocate as much space as possible according to the restrictions imposed by the policy. If more space is needed, they move on to the next policy.

The restrictions are as follows:

Contiguous requires that the physical location of any Logical Extent that is not the first Logical Extent of a Logical Volume is adjacent to the physical location of the Logical Extent immediately preceding it.

Cling requires that the Physical Volume used for any Logical Extent to be added to an existing Logical Volume is already in use by at least one Logical Extent earlier in that Logical Volume. If the configuration parameter allocation/cling_tag_list is defined, then two Physical Volumes are considered to match if any of the listed tags is present on both Physical Volumes. This allows groups of Physical Volumes with similar properties (such as their physical location) to be tagged and treated as equivalent for allocation purposes.

When a Logical Volume is striped or mirrored, the above restrictions are applied independently to each stripe or mirror image (leg) that needs space.

Normal will not choose a Physical Extent that shares the same Physical Volume as a Logical Extent already allocated to a parallel Logical Volume (i.e. a different stripe or mirror image/leg) at the same offset within that parallel Logical Volume.

When allocating a mirror log at the same time as Logical Volumes to hold the mirror data, Normal will first try to select different Physical Volumes for the log and the data. If that's not possible and the allocation/mirror_logs_require_separate_pvs configuration parameter is set to 0, it will then allow the log to share Physical Volume(s) with part of the data.

When allocating thin pool metadata, similar considerations to those of a mirror log in the last paragraph apply based on the value of the allocation/thin_pool_metadata_require_separate_pvs configuration parameter.

If you rely upon any layout behaviour beyond that documented here, be aware that it might change in future versions of the code.

For example, if you supply on the command line two empty Physical Volumes that have an identical number of free Physical Extents available for allocation, the current code considers using each of them in the order they are listed, but there is no guarantee that future releases will maintain that property. If it is important to obtain a specific layout for a particular Logical Volume, then you should build it up through a sequence of lvcreate(8) and lvconvert(8) steps such that the restrictions described above applied to each step leave the tools no discretion over the layout.

To view the way the allocation process currently works in any specific case, read the debug logging output, for example by adding -vvvv to a command.

LOGICAL VOLUME TYPES¶

Some logical volume types are simple to create and can be done with a single lvcreate(8) command. The linear and striped logical volume types are an example of this. Other logical volume types may require more than one command to create. The cache (lvmcache(7)) and thin provisioning (lvmthin(7)) types are examples of this.

SELECTION CRITERIA¶

The selection criteria are a set of statements combined by logical and grouping operators. The statement consists of column name for which a set of valid values is defined using comparison operators. For complete list of column names (fields) that can be used in selection, see the output of <lvm reporting command> -S help.

DIAGNOSTICS¶

All tools return a status code of zero on success or non-zero on failure.

ENVIRONMENT VARIABLES¶

HOME

Directory containing .lvm_history if the internal readline shell is invoked.

LVM_COMMAND_PROFILE

Name of default command profile to use for LVM commands. This profile is overriden by direct use of --commandprofile command line option.

LVM_SYSTEM_DIR

Directory containing lvm.conf(5) and other LVM system files. Defaults to "/etc/lvm".

LVM_SUPPRESS_FD_WARNINGS

Suppress warnings about unexpected file descriptors passed into LVM.

LVM_VG_NAME

The Volume Group name that is assumed for any reference to a Logical Volume that doesn't specify a path. Not set by default.

LVM_LVMETAD_PIDFILE

Path to the file that stores the lvmetad process ID.

LVM_LVMETAD_SOCKET

Path to the socket used to communicate with lvmetad.

LVM_LVMPOLLD_PIDFILE

Path to the file that stores the lvmpolld process ID.

LVM_LVMPOLLD_SOCKET

Path to the socket used to communicate with lvmpolld..

LVM_LOG_FILE_EPOCH

A string of up to 32 letters appended to the log filename and followed by the process ID and a timestamp. When set, each process logs to a separate file.

LVM_EXPECTED_EXIT_STATUS

The status anticipated when the process exits. Use ">N" to match any status greater than N. If the actual exit status matches and a log file got produced, it is deleted. LVM_LOG_FILE_EPOCH and LVM_EXPECTED_EXIT_STATUS together allow automated test scripts to discard uninteresting log data.

LVM_SUPPRESS_LOCKING_FAILURE_MESSAGES

Used to suppress warning messages when the configured locking is known to be unavailable.

DM_ABORT_ON_INTERNAL_ERRORS

Abort processing if the code detects a non-fatal internal error.

DM_DISABLE_UDEV

Avoid interaction with udev. LVM will manage the relevant nodes in /dev directly.

FILES¶

/etc/lvm/lvm.conf
$HOME/.lvm_history

SEE ALSO¶

lvm.conf(5), lvmcache(7), lvmthin(7), clvmd(8), dmsetup(8), lvchange(8), lvcreate(8), lvdisplay(8), lvextend(8), lvmchange(8), lvmconfig(8), lvmdiskscan(8), lvreduce(8), lvremove(8), lvrename(8), lvresize(8), lvs(8), lvscan(8), pvchange(8), pvck(8), pvcreate(8), pvdisplay(8), pvmove(8), pvremove(8), pvs(8), pvscan(8), vgcfgbackup(8), vgchange(8), vgck(8), vgconvert(8), vgcreate(8), vgdisplay(8), vgextend(8), vgimport(8), vgimportclone(8), vgmerge(8), vgmknodes(8), vgreduce(8), vgremove(8), vgrename(8), vgs(8), vgscan(8), vgsplit(8), readline(3)