lvm — LVM2 tools
The Logical Volume Manager (LVM) provides tools to create virtual block devices
from physical devices. Virtual devices may be easier to manage than physical
devices, and can have capabilities beyond what the physical devices provide
themselves. A Volume Group (VG) is a collection of one or more physical
devices, each called a Physical Volume (PV). A Logical Volume (LV) is a
virtual block device that can be used by the system or applications. Each
block of data in an LV is stored on one or more PV in the VG, according to
algorithms implemented by Device Mapper (DM) in the kernel.
The lvm command, and other commands listed below, are the command-line tools for
LVM. A separate manual page describes each command in detail.
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.
is invoked with argv 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
will display all the LVs in "vg0". Tags can
also be used - see --addtag
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
Additional hyphens within option names are ignored. For example,
are both accepted.
The following commands are built into lvm without links normally being created
in the filesystem for them.
- The same as lvmconfig(8) below.
- Display the recognised built-in block device types.
- The same as lvmconfig(8) below.
- Display recognised metadata formats.
- Report information about PVs, PV segments, VGs, LVs and LV
segments, all at once.
- Display the help text.
- Display log report of last command run in LVM shell if
command log reporting is enabled.
- Complete lvmpolld operations (Internal command).
- Display recognised Logical Volume segment types.
- Display any system ID currently set on this host.
- Display any tags defined on this host.
- Display version information.
The following commands implement the core LVM functionality.
- Change attributes of a Physical Volume.
- Check Physical Volume metadata.
- Initialize a disk or partition for use by LVM.
- Display attributes of a Physical Volume.
- Move Physical Extents.
- Remove a Physical Volume.
- Resize a disk or partition in use by LVM2.
- Report information about Physical Volumes.
- Scan all disks for Physical Volumes.
- Backup Volume Group descriptor area.
- Restore Volume Group descriptor area.
- Change attributes of a Volume Group.
- Check Volume Group metadata.
- Convert Volume Group metadata format.
- Create a Volume Group.
- Display attributes of Volume Groups.
- Make volume Groups unknown to the system.
- Add Physical Volumes to a Volume Group.
- Make exported Volume Groups known to the system.
- Import and rename duplicated Volume Group (e.g. a hardware
- Merge two Volume Groups.
- Recreate Volume Group directory and Logical Volume special
- Reduce a Volume Group by removing one or more Physical
- Remove a Volume Group.
- Rename a Volume Group.
- Report information about Volume Groups.
- Scan all disks for Volume Groups and rebuild caches.
- Split a Volume Group into two, moving any logical volumes
from one Volume Group to another by moving entire Physical Volumes.
- Change attributes of a Logical Volume.
- Convert a Logical Volume from linear to mirror or
- Create a Logical Volume in an existing Volume Group.
- Display attributes of a Logical Volume.
- Extend the size of a Logical Volume.
- Display the configuration information after loading
lvm.conf(5) and any other configuration files.
- Scan for all devices visible to LVM2.
- Create lvm2 information dumps for diagnostic purposes.
- Reduce the size of a Logical Volume.
- Remove a Logical Volume.
- Rename a Logical Volume.
- Resize a Logical Volume.
- Report information about Logical Volumes.
- Scan (all disks) for Logical Volumes.
The following LVM1 commands are not implemented in LVM2: lvmchange
. For performance metrics, use
(8) or to manipulate the kernel device-mapper driver used by
LVM2 directly, use dmsetup
The valid characters for VG and LV names are: a
-9 + _ . -
VG names cannot begin with a hyphen. The name of a new LV also cannot begin with
a hyphen. However, if the configuration setting
is enabled then an LV name with a hyphen as
a prefix indicates that, although the LV was removed, it is still being
tracked because it forms part of the history of at least one LV that is still
present. This helps to record the ancestry of thin snapshots even after some
links in the chain have been removed. A reference to the historical LV 'lvol1'
in VG 'vg00' would be 'vg00/\-lvol1' or just '-lvol1' if the VG is already
set. (The latter form must be preceded by '--' to terminate command line
option processing before reaching this argument.)
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
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
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
out the original VG, LV and internal layer 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
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
(7).) In this case, the one VG that is not foreign is
assumed to be the intended VG and is processed.
LV names are unique within a VG. The name of an historical LV cannot be reused
until the historical LV has itself been removed or renamed.
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
) and ending with the allocation policy specified using
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:
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.
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
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
When a Logical Volume is striped or mirrored, the above restrictions are applied
independently to each stripe or mirror image (leg) that needs space.
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
configuration parameter is
set to 0, it will then allow the log to share Physical Volume(s) with part of
When allocating thin pool metadata, similar considerations to those of a mirror
log in the last paragraph apply based on the value of the
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) 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
Some logical volume types are simple to create and can be done with a single
(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 (
(7)) types are examples of this.
All tools return a status code of zero on success or non-zero on failure. The
non-zero codes distinguish only between the broad categories of unrecognised
commands, problems processing the command line arguments and any other
failures. As LVM remains under active development, the code used in a specific
case occasionally changes between releases. Message text may also change.
- Directory containing .lvm_history if the internal
readline shell is invoked.
- File descriptor to use for common output from LVM
- File descriptor to use for error output from LVM
- File descriptor to use for report output from LVM
- Name of default command profile to use for LVM commands.
This profile is overriden by direct use of --commandprofile command
- This variable is normally set by dmeventd plugin to inform
lvm2 command it is running from dmeventd plugin so lvm2 takes some extra
action to avoid comunication and deadlocks with dmeventd.
- Directory containing lvm.conf(5) and other LVM
system files. Defaults to " /etc/lvm".
- Suppress warnings about unexpected file descriptors passed
- The Volume Group name that is assumed for any reference to
a Logical Volume that doesn't specify a path. Not set by default.
- Path to the file that stores the lvmetad process ID.
- Path to the socket used to communicate with lvmetad.
- Path to the file that stores the lvmpolld process ID.
- Path to the socket used to communicate with lvmpolld..
- A string of up to 32 letters appended to the log filename
and followed by the process ID and a startup timestamp using this format
string "_%s_%d_%llu". When set, each process logs to a separate
- If more than this number of lines are sent to the log file,
the command gets aborted. Automated tests use this to terminate looping
- 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.
- Used to suppress warning messages when the configured
locking is known to be unavailable.
- Abort processing if the code detects a non-fatal internal
- Avoid interaction with udev. LVM will manage the relevant
nodes in /dev directly.