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LVM


Section: Maintenance Commands (8)
Updated: LVM TOOLS 2.02.100(2)-RHEL6 (2013-10-23)
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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 enviromental 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.


dumpconfig — Display the configuration information after

loading lvm.conf(5) and any other configuration files.
formats — Display recognised metadata formats.

help — Display the help text.

pvdata — Not implemented in LVM2.

segtypes — Display recognised Logical Volume segment types.

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.

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.


-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.
–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).
-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.
–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.
–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.
–profile ProfileName


Selects the configuration profile to use when processing an LVM command.
In addition to that, when creating a Volume Group or a Logical Volume,
it causes the ProfileName to be stored in metadata for each Volume Group
or Logical Volume. If the profile is stored in metadata, it is automatically
applied next time the Volume Group or the Logical Volume is processed and the
use of –profile is not necessary when running LVM commands further. See also
lvm.conf(5) for more information about profile config and the
way it fits with other LVM configuration methods.
–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.

 

ENVIRONMENT VARIABLES


HOME


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


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


Suppress warnings about openned file descriptors, when lvm command
is executed.
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.

 

VALID NAMES

The following characters are valid for VG and LV names:
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 ‘..’.
A LV cannot be called ‘.’ ‘..’ ‘snapshot’ or ‘pvmove’. The LV name may also not contain
the strings ‘_mlog’, ‘_mimage’, ‘_rimage’, ‘_tdata’, ‘_tmeta’.
 

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.
 

DIAGNOSTICS

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

FILES

/etc/lvm/lvm.conf


$HOME/.lvm_history

 

SEE ALSO

lvm.conf(5),

clvmd(8),

lvchange(8),

lvcreate(8),

lvdisplay(8),

lvextend(8),

lvmchange(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)



 

Index



NAME

SYNOPSIS

DESCRIPTION

BUILT-IN COMMANDS

COMMANDS

OPTIONS

ENVIRONMENT VARIABLES

VALID NAMES

ALLOCATION

DIAGNOSTICS

FILES

SEE ALSO



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