lvm2/man/lvm.8_main

.TH LVM 8 "LVM TOOLS #VERSION#" "Red Hat, Inc." \" -*- nroff -*-
.
.SH NAME
.
lvm \(em LVM2 tools
.
.SH SYNOPSIS
.
.B lvm
.RI [ command | file ]
.
.SH DESCRIPTION
.

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.
.P

The lvm command, and other commands listed below, are the command-line
tools for LVM.  A separate manual page describes each command in detail.
.P
If \fBlvm\fP 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 \fBreadline\fP(3) for details.
.P
If \fBlvm\fP 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.
.P
On invocation, \fBlvm\fP 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
.B LVM_SUPPRESS_FD_WARNINGS\fP.
.P
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 \fBlvdisplay vg0\fP will display all the LVs in "vg0".
Tags can also be used - see \fB--addtag\fP below.
.P
One advantage of using the built-in shell is that configuration
information gets cached internally between commands.
.P
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 \fBlvm\fP.
.P
Additional hyphens within option names are ignored.  For example,
\fB--readonly\fP and \fB--read-only\fP are both accepted.
.
.SH BUILT-IN COMMANDS
.
The following commands are built into lvm without links
normally being created in the filesystem for them.
.sp
.PD 0
.TP 14
.B config
The same as \fBlvmconfig\fP(8) below.
.TP
.B devtypes
Display the recognised built-in block device types.
.TP
.B dumpconfig
The same as \fBlvmconfig\fP(8) below.
.TP
.B formats
Display recognised metadata formats.
.TP
.B fullreport
Report information about PVs, PV segments, VGs, LVs and LV segments,
all at once.
.TP
.B help
Display the help text.
.TP
.B lastlog
Display log report of last command run in LVM shell
if command log reporting is enabled.
.TP
.B lvpoll
Complete lvmpolld operations (Internal command).
.TP
.B segtypes
Display recognised Logical Volume segment types.
.TP
.B systemid
Display any system ID currently set on this host.
.TP
.B tags
Display any tags defined on this host.
.TP
.B version
Display version information.
.PD
.
.SH COMMANDS
.
The following commands implement the core LVM functionality.
.sp
.PD 0
.TP 14
.B pvchange
Change attributes of a Physical Volume.
.TP
.B pvck
Check Physical Volume metadata.
.TP
.B pvcreate
Initialize a disk or partition for use by LVM.
.TP
.B pvdisplay
Display attributes of a Physical Volume.
.TP
.B pvmove
Move Physical Extents.
.TP
.B pvremove
Remove a Physical Volume.
.TP
.B pvresize
Resize a disk or partition in use by LVM2.
.TP
.B pvs
Report information about Physical Volumes.
.TP
.B pvscan
Scan all disks for Physical Volumes.
.TP
.B vgcfgbackup
Backup Volume Group descriptor area.
.TP
.B vgcfgrestore
Restore Volume Group descriptor area.
.TP
.B vgchange
Change attributes of a Volume Group.
.TP
.B vgck
Check Volume Group metadata.
.TP
.B vgconvert
Convert Volume Group metadata format.
.TP
.B vgcreate
Create a Volume Group.
.TP
.B vgdisplay
Display attributes of Volume Groups.
.TP
.B vgexport
Make volume Groups unknown to the system.
.TP
.B vgextend
Add Physical Volumes to a Volume Group.
.TP
.B vgimport
Make exported Volume Groups known to the system.
.TP
.B vgimportclone
Import and rename duplicated Volume Group (e.g. a hardware snapshot).
.TP
.B vgimportdevices
Add PVs from a VG to the devices file.
.TP
.B vgmerge
Merge two Volume Groups.
.TP
.B vgmknodes
Recreate Volume Group directory and Logical Volume special files
.TP
.B vgreduce
Reduce a Volume Group by removing one or more Physical Volumes.
.TP
.B vgremove
Remove a Volume Group.
.TP
.B vgrename
Rename a Volume Group.
.TP
.B vgs
Report information about Volume Groups.
.TP
.B vgscan
Scan all disks for Volume Groups.
.TP
.B vgsplit
Split a Volume Group into two, moving any logical
volumes from one Volume Group to another by moving entire Physical
Volumes.
.TP
.B lvchange
Change attributes of a Logical Volume.
.TP
.B lvconvert
Convert a Logical Volume from linear to mirror or snapshot.
.TP
.B lvcreate
Create a Logical Volume in an existing Volume Group.
.TP
.B lvdisplay
Display attributes of a Logical Volume.
.TP
.B lvextend
Extend the size of a Logical Volume.
.TP
.B lvmconfig
Display the configuration information after
loading \fBlvm.conf\fP(5) and any other configuration files.
.TP
.B lvmdevices
Manage the devices file.
.TP
.B lvmdiskscan
Scan for all devices visible to LVM2.
.TP
.B lvmdump
Create lvm2 information dumps for diagnostic purposes.
.TP
.B lvreduce
Reduce the size of a Logical Volume.
.TP
.B lvremove
Remove a Logical Volume.
.TP
.B lvrename
Rename a Logical Volume.
.TP
.B lvresize
Resize a Logical Volume.
.TP
.B lvs
Report information about Logical Volumes.
.TP
.B lvscan
Scan (all disks) for Logical Volumes.
.PD
.P
The following LVM1 commands are not implemented in LVM2:
.BR lvmchange ", " lvmsadc ", " lvmsar ", " pvdata .
For performance metrics, use \fBdmstats\fP(8) or to manipulate the kernel
device-mapper driver used by LVM2 directly, use \fBdmsetup\fP(8).
.
.SH VALID NAMES
.
The valid characters for VG and LV names are:
.BR a - z
.BR A - Z
.BR 0 - 9
.BR "+ _ . -"
.P
VG names cannot begin with a hyphen.
The name of a new LV also cannot begin with a hyphen.  However, if the
configuration setting \fBmetadata/record_lvs_history\fP 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.)
.P
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
\fI/dev/\fP 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:
\fR'_cdata', '_cmeta', '_corig', '_mlog', '_mimage', '_pmspare',
\fR'_rimage', '_rmeta', '_tdata', '_tmeta', '_vorigin' or '_vdata'.
A directory bearing the name of each Volume Group is created under
\fI/dev\fP 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 \fI/dev/mapper\fP 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
\fI/dev/VolumeGroupName/LogicalVolumeName\fP 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 \fBdmsetup splitname\fP to separate out the
original VG, LV and internal layer names.
.P
.
.SH 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
.BR lvmsystemid (7).)
In this case, the one VG that is not foreign is assumed to be the intended
VG and is processed.
.P
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.

.
.SH 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 (\fBcontiguous\fP) and ending with the allocation policy specified
using \fB--alloc\fP 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:

\fBContiguous\fP 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.

\fBCling\fP 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 \fBallocation/cling_tag_list\fP 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.

\fBNormal\fP 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
.B 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
.B 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 \fBlvcreate\fP(8) and \fBlvconvert\fP(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 \fB-vvvv\fP to
a command.
.
.SH LOGICAL VOLUME TYPES
.
Some logical volume types are simple to create and can be done with a
single \fBlvcreate\fP(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 (\fBlvmcache\fP(7))
and thin provisioning (\fBlvmthin\fP(7)) types are examples of this.
.
.SH DIAGNOSTICS
.
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.
.
.SH ENVIRONMENT VARIABLES
.
.TP
.B HOME
Directory containing \fI.lvm_history\fP if the internal readline
shell is invoked.
.TP
.B LVM_OUT_FD
File descriptor to use for common output from LVM commands.
.TP
.B LVM_ERR_FD
File descriptor to use for error output from LVM commands.
.TP
.B LVM_REPORT_FD
File descriptor to use for report output from LVM commands.
.TP
.B LVM_COMMAND_PROFILE
Name of default command profile to use for LVM commands. This profile
is overridden by direct use of \fB--commandprofile\fP command line option.
.TP
.B LVM_RUN_BY_DMEVENTD
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 communication and deadlocks with dmeventd.
.TP
.B LVM_SYSTEM_DIR
Directory containing \fBlvm.conf\fP(5) and other LVM system files.
Defaults to "\fI#DEFAULT_SYS_DIR#\fP".
.TP
.B LVM_SUPPRESS_FD_WARNINGS
Suppress warnings about unexpected file descriptors passed into LVM.
.TP
.B LVM_SUPPRESS_SYSLOG
Suppress contacting syslog.
.TP
.B 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.
.TP
.B LVM_LVMPOLLD_PIDFILE
Path to the file that stores the lvmpolld process ID.
.TP
.B LVM_LVMPOLLD_SOCKET
Path to the socket used to communicate with lvmpolld..
.TP
.B LVM_LOG_FILE_EPOCH
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 file.
.TP
.B LVM_LOG_FILE_MAX_LINES
If more than this number of lines are sent to the log file, the command gets
aborted.  Automated tests use this to terminate looping commands.
.TP
.B 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.
.B LVM_LOG_FILE_EPOCH
and
.B LVM_EXPECTED_EXIT_STATUS
together allow automated test scripts to discard uninteresting log data.
.TP
.B LVM_SUPPRESS_LOCKING_FAILURE_MESSAGES
Used to suppress warning messages when the configured locking is known
to be unavailable.
.TP
.B DM_ABORT_ON_INTERNAL_ERRORS
Abort processing if the code detects a non-fatal internal error.
.TP
.B DM_DISABLE_UDEV
Avoid interaction with udev.  LVM will manage the relevant nodes in /dev
directly.
.TP
.B DM_DEBUG_WITH_LINE_NUMBERS
Prepends source file name and code line number with libdm debugging.
.
.SH FILES
.
.I #DEFAULT_SYS_DIR#/lvm.conf
.br
.I $HOME/.lvm_history
.
.SH SEE ALSO
.
.nh
.BR lvm (8)
.BR lvm.conf (5)
.BR lvmconfig (8)

.BR pvchange (8)
.BR pvck (8)
.BR pvcreate (8)
.BR pvdisplay (8)
.BR pvmove (8)
.BR pvremove (8)
.BR pvresize (8)
.BR pvs (8)
.BR pvscan (8) 

.BR vgcfgbackup (8)
.BR vgcfgrestore (8)
.BR vgchange (8)
.BR vgck (8)
.BR vgcreate (8)
.BR vgconvert (8)
.BR vgdisplay (8)
.BR vgexport (8)
.BR vgextend (8)
.BR vgimport (8)
.BR vgimportclone (8)
.BR vgmerge (8)
.BR vgmknodes (8)
.BR vgreduce (8)
.BR vgremove (8)
.BR vgrename (8)
.BR vgs (8)
.BR vgscan (8)
.BR vgsplit (8) 

.BR lvcreate (8)
.BR lvchange (8)
.BR lvconvert (8)
.BR lvdisplay (8)
.BR lvextend (8)
.BR lvreduce (8)
.BR lvremove (8)
.BR lvrename (8)
.BR lvresize (8)
.BR lvs (8)
.BR lvscan (8)

.BR lvm-fullreport (8)
.BR lvm-lvpoll (8)
.BR lvm2-activation-generator (8)
.BR blkdeactivate (8)
.BR lvmdump (8)

.BR dmeventd (8)
.BR lvmpolld (8)
.BR lvmlockd (8)
.BR lvmlockctl (8)
.BR cmirrord (8)
.BR lvmdbusd (8)

.BR lvmsystemid (7)
.BR lvmreport (7)
.BR lvmraid (7)
.BR lvmthin (7)
.BR lvmcache (7)

.BR dmsetup (8),
.BR dmstats (8),
.BR readline (3)