# lvm

## NAME



           lvm — LVM tools
    


## SYNOPSIS



           **lvm**[_command_ |_file_]
    


## 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.
    
           The lvm command, and other commands listed below, are the command-
           line tools for LVM.  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".
    
           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,
           **--readonly** and **--read-only** are both accepted.
    


## 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.
           **fullreport**
                  Report information about PVs, PV segments, VGs, LVs and LV
                  segments, all at once.
           **help** Display the help text.
           **lastlog**
                  Display log report of last command run in LVM shell if
                  command log reporting is enabled.
           **lvpoll** Complete lvmpolld operations (Internal command).
           **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 LVM.
           **pvs** Report information about Physical Volumes.
           **pvscan** List 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.
           **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).
           **vgimportdevices**
                  Add PVs from a VG to the devices file.
           **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** List Volume Groups.
           **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.
           **lvmconfig**
                  Display the configuration information after loading
                  lvm.conf(5) and any other configuration files.
           **lvmdevices**
                  Manage the devices file.
           **lvmdiskscan**
                  Scan for all devices visible to LVM.
           **lvmdump**
                  Create LVM 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** List Logical Volumes.
    
           For performance metrics, use dmstats(8) or to manipulate the
           kernel device-mapper driver used by LVM directly, use dmsetup(8).
    


## VALID NAMES



           The valid characters for VG and LV names are: **a** –**z A** –**Z 0** –**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
           **metadata/record_lvs_history** 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 _/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** ', '**_iorig** ',
           '**_mimage** ', '**_mlog** ', '**_pmspare** ', '**_rimage** ', '**_rmeta** ', '**_tdata** ',
           '**_tmeta** ', '**_vdata** ', '**_vorigin** ' or '**_wcorig** '.  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.
    
           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.
    


## TAGS



           Tags are user-defined strings that can be attached to PVs, VGs and
           LVs.  Tags can be displayed with commands pvs/vgs/lvs -o tags.
           Certain commands will accept a tag name in place of a PV, VG, or
           LV name.  In these cases, the command will operate on each
           PV/VG/LV with the given tag.  Tags should be prefixed with @ to
           avoid ambiguity.
           Characters allowed in tags are: **A–Z a–z 0–9 _ + . - / = ! : # &**
    


## 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.
    


## 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.
    


## ENVIRONMENT VARIABLES



           **HOME** Directory containing _.lvm_history_ if the internal readline
                  shell is invoked.
    
           **LVM_OUT_FD**
                  File descriptor to use for common output from LVM commands.
    
           **LVM_ERR_FD**
                  File descriptor to use for error output from LVM commands.
    
           **LVM_REPORT_FD**
                  File descriptor to use for report output from LVM commands.
    
           **LVM_COMMAND_PROFILE**
                  Name of default command profile to use for LVM commands.
                  This profile is overridden by direct use of
                  **--commandprofile** command line option.
    
           **LVM_RUN_BY_DMEVENTD**
                  This variable is normally set by dmeventd plugin to inform
                  lvm command it is running from dmeventd plugin so lvm takes
                  some extra action to avoid communication and deadlocks with
                  dmeventd.
    
           **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_SUPPRESS_SYSLOG**
                  Suppress contacting syslog.
    
           **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_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 startup timestamp
                  using this format string "_%s_%d_%llu".  When set, each
                  process logs to a separate file.
    
           **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.
    
           **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.
    
           **DM_DEBUG_WITH_LINE_NUMBERS**
                  Prepends source file name and code line number with libdm
                  debugging.
    


## FILES



           _/etc/lvm/lvm.conf_
           _/etc/lvm/lvmlocal.conf_
           _$HOME/.lvm_history_
    


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