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> man lvm
LVM(8)                                         System Manager's Manual                                        LVM(8)

NAME
       lvm — LVM2 tools

SYNOPSIS
       lvm [command|file]

DESCRIPTION
       The  Logical Volume Manager (LVM) provides tools to create virtual block devices from physical devices.  Vir‐
       tual devices may be easier to manage than physical devices, and can have capabilities beyond what the  physi‐
       cal  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  sys‐
       tem  or  applications.  Each block of data in an LV is stored on one or more PV in the VG, according to algo‐
       rithms 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  his‐
       tory 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.

       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 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.
       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 LVM1 commands are not implemented in LVM2: lvmchange, lvmsadc, lvmsar, pvdata.  For performance
       metrics, use dmstats(8) or to  manipulate  the  kernel  device-mapper  driver  used  by  LVM2  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  indi‐
       cates 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  ter‐
       minate 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',  '_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 amend‐
       ment 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.

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 Vol‐
       ume  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 param‐
       eter 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 proper‐
       ties (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  alloca‐
       tion/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 impor‐
       tant  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 occasion‐
       ally 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 overriden by  direct  use  of
              --commandprofile command line option.

       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 comunication 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_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 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.

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

SEE ALSO
       lvm(8) lvm.conf(5) lvmconfig(8)

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

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

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

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

       dmeventd(8) lvmetad(8) lvmpolld(8) lvmlockd(8) lvmlockctl(8) clvmd(8) cmirrord(8) lvmdbusd(8)

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

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

Red Hat, Inc.                         LVM TOOLS 2.02.171(2)-RHEL7 (2017-05-03)                                LVM(8)