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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.  Virtual devices
       may be easier to manage than physical devices, and can have capabilities beyond what the physical devices  provide  them-
       selves.  A Volume Group (VG) is a collection of one or more physical devices, each called a Physical Volume (PV).  A Log-
       ical 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 sub-
       stituted.   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 configura-
       tion 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',  '_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 dis-
       tributions.  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.  How-
       ever, there are cases where different VGs with the same name can appear to LVM, e.g. after moving disks or changing  fil-
       ters.

       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 Phys-
       ical  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 alloca-
       tion  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  alloca-
       tion/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_sepa-
       rate_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 overriden by direct use of --commandpro-
              file 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 2.02.177(2) (2017-12-18)                                         LVM(8)

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