lvm(8) - phpMan

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 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
       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 com-
       mand (for example by using a hard or soft link) it acts  as  that  com-
       mand.
       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_SUP-
       PRESS_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 substi-
       tuted.  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 infor-
       mation 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  hard-
                     ware snapshot).
       vgmerge       Merge two Volume Groups.
       vgmknodes     Recreate  Volume  Group directory and Logical Volume spe-
                     cial 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  Physi-
                     cal Volumes.
       lvchange      Change attributes of a Logical Volume.
       lvconvert     Convert  a  Logical Volume from linear to mirror or snap-
                     shot.
       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 meta-
       data/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', '_rim-
       age', '_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  accessi-
       ble  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/Vol-
       umeGroupName/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 spec-
       ified  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  for-
       eign  (see  lvmsystemid(7).)  In this case, the one VG that is not for-
       eign 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 con-
       sidered.
       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  Logi-
       cal  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 configura-
       tion 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 Vol-
       ume (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  Physi-
       cal  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 param-
       eter.
       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  Vol-
       umes  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 pro-
       visioning (lvmthin(7)) types are examples of this.
DIAGNOSTICS
       All tools return a status code of zero on success or non-zero on  fail-
       ure.   The non-zero codes distinguish only between the broad categories
       of unrecognised commands, problems processing the  command  line  argu-
       ments 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 --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.
       DM_DEBUG_WITH_LINE_NUMBERS
              Prepends source file name and code line number with libdm debug-
              ging.
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 2.02.187(2)-RHEL7 (2020-03-24)             LVM(8)