lvm(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | BUILT-IN COMMANDS | COMMANDS | VALID NAMES | UNIQUE NAMES | ALLOCATION | LOGICAL VOLUME TYPES | DIAGNOSTICS | ENVIRONMENT VARIABLES | FILES | SEE ALSO | COLOPHON

LVM(8)                   System Manager's Manual                  LVM(8)

NAME         top

       lvm — LVM2 tools

SYNOPSIS         top

       lvm [command|file]

DESCRIPTION         top

       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".  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         top

       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         top

       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).
       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 Scan all disks for 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 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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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
              lvm2 command it is running from dmeventd plugin so lvm2
              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         top

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

SEE ALSO         top

       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), lvmpolld(8), lvmlockd(8), lvmlockctl(8),
       cmirrord(8), lvmdbusd(8),

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

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

COLOPHON         top

       This page is part of the lvm2 (Logical Volume Manager 2) project.
       Information about the project can be found at 
       ⟨http://www.sourceware.org/lvm2/⟩.  If you have a bug report for
       this manual page, see ⟨https://github.com/lvmteam/lvm2/issues⟩.
       This page was obtained from the tarball
       https://github.com/lvmteam/lvm2/archive/refs/tags/v2_03_13.tar.gz
       fetched from ⟨https://github.com/lvmteam/lvm2/releases⟩ on
       2021-08-27.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
       to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to
       man-pages@man7.org

Red Hat, Inc.       LVM TOOLS 2.03.13(2) (2021-08-11)             LVM(8)

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