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LVM(8)									LVM(8)

       lvm - LVM2 tools

       lvm [command | file]

       lvm  provides  the command-line tools for LVM2.	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‐

       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‐

       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.

       The  following commands are built into lvm without links normally being
       created in the filesystem for them.

       dumpconfig — Display the configuration information after
	      loading lvm.conf(5) and any other configuration files.

       devtypes — Display the recognised built-in block device types.

       formats — Display recognised metadata formats.

       help — Display the help text.

       pvdata — Not implemented in LVM2.

       segtypes — Display recognised Logical Volume segment types.

       tags — Display any tags defined on this host.

       version — Display version information.

       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 special

       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 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.

       lvmchange — Change attributes of the Logical Volume Manager.

       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 commands are not implemented in LVM2 but might be in the
       future: lvmsadc, lvmsar, pvdata.

       The following options are available for many of the commands.  They are
       implemented  generically	 and  documented  here rather than repeated on
       individual manual pages.

       -h, -?, --help
	      Display the help text.

	      Display version information.

       -v, --verbose
	      Set verbose level. Repeat from 1 to  3  times  to	 increase  the
	      detail  of messages sent to stdout and stderr.  Overrides config
	      file setting.

       -d, --debug
	      Set debug level. Repeat from 1 to 6 times to increase the detail
	      of  messages sent to the log file and/or syslog (if configured).
	      Overrides config file setting.

       -q, --quiet
	      Suppress output and log messages.	 Overrides -d and -v.

       --yes  Don't prompt for confirmation interactively but  instead	always
	      assume the answer is 'yes'.  Take great care if you use this!

       -t, --test
	      Run  in  test  mode. Commands will not update metadata.  This is
	      implemented by disabling all metadata writing  but  nevertheless
	      returning	 success  to  the  calling function.  This may lead to
	      unusual error messages  in  multi-stage  operations  if  a  tool
	      relies  on  reading  back	 metadata  it believes has changed but

       --driverloaded {y|n}
	      Whether or not the device-mapper kernel driver  is  loaded.   If
	      you  set	this  to  n,  no  attempt  will be made to contact the

       -A, --autobackup {y|n}
	      Whether or not to metadata should	 be  backed  up	 automatically
	      after  a	change.	 You are strongly advised not to disable this!
	      See vgcfgbackup(8).

       -P, --partial
	      When set, the tools will do their best to provide access to Vol‐
	      ume Groups that are only partially available (one or more Physi‐
	      cal Volumes belonging to the Volume Group are missing  from  the
	      system).	 Where part of a logical volume is missing, /dev/ioer‐
	      ror will be substituted, and you could  use  dmsetup(8)  to  set
	      this  up	to  return I/O errors when accessed, or create it as a
	      large block device of nulls.  Metadata may not be	 changed  with
	      this option. To insert a replacement Physical Volume of the same
	      or large size use pvcreate -u to set the uuid to match the orig‐
	      inal followed by vgcfgrestore(8).

       -M, --metadatatype Type
	      Specifies which type of on-disk metadata to use, such as lvm1 or
	      lvm2, which can be abbreviated to	 1  or	2  respectively.   The
	      default  (lvm2)  can  be changed by setting format in the global
	      section of the config file.

	      This lets you proceed with read-only metadata operations such as
	      lvchange	-ay and vgchange -ay even if the locking module fails.
	      One use for this is in a system init script if the  lock	direc‐
	      tory is mounted read-only when the script runs.

	      Use to avoid exiting with an non-zero status code if the command
	      is run without  clustered	 locking  and  some  clustered	Volume
	      Groups have to be skipped over.

       --addtag Tag
	      Add  the tag Tag to a PV, VG or LV.  Supply this argument multi‐
	      ple times to add more than one tag at once.  A  tag  is  a  word
	      that  can	 be  used  to  group  LVM2  objects  of	 the same type
	      together.	 Tags can be given on the command line in place of PV,
	      VG  or  LV  arguments.   Tags should be prefixed with @ to avoid
	      ambiguity.  Each tag  is	expanded  by  replacing	 it  with  all
	      objects  possessing  that	 tag which are of the type expected by
	      its position on the command line.	 PVs  can  only	 possess  tags
	      while  they are part of a Volume Group: PV tags are discarded if
	      the PV is removed from the VG.  As an  example,  you  could  tag
	      some  LVs	 as  database and others as userdata and then activate
	      the database ones with lvchange -ay @database.  Objects can pos‐
	      sess  multiple  tags simultaneously.  Only the new LVM2 metadata
	      format supports tagging: objects using the LVM1 metadata	format
	      cannot be tagged because the on-disk format does not support it.
	      Characters allowed in tags are: A-Z a-z 0-9 _ + . -  and	as  of
	      version  2.02.78 the following characters are also accepted: / =
	      ! : # &

       --deltag Tag
	      Delete the tag Tag from a PV, VG or LV, if it's present.	Supply
	      this  argument  multiple	times  to  remove more than one tag at

       --alloc {anywhere|contiguous|cling|inherit|normal}
	      Selects the allocation policy when a command needs  to  allocate
	      Physical	Extents	 from the Volume Group.	 Each Volume Group and
	      Logical Volume has an allocation policy  defined.	  The  default
	      for  a  Volume  Group is normal which applies common-sense rules
	      such as not placing parallel stripes on the same	Physical  Vol‐
	      ume.   The default for a Logical Volume is inherit which applies
	      the same policy as for the Volume Group.	These policies can  be
	      changed  using  lvchange(8) and vgchange(8) or overridden on the
	      command line of any command that performs allocation.  The  con‐
	      tiguous  policy  requires	 that  new  Physical Extents be placed
	      adjacent to existing Physical Extents.  The cling policy	places
	      new  Physical  Extents  on  the same Physical Volume as existing
	      Physical Extents in the same stripe of the Logical  Volume.   If
	      there are sufficient free Physical Extents to satisfy an alloca‐
	      tion request but normal doesn't use them, anywhere will  -  even
	      if  that	reduces performance by placing two stripes on the same
	      Physical Volume.

       --profile ProfileName
	      Selects the configuration profile to use when processing an  LVM
	      command.	In addition to that, when creating a Volume Group or a
	      Logical Volume, it causes the ProfileName to be stored in	 meta‐
	      data  for each Volume Group or Logical Volume. If the profile is
	      stored in metadata, it is automatically applied  next  time  the
	      Volume  Group  or the Logical Volume is processed and the use of
	      --profile is not necessary when running  LVM  commands  further.
	      See  also	 lvm.conf(5) for more information about profile config
	      and the way it fits with other LVM configuration methods.

       --config ConfigurationString
	      Uses the ConfigurationString as direct string representation  of
	      the  configuration  to  override the existing configuration. The
	      ConfigurationString is of exactly the same format as used in any
	      LVM  configuration  file.	 See  lvm.conf(5) for more information
	      about direct config override on command line and the way it fits
	      with other LVM configuration methods.

       HOME   Directory containing .lvm_history if the internal readline shell
	      is invoked.

	      Directory containing lvm.conf(5) and  other  LVM	system	files.
	      Defaults to "/etc/lvm".

	      Suppress	warnings about openned file descriptors, when lvm com‐
	      mand is executed.

	      The Volume Group name that is assumed for	 any  reference	 to  a
	      Logical Volume that doesn't specify a path.  Not set by default.

	      Path for the lvmetad pid file.

	      Path for the lvmetad socket file.

       The following characters are valid for VG and LV names: a-z A-Z 0-9 + _
       . -

       VG and LV names cannot begin with a hyphen.   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 '..'.	A LV cannot be
       called '.' '..' 'snapshot' or 'pvmove'. The LV name may also  not  con‐
       tain the strings '_mlog', '_mimage', '_rimage', '_tdata', '_tmeta'.

       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‐

       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‐

       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

       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 and thin provisioning types
       are examples of this.

       The cache logical volume type uses a small and fast LV to  improve  the
       performance  of	a large and slow LV.  It does this by storing the fre‐
       quently used blocks on the faster LV.  LVM refers to the small fast  LV
       as a cache pool LV.  The large slow LV is called the origin LV.	Due to
       requirements from dm-cache (the kernel driver), LVM further splits  the
       cache  pool  LV into two devices - the cache data LV and cache metadata
       LV.  The cache data LV is where copies of data blocks are kept from the
       origin  LV to increase speed.  The cache metadata LV holds the account‐
       ing information that specifies where data blocks are stored  (e.g.   on
       the  origin LV or on the cache data LV).	 Users should be familiar with
       these LVs if they wish to create the best and most robust cached	 logi‐
       cal volumes.

   Cache Terms
       origin LV	   OriginLV	 large slow LV
       cache data LV	   CacheDataLV	 small fast LV for cache pool data
       cache metadata LV   CacheMetaLV	 small fast LV for cache pool metadata
       cache pool LV	   CachePoolLV	 CacheDataLV + CacheMetaLV
       cache LV		   CacheLV	 OriginLV + CachePoolLV

   Cache Steps
       The steps to create a logical volume of cache type are as follows:

       0.     Create an LV or identify an existing LV to be the origin LV.

       1.     Create  the  cache  data LV.  The size of this LV is the size of
	      the cache and will be reported as the size of the cache pool LV.

       2.     Create the cache metadata LV.  The size of  this	LV  should  be
	      1000 times smaller than the cache data LV with a minimum size of

       3.     Create the cache pool LV by combining the cache  data  LV	 (from
	      step  1)	and  cache metadata LV (from step 2).  When performing
	      this step, behavioral characteristics of the cache pool  LV  can
	      be  set.	 The  name  of the cache pool LV takes the name of the
	      cache data LV and the cache data LV and cache  metadata  LV  are
	      renamed to CachePoolLV_cdata and CachePoolLV_cmeta.

       4.     Create a cache LV by linking the cache pool LV to the origin LV.
	      The user accessible cache LV takes the name of  the  origin  LV,
	      while   the  origin  LV  becomes	a  hidden  LV  with  the  name
	      OriginLV_corig.  Users can perform this step while the origin LV
	      is in use.

       The steps above represent the best way to create a cache LV.  They pro‐
       vide the most options and have the ability to create  the  most	robust
       logical	volumes.   The examples below illustrate how these steps might
       be used in practice.

   Cache Commands
       0. create OriginLV
       lvcreate -L LargeSize -n OriginLV VG SlowPVs

       1. create CacheDataLV
       lvcreate -L CacheSize -n CacheDataLV VG FastPVs

       2. create CacheMetaLV
       lvcreate -L MetaSize -n CacheMetaLV VG FastPVs

       3. create CachePoolLV
       lvconvert --type cache-pool --poolmetadata VG/CacheMetaLV VG/CacheDataLV
       CachePoolLV takes the name of CacheDataLV.
       CacheDataLV is renamed CachePoolLV_cdata and becomes hidden.
       CacheMetaLV is renamed CachePoolLV_cmeta and becomes hidden.

       4. create CacheLV
       lvconvert --type cache --cachepool VG/CachePoolLV VG/OriginLV
       CacheLV takes the name of OriginLV.
       OriginLV is renamed OriginLV_corig and becomes hidden.

   Cache Examples
       Example 1: Creating a simple cache LV.

       0. Create the origin LV
       # lvcreate -L 10G -n lvx vg /dev/slow_dev

       1. Create a cache data LV
       # lvcreate -L 1G -n lvx_cache vg /dev/fast_dev

       2. Create a cache metadata LV (~1/1000th size of CacheDataLV or 8MiB)
       # lvcreate -L 8M -n lvx_cache_meta vg /dev/fast_dev

       3. Create a cache pool LV, combining cache data LV and cache metadata LV
       # lvconvert --type cache-pool --poolmetadata vg/lvx_cache_meta \

       4. Create a cached LV by combining the cache pool LV and origin LV
       # lvconvert --type cache --cachepool vg/lvx_cache vg/lvx

       Example 2: Creating a cache LV with a fault tolerant cache pool LV.

       Users who are concerned about the possibility of failures in their fast
       devices	that could lead to data loss might consider making their cache
       pool sub-LVs redundant.	Example 2 illustrates how to  do  that.	  Note
       that only steps 1 & 2 change.

       0. Create an origin LV we wish to cache
       # lvcreate -L 10G -n lvx vg /dev/slow_devs

       1. Create a 2-way RAID1 cache data LV
       # lvcreate --type raid1 -m 1 -L 1G -n lvx_cache vg \
	    /dev/fast1 /dev/fast2

       2. Create a 2-way RAID1 cache metadata LV
       # lvcreate --type raid1 -m 1 -L 8M -n lvx_cache_meta vg \
	    /dev/fast1 /dev/fast2

       3. Create a cache pool LV combining cache data LV and cache metadata LV
       # lvconvert --type cache-pool --poolmetadata vg/lvx_cache_meta \

       4. Create a cached LV by combining the cache pool LV and origin LV
       # lvconvert --type cache --cachepool vg/lvx_cache vg/lvx

       Example 3: Creating a simple cache LV with writethough caching.

       Some  users wish to ensure that any data written will be stored both in
       the cache pool LV and on the origin LV.	The loss of a  device  associ‐
       ated with the cache pool LV in this case would not mean the loss of any
       data.  When combining the cache data LV and the cache  metadata	LV  to
       form  the  cache pool LV, properties of the cache can be specified - in
       this case, writethrough vs.  writeback.	 Note  that  only  step	 3  is
       affected in this case.

       0. Create an origin LV we wish to cache (yours may already exist)
       # lvcreate -L 10G -n lvx vg /dev/slow

       1. Create a cache data LV
       # lvcreate -L 1G -n lvx_cache vg /dev/fast

       2. Create a cache metadata LV
       # lvcreate -L 8M -n lvx_cache_meta vg /dev/fast

       3. Create a cache pool LV specifying cache mode "writethrough"
       # lvconvert --type cache-pool --poolmetadata vg/lvx_cache_meta \
	    --cachemode writethrough vg/lvx_cache

       4. Create a cache LV by combining the cache pool LV and origin LV
       # lvconvert --type cache --cachepool vg/lvx_cache vg/lvx

   Removing Cache Logical Volumes
       If  you	wish to remove all logical volumes associated with a cache LV,
       you must remove both top-level, user-visible devices.  The cache	 meta‐
       data  LV	 and  cache  data  LV cannot be removed directly.  If only the
       cache pool LV is specfied for removal, any cached blocks not yet on the
       origin LV will be flush, the cache pool LV will be removed, and the now
       un-cached origin LV will remain.	 If the user specifies a cache LV  for
       removal,	 then the origin LV is removed and only the cache pool LV will
       remain.	The cache pool LV can then be used to create another cache  LV
       with a different origin LV if desired.

       When users intend to remove all logical volumes associated with a cache
       LV, it is generally better to start with the origin LV and then	remove
       the  cache  pool	 LV.   If  the operations are performed in the reverse
       order, the user will have to wait for the contents of the cache pool LV
       to  be  flushed	before the origin LV is removed.  This could take some

       All tools return a status code of zero on success or non-zero on	 fail‐


       lvm.conf(5),  lvm dumpconfig(8),	 clvmd(8),  lvchange(8),  lvcreate(8),
       lvdisplay(8), lvextend(8), lvmchange(8),	 lvmdiskscan(8),  lvreduce(8),
       lvremove(8),  lvrename(8), lvresize(8), lvs(8), lvscan(8), pvchange(8),
       pvck(8), pvcreate(8),  pvdisplay(8),  pvmove(8),	 pvremove(8),  pvs(8),
       pvscan(8),  vgcfgbackup(8),  vgchange(8), vgck(8), vgconvert(8), vgcre‐
       ate(8),	vgdisplay(8),  vgextend(8),   vgimport(8),   vgimportclone(8),
       vgmerge(8),   vgmknodes(8),   vgreduce(8),   vgremove(8),  vgrename(8),
       vgs(8), vgscan(8), vgsplit(8), readline(3)

Sistina Software UK   LVM TOOLS 2.02.106(2) (2014-04-10)		LVM(8)

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