Ubuntu Manpage: pvcreate — Initialize physical volume(s) for use by LVM

Provided by: lvm2_2.03.22-1ubuntu2_amd64

NAME

       pvcreate — Initialize physical volume(s) for use by LVM

SYNOPSIS

       pvcreate position_args
           [ option_args ]

DESCRIPTION

pvcreate initializes a Physical Volume (PV) on a device so the device is recognized as belonging to LVM.
This allows the PV to be used in a Volume Group (VG). An LVM disk label is written to the device, and
LVM metadata areas are initialized. A PV can be placed on a whole device or partition.

Use vgcreate(8) to create a new VG on the PV, or vgextend(8) to add the PV to an existing VG. Use
pvremove(8) to remove the LVM disk label from the device.

The force option will create a PV without confirmation. Repeating the force option (-ff) will forcibly
create a PV, overriding checks that normally prevent it, e.g. if the PV is already in a VG.

Metadata location, size, and alignment

The LVM disk label begins 512 bytes from the start of the device, and is 512 bytes in size.

The LVM metadata area begins at an offset (from the start of the device) equal to the page size of the
machine creating the PV (often 4 KiB.) The metadata area contains a 512 byte header and a multi-KiB
circular buffer that holds text copies of the VG metadata.

With default settings, the first physical extent (PE), which contains LV data, is 1 MiB from the start of
the device. This location is controlled by default_data_alignment in lvm.conf, which is set to 1 (MiB)
by default. The pe_start will be a multiple of this many MiB. This location can be checked with:
pvs -o pe_start PV

The size of the LVM metadata area is the space between the the start of the metadata area and the first
PE. When metadata begins at 4 KiB and the first PE is at 1024 KiB, the metadata area size is 1020 KiB.
This can be checked with:
pvs -o mda_size PV

The mda_size cannot be increased after pvcreate, so if larger metadata is needed, it must be set during
pvcreate. Two copies of the VG metadata must always fit within the metadata area, so the maximum VG
metadata size is around half the mda_size. This can be checked with:
vgs -o mda_free VG

A larger metadata area can be set with --metadatasize. The resulting mda_size may be larger than
specified due to default_data_alignment placing pe_start on a MiB boundary, and the fact that the
metadata area extends to the first PE. With metadata starting at 4 KiB and default_data_alignment 1
(MiB), setting --metadatasize 2048k results in pe_start of 3 MiB and mda_size of 3068 KiB.
Alternatively, --metadatasize 2044k results in pe_start at 2 MiB and mda_size of 2044 KiB.

The alignment of pe_start described above may be automatically overridden based on md device properties
or device i/o properties reported in sysfs. These automatic adjustments can be enabled/disabled using
lvm.conf settings md_chunk_alignment and data_alignment_offset_detection.

To use a different pe_start alignment, use the --dataalignment option. The --metadatasize option would
also typically be used in this case because the metadata area size also determines the location of
pe_start. When using these two options together, pe_start is calculated as: metadata area start (page
size), plus the specified --metadatasize, rounded up to the next multiple of --dataalignment. With
metadata starting at 4 KiB, --metadatasize 2048k, and --dataalignment 128k, pe_start is 2176 KiB and
mda_size is 2172 KiB. The pe_start of 2176 KiB is the nearest even multiple of 128 KiB that provides at
least 2048 KiB of metadata space. Always check the resulting alignment and metadata size when using
these options.

To shift an aligned pe_start value, use the --dataalignmentoffset option. The pe_start alignment is
calculated as described above, and then the value specified with --dataalignmentoffset is added to
produce the final pe_start value.

USAGE

       pvcreate PV ...
           [ -f|--force ]
           [ -M|--metadatatype lvm2 ]
           [ -u|--uuid String ]
           [ -Z|--zero y|n ]
           [    --dataalignment Size[k|UNIT] ]
           [    --dataalignmentoffset Size[k|UNIT] ]
           [    --bootloaderareasize Size[m|UNIT] ]
           [    --labelsector Number ]
           [    --[pv]metadatacopies 0|1|2 ]
           [    --metadatasize Size[m|UNIT] ]
           [    --metadataignore y|n ]
           [    --norestorefile ]
           [    --setphysicalvolumesize Size[m|UNIT] ]
           [    --reportformat basic|json|json_std ]
           [    --restorefile String ]
           [ COMMON_OPTIONS ]

       Common options for lvm:
           [ -d|--debug ]
           [ -h|--help ]
           [ -q|--quiet ]
           [ -t|--test ]
           [ -v|--verbose ]
           [ -y|--yes ]
           [    --commandprofile String ]
           [    --config String ]
           [    --devices PV ]
           [    --devicesfile String ]
           [    --driverloaded y|n ]
           [    --journal String ]
           [    --lockopt String ]
           [    --longhelp ]
           [    --nohints ]
           [    --nolocking ]
           [    --profile String ]
           [    --version ]

OPTIONS

--bootloaderareasize Size[m|UNIT]
Reserve space for the bootloader between the LVM metadata area and the first PE. The bootloader
area is reserved for bootloaders to embed their own data or metadata; LVM will not use it. The
bootloader area begins where the first PE would otherwise be located. The first PE is moved out
by the size of the bootloader area, and then moved out further if necessary to match the data
alignment. The start of the bootloader area is always aligned, see also --dataalignment and
--dataalignmentoffset. The bootloader area may be larger than requested due to the alignment, but
it's never less than the requested size. To see the bootloader area start and size of an existing
PV use pvs -o +pv_ba_start,pv_ba_size.

--commandprofile String
The command profile to use for command configuration. See lvm.conf(5) for more information about
profiles.

--config String
Config settings for the command. These override lvm.conf(5) settings. The String arg uses the
same format as lvm.conf(5), or may use section/field syntax. See lvm.conf(5) for more information
about config.

--dataalignment Size[k|UNIT]
Align the start of a PV data area with a multiple of this number. To see the location of the
first Physical Extent (PE) of an existing PV, use pvs -o +pe_start. In addition, it may be shifted
by an alignment offset, see --dataalignmentoffset. Also specify an appropriate PE size when
creating a VG.

--dataalignmentoffset Size[k|UNIT]
Shift the start of the PV data area by this additional offset.

-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).

--devices PV
Restricts the devices that are visible and accessible to the command. Devices not listed will
appear to be missing. This option can be repeated, or accepts a comma separated list of devices.
This overrides the devices file.

--devicesfile String
A file listing devices that LVM should use. The file must exist in /etc/lvm/devices/ and is
managed with the lvmdevices(8) command. This overrides the lvm.conf(5) devices/devicesfile and
devices/use_devicesfile settings.

--driverloaded y|n
If set to no, the command will not attempt to use device-mapper. For testing and debugging.

-f|--force ...
Override various checks, confirmations and protections. Use with extreme caution.

-h|--help
Display help text.

--journal String
Record information in the systemd journal. This information is in addition to information enabled
by the lvm.conf log/journal setting. command: record information about the command. output:
record the default command output. debug: record full command debugging.

--labelsector Number
By default the PV is labelled with an LVM2 identifier in its second sector (sector 1). This lets
you use a different sector near the start of the disk (between 0 and 3 inclusive - see
LABEL_SCAN_SECTORS in the source). Use with care.

--lockopt String
Used to pass options for special cases to lvmlockd. See lvmlockd(8) for more information.

--longhelp
Display long help text.

--metadataignore y|n
Specifies the metadataignore property of a PV. If yes, metadata areas on the PV are ignored, and
lvm will not store metadata in the metadata areas of the PV. If no, lvm will store metadata on
the PV.

--metadatasize Size[m|UNIT]
The approximate amount of space used for each VG metadata area. The size may be rounded.

-M|--metadatatype lvm2
Specifies the type of on-disk metadata to use. lvm2 (or just 2) is the current, standard format.
lvm1 (or just 1) is no longer used.

--nohints
Do not use the hints file to locate devices for PVs. A command may read more devices to find PVs
when hints are not used. The command will still perform standard hint file invalidation where
appropriate.

--nolocking
Disable locking. Use with caution, concurrent commands may produce incorrect results.

--norestorefile
In conjunction with --uuid, this allows a uuid to be specified without also requiring that a
backup of the metadata be provided.

--profile String
An alias for --commandprofile or --metadataprofile, depending on the command.

--[pv]metadatacopies 0|1|2
The number of metadata areas to set aside on a PV for storing VG metadata. When 2, one copy of
the VG metadata is stored at the front of the PV and a second copy is stored at the end. When 1,
one copy of the VG metadata is stored at the front of the PV. When 0, no copies of the VG
metadata are stored on the given PV. This may be useful in VGs containing many PVs (this places
limitations on the ability to use vgsplit later.)

-q|--quiet ...
Suppress output and log messages. Overrides --debug and --verbose. Repeat once to also suppress
any prompts with answer 'no'.

--reportformat basic|json|json_std
Overrides current output format for reports which is defined globally by the report/output_format
setting in lvm.conf(5). basic is the original format with columns and rows. If there is more
than one report per command, each report is prefixed with the report name for identification. json
produces report output in JSON format. json_std produces report output in JSON format which is
more compliant with JSON standard. See lvmreport(7) for more information.

--restorefile String
In conjunction with --uuid, this reads the file (produced by vgcfgbackup), extracts the location
and size of the data on the PV, and ensures that the metadata produced by the program is
consistent with the contents of the file, i.e. the physical extents will be in the same place and
not be overwritten by new metadata. This provides a mechanism to upgrade the metadata format or to
add/remove metadata areas. Use with care.

--setphysicalvolumesize Size[m|UNIT]
Overrides the automatically detected size of the PV. Use with care, or prior to reducing the
physical size of the device.

-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 hasn't.

-u|--uuid String
Specify a UUID for the device. Without this option, a random UUID is generated. This option is
needed before restoring a backup of LVM metadata onto a replacement device; see vgcfgrestore(8).
As such, use of --restorefile is compulsory unless the --norestorefile is used. All PVs must have
unique UUIDs, and LVM will prevent certain operations if multiple devices are seen with the same
UUID. See vgimportclone(8) for more information.

-v|--verbose ...
Set verbose level. Repeat from 1 to 4 times to increase the detail of messages sent to stdout and
stderr.

--version
Display version information.

-y|--yes
Do not prompt for confirmation interactively but always assume the answer yes. Use with extreme
caution. (For automatic no, see -qq.)

-Z|--zero y|n
Controls if the first 4 sectors (2048 bytes) of the device are wiped. The default is to wipe
these sectors unless either or both of --restorefile or --uuid are specified.

VARIABLES

       PV     Physical Volume name, a device path under /dev.  For commands  managing  physical  extents,  a  PV
              positional  arg  generally  accepts  a  suffix indicating a range (or multiple ranges) of physical
              extents (PEs). When the first PE is omitted, it defaults to the start of the device, and when  the
              last  PE is omitted it defaults to end.  Start and end range (inclusive): PV[:PE-PE]...  Start and
              length range (counting from 0): PV[:PE+PE]...

       String See the option description for information about the string content.

       Size[UNIT]
              Size is an input number that accepts an optional unit.  Input units are always treated as base two
              values, regardless of capitalization, e.g. 'k' and 'K' both refer to 1024.  The default input unit
              is specified by letter, followed by |UNIT.  UNIT represents other possible  input  units:  b|B  is
              bytes,  s|S  is  sectors of 512 bytes, k|K is KiB, m|M is MiB, g|G is GiB, t|T is TiB, p|P is PiB,
              e|E is EiB.  (This should not be confused with the output control --units, where  capital  letters
              mean multiple of 1000.)

ENVIRONMENT VARIABLES

       See  lvm(8)  for  information  about  environment  variables  used  by lvm.  For example, LVM_VG_NAME can
       generally be substituted for a required VG parameter.

EXAMPLES

       Initialize a partition and a full device.
       pvcreate /dev/sdc4 /dev/sde

       If a device is a 4 KiB sector drive that compensates for windows partitioning (sector  7  is  the  lowest
       aligned  logical  block,  the  4 KiB  sectors start at LBA -1, and consequently sector 63 is aligned on a
       4 KiB boundary) manually account for this when initializing for use by LVM.
       pvcreate --dataalignmentoffset 7s /dev/sdb