LVM format specification

Summary

The Logical Volume Manager (LVM) is a volume manager for Linux, although the term is used for other Unix implementations as well. This specification is based on publicly available work on the format and was enhanced by analyzing test data.

This document is intended as a working document of the data format specification for the libvslvm project.

Document information

Author(s):	Joachim Metz <joachim.metz@gmail.com>
Abstract:	This document contains information about Logical Volume Manager (LVM) format.
Classification:	Public
Keywords:	Logical Volume Manager, LVM

License

Copyright (C) 2013-2020, Joachim Metz <joachim.metz@gmail.com>.
Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included
in the section entitled "GNU Free Documentation License".

Revision history

Version	Author	Date	Comments
0.0.1	J.B. Metz	July 2013	Initial version.
0.0.2	J.B. Metz	February 2014	Additional information.
0.0.3	J.B. Metz	July 2014	Additional information.
0.0.4	J.B. Metz	November 2014	Switched to asccidoc format.
0.0.5	J.B. Metz	January 2016	Additional information.
0.0.6	J.B. Metz	February 2018	Removed trailing whitespace.
0.0.7	J.B. Metz	December 2020	Format changes and additional information with thanks to B. Veigel.

1. Overview

The Logical Volume Manager (LVM) is a volume manager for Linux, although the term is used for other Unix implementations as well.

1.1. Terminology

Term	Description
logical extent (LE)	An extent (data range) that makes up the logical volume.
logical volume (LV)	A volume within the LVM, equivalent to a disk partition in e.g. the MBR or GPT volume system.
physical extent (PE)	An extent (data range) that makes up the physical volume.
physical volume (PV)	Typically a physical volume is a hard disk, though it may well just be a device that 'looks' like a hard disk (e.g. a software RAID device).
volume group (VG)	A collection of Logical Volumes and Physical Volumes.

1.2. Layout

An LVM volume consist of:

Volume group
Physical volumes
Logical volumes

An Physical volume consist of:

Empty sector
The physical volume label header
- The physical volume header
  - data area descriptor list
  - metadata area descriptor list
The metadata area
Data area (or data extents)

Characteristics	Description
Byte order	little-endian
Date and time values	POSIX timestamp in local timezone and/or ctime date and time string
Character strings	ASCII string with an end-of-string character

1.3. Test version

The following version of programs were used to test the information within this document:

lvm2

2. Physical volume label

The physical volume label is stored in the second sector of the physical volume. The physical volume label is currently 512 bytes of size and consists of:

physical volume label header
physical volume header

Note	According to [REDHAT] the physical volume label can be stored in any of the first four sectors.

2.1. Physical volume label header

The physical volume label header (struct label_header) is 32 bytes in size and consist of:

Offset	Size	Value	Description
0	8	"LABELONE"	Signature (or identifier)
8	8		Sector number The sector number of the physical volume label header
16	4		Checksum CRC-32 for offset 20 to end of the physical volume label sector
20	4		Data offset (or header size) The offset, in bytes, relative from the start of the physical volume label header
24	8	"LVM2\x20001"	Type indicator

The checksum is calculated using weak CRC-32 (CRC without XOR with 0xffffffff) using the polynominal 0xedb88320 and initial value 0xf597a6cf.

2.2. Physical volume header

The physical volume header (struct pv_header) is variable in size and consist of:

Offset	Size	Description
0	32	Physical volume identifier Contains a UUID stored as an ASCII string.
32	8	Physical volume size Value in bytes
40	…	List of data area descriptors The last descriptor in the list is terminator and consists of 0-byte values. See section: Data area descriptor
…	…	List of metadata area descriptors The last descriptor in the list is terminator and consists of 0-byte values. See section: Data area descriptor

The physical volume identifier can be used to uniquely identify a physical volume. The physical volume identifier is stored as: 9LBcEB7PQTGIlLI0KxrtzrynjuSL983W but is equivalent to its formatted variant: 9LBcEB-7PQT-GIlL-I0Kx-rtzr-ynju-SL983W, which is used in the metadata.

Note	The data area size can be 0. Does this represent all remaining available space?

2.2.1. Data area descriptor

Offset	Size	Value	Description
0	8		Data area offset The offset, in bytes, relative from the start of the physical volume
8	8		Data area size Value in bytes

3. The metadata area

The metadata area consist of:

Metadata area header
Metadata

According to [REDHAT] the metadata area is a circular buffer. New metadata is appended to the old metadata and then the pointer to the start of it is updated. The metadata area, therefore, can contain copies of older versions of the metadata.

3.1. Metadata area header

The metadata area header (struct mda_header) is 512 bytes in size and consist of:

Offset	Size	Value	Description
0	4		Checksum CRC-32 for offset 4 to end of the metadata area header
4	16	"\x20LVM2\x20x[5A%r0N*>"	Signature
20	4	1	Version
24	8		Metadata area offset Value in bytes The offset, in bytes, of the metadata area relative from the start of the physical volume
32	8		Metadata area size The size of the metadata area in bytes
40	4 x 24 = 96		List of raw location descriptors The last descriptor in the list is terminator and consists of 0-byte values. See section: Raw location descriptor
136	376	0	Unknown (unused)

The checksum is calculated using weak CRC-32 (CRC without XOR with 0xffffffff) using the polynominal 0xedb88320 and initial value 0xf597a6cf.

3.1.1. Raw location descriptor

The raw location descriptor (struct raw_locn) is 24 bytes in size and consist of:

Offset	Size	Description
0	8	Data area offset The offset, in bytes, relative from the start of the metadata area
8	8	Data area size Value in bytes
16	4	Checksum CRC-32 of the data area described by the raw location descriptor
20	4	Flags See section: Raw location descriptor flags

The checksum is calculated using weak CRC-32 (CRC without XOR with 0xffffffff) using the polynominal 0xedb88320 and initial value 0xf597a6cf.

Note	The data area size can be 0. It is assumed it represents the remaining available data.

3.1.2. Raw location descriptor flags

Value	Identifier	Description
0x00000001	RAW_LOCN_IGNORED	The raw location descriptor should be ignored.

4. Metadata

The metadata consist of:

Volume group main section
- Physical volumes sub section
  - Physical volume sub sections
- Logical volumes sub section
  - Logical volume sub sections
    
    Segment sub section
Global parameters

According to [REDHAT] by default, an identical copy of the metadata is maintained in every metadata area in every physical volume within the volume group. The metadata is stored as ASCII.

The metadata can also be stored in a stand-alone file.

4.1. Parameter definitions

The metadata sections are textual and use the following parameter definitions.

A parameter is defined as:

<identifier> = <value>

Where <identifier> contains a unique name of the parameter and <value> is one of the following types:

Value	Description
[0-9]+	An integer
"…"	A string
["…", "…", …]	A list (or array) of strings

Note	White space like space and new line characters seem to be ignored.

The # character is used for comments. A comment continues to the end-of-line.

Note	For now it is assumed that the # character is not allowed to be used in any of the values.

4.2. Volume group main section

The volume group main section is defined as:

<name> {
<parameters>
<sub sections>
}

Where:

<name> contains the name of the volume group.
<parameters> contains one of the following parameters:

Note can there be more than 1 volume group?

Value	Description
id	Volume group identifier (VG UUID) Contains an ASCII string in the following format: fg1fKZ-xoHz-CfAD-yQPx-l2HL-Y7kA-9kJ9LD
seqno	Metadata sequence number
status	The status flags Contains a list of strings. See section: Status flags
flags	The flags Contains a list of strings. See section: Flags
extent_size	The size of an extent The value contains the number of sectors According to `[REDHAT]` the sector size should be 512 bytes
max_lv	Maximum number of logical volumes
max_pv	Maximum number of physical volumes
metadata_copies	The number of metadata copies?

<sub sections> contains one of the following sub sections:

Value	Description
physical_volumes	The physical volumes sub sections
logical_volumes	The logical volumes sub sections

4.3. Physical volumes sub section

The physical volumes sub section is defined as:

physical_volumes {
<sub sections>
}

Where:

<sub sections> contains one of the following sub sections:

Value	Description
pv#	Individual physical volume sub section Where # is a place holder for a the physical volume number e.g. pv0. 0 appears to be the first number that is used.

4.4. Physical volume sub section

Each physical volume sub section is defined as:

pv# {
<parameters>
}

Where:

# is a place holder for a the physical volume number e.g. pv0
<parameters> contains one of the following parameters:

Value	Description
id	Physical volume identifier (PV UUID) Contains an ASCII string in the following format: 9LBcEB-7PQT-GIlL-I0Kx-rtzr-ynju-SL983W
device	The device filename Contains an ASCII string e.g. /dev/dm-0
status	The status flags Contains a list of strings. See section: Status flags
dev_size	The physical volume size including non-usable space The value contains the number of sectors According to `[REDHAT]` the sector size should be 512 bytes
pe_start	The start extent Ths start extent of the physical volume, contains an offset relative to the start of the physical volume
pe_count	The number of (allocated) extents in the physical volume

4.5. Logical volumes sub section

The logical volumes sub section is defined as:

logical_volumes {
<sub sections>
}

Where:

<sub sections> contains one of the following sub sections:

Value	Description
<name>	Individual physical volume sub section Where <name> is a place holder for a the logical volume name

4.6. Logical volume sub section

Each logical volume sub section is defined as:

<name> {
<parameters>
<sub sections>
}

Where:

<name> contains the name of the physical volume

Some implementations use lv_ as the prefix for a logical volume note that the format does not imply this convention.

<parameters> contains one of the following parameters:

Value	Description
id	Physical volume identifier (PV UUID) Contains an ASCII string in the following format: 9LBcEB-7PQT-GIlL-I0Kx-rtzr-ynju-SL983W
status	The status flags Contains a list of strings. See section: Status flags
flags	The flags Contains a list of strings. See section: Flags
segment_count	The number of segment sub sections

<sub sections> contains one of the following sub sections:

Value	Description
segment#	Individual physical volume sub section Where # is a place holder for the segment number e.g. segment1. 1 appears to be the first number that is used.

4.7. Segment sub section

Each segment sub section is defined as:

segment# {
<parameters>
}

Where:

# is a place holder for the segment number e.g. segment1
<parameters> contains one of the following parameters:

Value	Description
start_extent	The start extent of the segment The value contains the number of extents The number is relative to the start of the segment
extent_count	The number of extents in the segment (or current logical extent)
type	The segment type See section: Segment types
stripe_count	The number of stripes in the segment 1 ⇒ linear multiple stripes for different "RAID" variants?
stripes	The stripes list

4.8. Segment types

Value	Description
cache
cache-pool
error
free
linear
mirror
raid0
raid0_meta
raid1
raid10
raid10_near
raid4
raid5
raid5_la
raid5_ls
raid5_n
raid5_ra
raid5_rs
raid6
raid6_la_6
raid6_n_6
raid6_nc
raid6_nr
raid6_ra_6
raid6_rs_6
raid6_zr
snapshot
striped	Is striped
thin
thin-pool
vdo
vdo-pool
writecache
zero

Note	This list can be retrieved using `lvm segtypes`.

4.9. Stripes list

stripes = [
<physical volume name>, <start extent number>
]

Where:

<physical volume name> is a string containing the physical volume name e.g. "pv0".
<start extent number> the segment start extent number relative from the start of the data area.

start extent offset = ( start extent number x extent size x sector size ) + physical volume data area start offset

4.10. Global parameters

Value	Description
contents	The contents of the metadata area A string containing "Text Format Volume Group"
version	The metadata area version A numeric value containing 1
description	Description of the metadata area?
creation_host	The hostname of the system on which metadata area was created Can have a trailing comment that contains the output equivalent to "uname -a".
creation_time	The creation time of the metadata area Contains a numeric value of the number of seconds since January 1, 1970 00:00:00 UTC. Can have a trailing comment that contains the creation time as a ctime (function) string in UTC.

4.11. Status flags

Value	Description
ALLOCATABLE	Is allocatable [physical volume only]
RESIZEABLE	Can be re-sized [volume group only]
READ	Can be read
VISIBLE	Is visible [logical volume only]
WRITE	Can be written

4.12. Flags

Value	Description
	TODO

4.13. Comments

Some of the comment in the metadata can be interesting for forensic analysis e.g. the version of LVM used.

# Generated by LVM2 version 2.02.39 (2008-06-27): Sat Jan 17 11:45:29 2009

5. Notes

5.1. Tools

vgdisplay
pvdisplay
lvdisplay

5.2. Mapping modes

http://www.tldp.org/HOWTO/LVM-HOWTO/mapmode.html

5.3. Snapshots

http://www.tldp.org/HOWTO/LVM-HOWTO/snapshotintro.html

5.4. Metadata

1 sector: metadata area header – pointer to metadata
circular buffer, text format (at least 2 versions of metadata)
atomic update – 1) write new version 2) update pointer
SEQNO – sequential number
checksum, redundancy, autorepair

5.5. Metadata sample

# Generated by LVM2: Tue Jan 30 16:28:15 2007

contents = "Text Format Volume Group"
version = 1

description = "Created *before* executing 'lvextend -L+5G /dev/myvg/mylv /dev/sdc'"

creation_host = "tng3-1"  # Linux tng3-1 2.6.18-8.el5 #1 SMP Fri Jan 26 14:15:21 EST 2007 i686
creation_time = 1170196095  # Tue Jan 30 16:28:15 2007

myvg {
  id = "0zd3UT-wbYT-lDHq-lMPs-EjoE-0o18-wL28X4"
  seqno = 3
  status = ["RESIZEABLE", "READ", "WRITE"]
  extent_size = 8192    # 4 Megabytes
  max_lv = 0
  max_pv = 0

  physical_volumes {

    pv0 {
      id = "ZBW5qW-dXF2-0bGw-ZCad-2RlV-phwu-1c1RFt"
      device = "/dev/sda"   # Hint only

      status = ["ALLOCATABLE"]
      dev_size = 35964301   # 17.1491 Gigabytes
      pe_start = 384
      pe_count = 4390 # 17.1484 Gigabytes
    }

    pv1 {
      id = "ZHEZJW-MR64-D3QM-Rv7V-Hxsa-zU24-wztY19"
      device = "/dev/sdb"   # Hint only

      status = ["ALLOCATABLE"]
      dev_size = 35964301   # 17.1491 Gigabytes
      pe_start = 384
      pe_count = 4390 # 17.1484 Gigabytes
    }

    pv2 {
      id = "wCoG4p-55Ui-9tbp-VTEA-jO6s-RAVx-UREW0G"
      device = "/dev/sdc"   # Hint only

      status = ["ALLOCATABLE"]
      dev_size = 35964301   # 17.1491 Gigabytes
      pe_start = 384
      pe_count = 4390 # 17.1484 Gigabytes
    }

    pv3 {
      id = "hGlUwi-zsBg-39FF-do88-pHxY-8XA2-9WKIiA"
      device = "/dev/sdd"   # Hint only

      status = ["ALLOCATABLE"]
      dev_size = 35964301   # 17.1491 Gigabytes
      pe_start = 384
      pe_count = 4390 # 17.1484 Gigabytes
    }
  }
  logical_volumes {

    mylv {
      id = "GhUYSF-qVM3-rzQo-a6D2-o0aV-LQet-Ur9OF9"
      status = ["READ", "WRITE", "VISIBLE"]
      segment_count = 2

      segment1 {
        start_extent = 0
        extent_count = 1280   # 5 Gigabytes

        type = "striped"
        stripe_count = 1  # linear

        stripes = [
          "pv0", 0
        ]
      }
      segment2 {
        start_extent = 1280
        extent_count = 1280   # 5 Gigabytes

        type = "striped"
        stripe_count = 1  # linear

        stripes = [
          "pv1", 0
        ]
      }
    }
  }
}

5.6. Building a test file

dd if=/dev/zero of=image.raw bs=512 count=$(( 256 * 1024 * 2 ))

sudo losetup /dev/loop1 image.raw

sudo pvcreate /dev/loop1

sudo vgcreate vg_test /dev/loop1

sudo lvcreate -L 75M --name lv_test1 vg_test

sudo losetup -d /dev/loop1

Appendix A: References

Title:	LVM-HOWTO
URL:	http://www.tldp.org/HOWTO/LVM-HOWTO/mapmode.html

Title:	LVM1 source code
URL:	ftp://sources.redhat.com/pub/lvm/current/

Title:	LVM2 source code
URL:	ftp://sources.redhat.com/pub/lvm2/

[BROZ09]

Title:	LVM2 – data recovery
Author(s):	Milan Brož
Date:	2009
URL:	http://lvb.sti.fce.vutbr.cz/public/LinuxAlt_2009/2009_11_08_LA_04_LVM/2009_11_08_LA_04_LVM.pdf

[PVDISSECT]

Title:	pvdissect
URL:	https://wiki.syslinux.org/wiki/index.php?title=Development/LVM_support/pvdissect

[REDHAT]

Title:	Appendix D. LVM Volume Group Metadata
Date:	January 31, 2013
URL:	https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Logical_Volume_Manager_Administration/lvm_metadata.html

Appendix B: GNU Free Documentation License

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not "Transparent" is called "Opaque".

Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

The "publisher" means any person or entity that distributes copies of the Document to the public.

A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this definition.

The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
State on the Title page the name of the publisher of the Modified Version, as the publisher.
Preserve all the copyright notices of the Document.
Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
Include an unaltered copy of this License.
Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.
Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.
Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements".

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A "Massive Multiauthor Collaboration" (or "MMC") contained in the site means any set of copyrightable works thus published on the MMC site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or in part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

Files

Logical Volume Manager (LVM) format.asciidoc

Latest commit

History

Logical Volume Manager (LVM) format.asciidoc

File metadata and controls

LVM format specification

Summary

Document information

License

Revision history

1. Overview

1.1. Terminology

1.2. Layout

1.3. Test version

2. Physical volume label

2.1. Physical volume label header

2.2. Physical volume header

2.2.1. Data area descriptor

3. The metadata area

3.1. Metadata area header

3.1.1. Raw location descriptor

3.1.2. Raw location descriptor flags

4. Metadata

4.1. Parameter definitions

4.2. Volume group main section

4.3. Physical volumes sub section

4.4. Physical volume sub section

4.5. Logical volumes sub section

4.6. Logical volume sub section

4.7. Segment sub section

4.8. Segment types

4.9. Stripes list

4.10. Global parameters

4.11. Status flags

4.12. Flags

4.13. Comments

5. Notes

5.1. Tools

5.2. Mapping modes

5.3. Snapshots

5.4. Metadata

5.5. Metadata sample

5.6. Building a test file

Appendix A: References

Appendix B: GNU Free Documentation License

0. PREAMBLE

1. APPLICABILITY AND DEFINITIONS

2. VERBATIM COPYING

3. COPYING IN QUANTITY

4. MODIFICATIONS

5. COMBINING DOCUMENTS

6. COLLECTIONS OF DOCUMENTS

7. AGGREGATION WITH INDEPENDENT WORKS

8. TRANSLATION

9. TERMINATION

10. FUTURE REVISIONS OF THIS LICENSE

11. RELICENSING