Resilient File System (ReFS)

Summary

The Resilient File System (ReFS) was introduced in Windows 8 server pre release, which became Windows 2012 server, and was added to Windows 8.1. ReFS is a new file system to the Windows NT platform. This specification is based on available documentation and was enhanced by analyzing test data.

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

Document information

Author(s):	Joachim Metz <joachim.metz@gmail.com>
Abstract:	This document contains information about the Resilient File System (ReFS)
Classification:	Public
Keywords:	ReFS, Resilient File System

License

Copyright (C) 2012-2023, 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	May 2012	Initial version.
0.0.2	J.B. Metz	September 2012	Additional information about format.
0.0.3	J.B. Metz	November 2013	Additional information about format.
0.0.4	J.B. Metz	June 2023	Switched to asciidoc format and additional information about format.
0.0.5	J.B. Metz	July 2023	Additional information about format.

1. Overview

The Resilient File System (ReFS) was introduced in Windows 8 server pre release, which became Windows 2012 server, and was added to Windows 8.1. ReFS is a new file system to the Windows NT platform.

A volume consists of:

a volume header
metadata blocks
- superblock
file and directory data
a copy of the volume header

Characteristics	Description
Byte order	little-endian
Date and time values	FILETIME in UTC
Character strings	ASCII strings are Single Byte Character (SBC) or Multi Byte Character (MBC) string stored with a codepage. Sometimes referred to as ANSI string representation. Though technically maybe incorrect, this document will use term (extended) ASCII string. Unicode strings are stored in UTF-16 little-endian without the byte order mark (BOM).

1.1. Versions

There are multiple version of ReFS.

ReFS version	Remarks
1.1	Used by Windows 8 (preview) and Windows Server 2012
1.2	Used by Windows 8.1, Windows 10 (1507 to 1607) and Windows Server 2012 R2

2.0	Used by Windows Server 2016 (preview)

2.2	Used by Windows 10 (preview)

3.0	Used by Windows Server 2016 (preview)
3.1	Used by Windows Server 2016
3.2	Used by Windows 10 (1703)
3.3	Used by Windows 10 (1709)
3.4	Used by Windows 10 (1803) and Windows server 2019
3.5	Used by Windows 11 (preview)
3.6	Used by Windows 11 (preview)
3.7	Used by Windows 11 and Windows server 2022

1.2. Test version

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

Windows 8
Windows 2012 Server R2
Windows 2016 Server
Windows 2019 Server

2. The volume header

The volume header is stored at the start of the volume. A copy of volume header is stored at the end of the volume.

Note	The size of the partition can be larger then the number of sectors in the volume.

The volume header is 512 bytes of size and consists of:

Offset	Size	Value	Description
File system recognition structure (FILE_SYSTEM_RECOGNITION_STRUCTURE)
0	3	0x00	Boot entry point (or JMP instruction)
3	8	"ReFS\x00\x00\x00\x00"	File system signature (or file system name)
11	5	0x00	Unknown (empty values)
16	4	"FSRS"	File system recognition structure identifier
20	2	0x200	Unknown (size of file system recognition structure?)
22	2		Unknown (checksum of file system recognition structure?)

24	8		Number of sectors
32	4		Sector size
36	4		Sectors per cluster block (allocation unit)
40	1		Major format version
41	1		Minor format version
42	2	0x00	Unknown (flags?)
44	4		Unknown
48	8	0x00	Unknown (empty values)
56	8		Volume serial number
64	8		Container (or band size)
72	440	0x00	Unknown (empty values)

Note	Note that currently 4096 and 65536 have been observed as supported cluster block (allocation unit) byte sizes.

Note	Note the container size has been first observed in format version 3.4, in previous format versions such as 3.1, which has containers, this value is 0.

3. Metadata

Metadata is stored in one or more blocks (or pages).

There are multiple levels of metadata:

Level	Block signature	Description
0	"SUPB"	Superblock
1	"CHKP"	Checkpoint
2+	"MSB+"	Ministore tree (B+-tree)

TODO: is the metadata block referred to as synchronous ministore (SMS) by Microsoft?

3.1. Metadata block header

3.1.1. Metadata block header - format version 1

The format version 1 metadata block header is 48 bytes of size and consists of:

Offset	Size	Value	Description
0	8		Block number The block number is relative from the start of the volume
8	8		Unknown (sequence number?)
16	8	0x00	Unknown (empty values)
24	8		Unknown
32	8	0x01	Unknown (flags or level?)
40	8	0x00	Unknown (empty values)

TODO: It seems that the data in bytes 8 – 23 is used as an identifier. Level 3 table contains an identifier that matches the data in the corresponding level 4 block.

3.1.2. Metadata block header - format version 3

The format version 3 metadata block header is 80 bytes of size and consists of:

Offset	Size	Value	Description
0	4		Signature
4	4	2	Unknown
8	4	0x00	Unknown (empty values)
12	4		Unknown (volume signature?)
16	8		Unknown (virtual allocator clock?)
24	8		Unknown (tree update clock?)
32	8		First block number
40	8		Second block number
48	8		Third block number
56	8		Fourth block number
64	8		Unknown (table identifier upper 64-bit?)
72	8		Unknown (table identifier lower 64-bit?)

Note	In format version 3 the metadata can span multiple metadata blocks.

3.2. Metadata block reference

3.2.1. Metadata block reference - format version 1

The format version 1 metadata block reference is 24 bytes of size and consists of:

Offset	Size	Value	Description
0	8		Block number
Checkum descriptor
8	2	0x00	Unknown (empty values)
10	1		Checksum type
11	1		Checksum data offset The offset is relative to the start of the checksum descriptor
12	2		Checksum data size
14	2	0x00	Unknown (empty values)
16	8		Checksum data

3.2.2. Metadata block reference - format version 3

The format version 3 metadata block reference is 48 bytes of size and consists of:

Offset	Size	Value	Description
0	8		First block number
8	8		Second block number
16	8		Third block number
24	8		Fourth block number
Checkum descriptor
32	2	0x00	Unknown (empty values)
34	1		Checksum type
35	1		Checksum data offset The offset is relative to the start of the checksum descriptor
36	2		Checksum data size
38	2	0x00	Unknown (empty values)
40	8		Checksum data

3.2.3. Checksum type

Value	Identifier	Description
1		CRC-32C (or CRC32-C), which uses the Castagnoli polynomial (0x1edc6f41)
2		CRC64-ECMA-182 Checksum data size is 8 bytes

4. Superblock (level 0) metadata

The superblock metadata consists of:

Metadata block header
Superblock
Checkpoint references data
Self metadata block reference

4.1. Superblock

The superblock is 48 bytes of size and consists of:

Offset	Size	Value	Description
0	16		Volume identifier
16	8	0x00	Unknown (empty values)
24	8		Unknown (sequence number?)
32	4		Checkpoint references data offset The offset is relative to the start of the metadata block
36	4	2	Unknown (number of checkpoint metadata block numbers?)
40	4		Self (block) reference data offset The offset is relative to the start of the metadata block
44	4		Self (block) reference data size

4.2. Checkpoint references data

The checkpoint references data is variable of size and consists of:

Offset	Size	Value	Description
0	number of entries x 8		Checkpoint metadata block number

5. Checkpoint (level 1) metadata

The checkpoint metadata consists of:

Metadata block header
Superblock
Checkpoint header
Checkpoint trailer
Self <<metadata_block_reference,metadata block reference>
Ministore tree metadata block references

5.1. Checkpoint header

The checkpoint header is 16 bytes of size and consists of:

Offset	Size	Value	Description
0	4	0x00	Unknown (empty values)
4	2		Major format version
6	2		Minor format version
8	4		Self (block) reference data offset The offset is relative to the start of the metadata block
12	4		Self (block) reference data size

5.2. Checkpoint trailer

5.2.1. Checkpoint trailer - format version 1

The format version 1 checkpoint trailer is variable of size and consists of:

Offset	Size	Value	Description
0	8		Unknown (sequence number?)
8	4		Unknown (checkpoint data size?)
12	4		Unknown (seen: 32)
16	8		Unknown
24	4		Number of offsets
28	number of offset x 4		Array of offsets The offset is relative to the start of the metadata block
…	…	0x00	Unknown (empty values)

5.2.2. Checkpoint trailer - format version 3

The format version 3 checkpoint trailer is variable of size and consists of:

Offset	Size	Value	Description
0	8		Unknown (sequence number or checkpoint clock?)
8	8		Unknown (virtual allocator clock?)
16	4		Unknown (oldest log record?)
20	4		Unknown
24	8		Unknown
32	8		Unknown
40	4		Unknown (checkpoint data size?)
44	4		Unknown (seen: 32)
48	4		Number of offsets
52	number of offset x 4		Array of offsets The offset is relative to the start of the metadata block
…	…	0x00	Unknown (empty values)

5.3. Ministore tree block references

Index	Identifier	Description
0		Objects tree
1		Medium allocator tree
2		Container allocator tree
3		Schema tree
4		Parent-child relationship tree
5		Copy of object tree
6		Block reference count tree
Seen in format version 3
7		Container tree
8		Copy of container tree
9		Copy of schema tree
10		Container index tree
11		Integrity state tree
12		Small allocator tree

6. Ministore tree (level 2+) metadata

The ministore tree metadata consists of:

Metadata block header
Node header offset
Optional tree header
Optional header data
Node header
Node records
Unused
Node record offsets

Note	Note that in format version 3 the upper 16-bit of the record offsets is set to 0xffff.

6.1. Node header offset

The node header offset is 4 bytes in size and consists of:

Offset	Size	Value	Description
0	4		Node header offset The offset is relative to the start of the node header offset

6.2. Tree header

The tree header is 36 bytes in size and consists of:

Offset	Size	Value	Description
0	2	40	Header data offset The offset is relative to the start of the node header offset
2	2		Unknown (seen: 0 or 1)
4	4		Unknown (seen: 0)
8	4		Unknown
12	4		Unknown
16	4		Unknown (seen: 2)
20	4		Unknown (number of branch nodes?)
24	4		Unknown
28	4		Unknown (number of leaf values?)
32	4		Unknown

6.3. Node header

The node header is 32 bytes of size and consists of:

Offset	Size	Description
0	4	Data area start offset The offset is relative to the start of the node header
4	4	Data area end offset The offset is relative to the start of the node header
8	4	Unused data size
12	1	Node level, where 0 is the level of the leaf values
13	1	Node type flags
14	2	Unknown (empty values)
16	4	Record offsets start offset The offset is relative to the start of the node information entry
20	4	Number of record offsets
24	4	Record offsets end offset The offset is relative to the start of the node information entry or 0 if not set
28	4	Unknown (empty values)

6.3.1. Node type flags

Value	Identifier	Description
0x01		Is branch (or inner) node
0x02		Is root node
0x04		Is stream node

6.4. Node record

The node record is variable of size and consists of:

Offset	Size	Description
0	4	Node record size Includes the 4 bytes of the size value
4	2	Key data offset The offset is relative to the start of the node record
6	2	Key data size
8	2	Flags See section: Node record flags
10	2	Value data offset The offset is relative to the start of the node record
12	2	Value data size

6.4.1. Node record flags

Value	Identifier	Description
0x0002		Unknown (No key data?)
0x0004		Unknown (Is unallocated (free)?)
0x0008		Value data contains an embedded Ministore node

0x0040		Unknown (Is stream record?)

6.4.2. Branch node record

The key of a branch node contains key of the largest value of the corresponding branch. Note that the key of the last branch node can be empty.

The value of a branch node contains a metadata block reference of the corresponding sub node.

7. Objects tree

The objects tree is a Ministore B+-tree that contains object records.

7.1. Object record

An object record consists of:

key, containing an object identifier
value, containing a metadata block reference that reference the corresponding object Ministore B+-tree

7.1.1. Object record key

The object record key is 16 bytes in size and consists of:

Offset	Size	Value	Description
0	8		Record key (upper 64-bits), which contains 0-byte values
8	8		Record key (lower 64-bits), which contains an object identifier

Note	Note that the record key corresponds to the file system identifier.

7.1.2. Object record value - format version 1

The format version 1 object record value is 48 bytes in size and consists of:

Offset	Size	Description
0	24	Block reference See section: metadata block reference
24	8	Unknown
32	4	Unknown
36	4	Unknown
40	8	Unknown (related object identifier?)

Object record value - format version 3

The format version 3 object record value is variable in size and consists of:

Offset	Size	Description
0	8	Unknown
8	4	Unknown
12	4	Unknown (size of block reference data?)
16	4	Unknown (size of used record data?)
20	4	Unknown
24	4	Unknown
28	4	Unknown
32	48	Block reference See section: metadata block reference
…	…	Unknown (remnant data?)

Object identifiers

Value	Identifier	Description
0x00000007		Upcase object Introduced in format version 3?
0x00000008		Copy of Upcase object Introduced in format version 3?
0x00000009		Logfile information object Introduced in format version 3?
0x0000000a		Copy of logfile information object Introduced in format version 3?

0x0000000d		Trash stream object Introduced in format version 3?

0x00000500		Volume information object
0x00000501		Copy of volume information object Introduced in format version 3?

0x00000520		File system information object

0x00000530

0x00000540		+ Introduced in format version 3?
0x00000541		+ Introduced in format version 3?

0x00000600	REFS_ROOT_DIRECTORY_ID	Root directory object

0x00000701	REFS_OBJECT_UNKNOWN_3	Directory object Values 0x00000701 and above are used for sub directories.

8. Container tree

The container tree is a Ministore B+-tree that contains container records.

Note	Note that the container tree has only been observed with format version 3.

8.1. Container record

A container record consists of:

key, containing the container (or band) identifier
value, containing information about the container

8.1.1. Container record key

The container record key is the first 16 bytes of the container record value.

8.1.2. Container record value

The container record value is 160 bytes in size and consists of:

Offset	Size	Description
0	8	Container (or band) identifier
8	4	Unknown
12	4	Unknown
16	4	Unknown (flags?)
20	4	Unknown
24	8	Unknown
32	8	Unknown (number of unused cluster blocks?)
40	8	Unknown
48	28	Unknown (empty values)
76	4	Unknown
80	64	Unknown (empty values)
144	8	Cluster block number
152	8	Cluster size Contains the number of (cluster) blocks

9. Directory object

The directory object is a Ministore B+-tree that contains multiple directory records.

The format of the directory record value is dependent on the record type in the directory record key.

A ReFS file system identifier consists of:

64-bit file identifier or 0 for the directory
64-bit directory object identifier

9.1. Directory record key

The directory record key is variable in size and consists of:

Offset	Size	Value	Description
0	2		Record type
2	…		Data

9.1.1. Record types

Value	Identifier	Description
0x0010		Base record
0x0020		Name record
0x0030		Entry record

9.1.2. Base record (record type: 0x0010)

The directory object base record key is 4 bytes in size and consists of:

Offset	Size	Value	Description
0	2	0x0010	Record type
2	2		Unknown (seen: 0x0000)

9.1.3. Name record (record type: 0x0020)

The directory object name record key is 24 bytes in size and consists of:

Offset	Size	Value	Description
0	2	0x0020	Record type
2	2		Unknown (seen: 0x8000)
4	4		Unknown (empty values?)
8	8		File system identifier (lower 64-bits)
16	8		File system identifier (upper 64-bits)

The directory object name record value is variable in size and consists of:

Offset	Size	Description
0	8	Unknown (empty values?)
8	2	Unknown (seen: 0x0c)
10	…	Name Contains an UTF-16 little-endian without end-of-string character

Note	The name string is not strict UTF-16 since it allows for unpaired surrogates, such as "U+d800" and "U+dc00".

9.1.4. Entry record (record type: 0x0030)

The directory object entry record key is variable in size and consists of:

Offset	Size	Value	Description
0	2	0x0030	Record type
2	2		Directory entry type See section: Directory entry types
4	…		Name Contains an UTF-16 little-endian without end-of-string character

Note	The name string is not strict UTF-16 since it allows for unpaired surrogates, such as "U+d800" and "U+dc00".

The format of the directory object entry record value is dependent on the directory entry type.

9.1.5. Directory entry types

Value	Identifier	Description
0		File system metadata file
1		File See section: Directory object entry record file values
2		Directory See section: Directory object entry record directory values

9.2. Directory object entry record directory values

The directory object entry record directory values are 72 bytes in size and consist of:

Offset	Size	Description
0	8	Directory object identifier See section: object identifiers
8	8	Unknown (part of the object identifier?)
16	8	Creation date and time Contains a FILETIME
24	8	Last modification date and time (Also referred to as last written date and time) Contains a FILETIME
32	8	Entry (or metadata) last modification date and time Contains a FILETIME
40	8	Last access date and time Contains a FILETIME
48	16	Unknown (empty values)
64	4	File attribute flags
68	4	Unknown (empty values)

9.3. Directory object entry record file values

The directory object entry record file values are variable in size and consist of an embedded Ministore node. The embedded Ministore node contains:

header data
one or more attribute records

Note	Note that although the Ministore node is embedded in the record value it can branch out to other Ministore nodes stored elsewhere.

The header data is 128 bytes in size and consists of:

Offset	Size	Description
0	8	Creation date and time Contains a FILETIME
8	8	Last modification date and time (Also referred to as last written date and time) Contains a FILETIME
16	8	Entry (or metadata) last modification date and time Contains a FILETIME
24	8	Last access date and time Contains a FILETIME
32	4	File attribute flags
36	4	Unknown
40	8	File system identifier (lower 64-bits)
48	8	File system identifier (upper 64-bits)
56	4	Unknown
60	4	Unknown
64	8	Data size
72	8	Allocated (or reserved) data size
80	32	Unknown
112	8	Unknown
120	8	Unknown

9.4. Attribute record

key data of default (or nameless) data attribute

00000000: 60 01 00 00 00 00 00 00  80 00 00 00 00 00         `....... ......

key data of alternate data attribute

00000000: 4a 00 00 00 00 00 00 00  b0 00 00 00 6d 00 79 00   J....... ....m.y.
00000010: 61 00 64 00 73 00                                  a.d.s.

Offset	Size	Description
0	8	Unknown
8	4	Unknown (attribute type)
12	…	Attribute name string Contains an UTF-16 little-endian without end-of-string character or an end-of-string character if the attribute is nameless

Value	Identifier	Description
0x10	$STANDARD_INFORMATION
0x30	$FILENAME
0x38	$DIR_LINK
0x40	$OBJECT_ID
0x50	$OBSOLETE
0x60	$VOLUME_NAME
0x70	$VOLUME_INFO
0x80	$DATA
0x90	$INDEX_ROOT
0xa0	$INDEX_ALLOCATION
0xb0	$NAMED_DATA
0xc0	$REPARSE_POINT
0xd0	$EA_INFORMATION
0xe0	$EA

9.4.1. Directory object entry record resident attribute

The directory object entry record resident attribute is variable in size and consists of:

Offset	Size	Description
0	4	Unknown (seen: 0 resident?)
4	4	(Resident or inline) data offset The offset is relative to the start of the record value
8	4	(Resident or inline) data size
12	4	Unknown
16	8	Unknown
24	8	Unknown
32	8	Unknown
40	8	Unknown
32	8	Unknown
40	4	Unknown
44	…	(Resident or inline) data

9.4.2. Directory object entry record non-resident attribute

The directory object entry record non-resident attribute is variable in size and consist of an embedded Ministore node. The embedded Ministore node contains:

header data
zero or more data run records

The header data is 96 bytes in size and consists of:

Offset	Size	Description
0	4	Unknown (seen: 1 non-resident?)
4	8	Unknown (empty values?)
12	8	Allocated (or reserved) data size
20	8	Data size
28	8	Valid data size
36	60	Unknown (empty values?)

9.5. Data run record

The directory object entry record data run record key is the first 16 bytes of the directory object entry record data run record value.

The directory object entry record data run record value is 16 bytes in size and consists of:

Offset	Size	Description
0	8	Data run logical offset
8	8	Data run size Contains the number of metadata blocks
16	8	Data run physical offset Contains a metadata block number
24	8	Unknown

10. File system information object

The file system information object is a Ministore B+-tree that contains a single file system information record.

10.1. File system information record key

The file system information record key is variable in size and consists of:

Offset	Size	Value	Description
0	2	0x30	Unknown
2	2	0x01	Unknown
4	…	"Volume Direct IO File"	String Contains an UTF-16 little-endian without end-of-string character

10.2. File system information record value

The file system record value is TODO bytes in size and consists of:

Offset	Size	Value	Description

TODO: describe

11. Volume information object

The volume information object is a Ministore B+-tree that contains multiple volume information records.

11.1. Volume information record key

The volume information record key is 8 bytes in size and consists of:

Offset	Size	Value	Description
0	8		Object identifier See section: object identifiers

Value	Identifier	Description
0x00000510		Volume name record Comparable to NTFS volume name attribute ($VOLUME_NAME)

0x00000520		TODO: describe

0x00000530		TODO: describe

0x00000540		TODO: describe

11.2. Volume name record value

The volume name record value is variable in size and consists of:

Offset	Size	Value	Description
0	…		Volume name Contains an UTF-16 little-endian without end-of-string character

Appendix A: References

[BALLENTHIN12]

Title:	The Microsoft ReFS On-Disk Layout
Author(s):	Willi Ballenthin
Date:	2012
URL:	http://www.williballenthin.com/forensics/refs/index.html

[GREEN13]

Title:	Resilient File System (ReFS) - Analysis of the File System found on Windows Server 2012 and Windows 8.1
Author(s):	Paul K. Green
Version:	0.6
Date:	September 2013
URL:	https://docs.google.com/uc?export=download&id=0B7_P1Njdyx3hdnNtYlpVZ2taaU0

[PRADE19]

Title:	Forensic Analysis of the Resilient File System (ReFS) Version 3.4
Author(s):	Paul Prade, Tobias Groß, Andreas Dewald
Date:	December 2019
URL:	https://www.sciencedirect.com/science/article/pii/S266628172030010X

[MSDN]

Title:	http://www.williballenthin.com/forensics/refs/index.html
URL:	http://blogs.msdn.com/b/b8/archive/2012/01/16/building-the-next-generation-file-system-for-windows-refs.aspx

Title:	FILE_SYSTEM_RECOGNITION_STRUCTURE structure
URL:	https://learn.microsoft.com/en-us/windows/win32/fileio/file-system-recognition-structure

[WIKIPEDIA]

Title:	Wikipedia: ReFS
URL:	https://en.wikipedia.org/wiki/ReFS

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.

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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.

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