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+//po4a: entry man manual
+////
+SPDX-License-Identifier: MIT
+
+Copyright (C) 2008 - 2012 Julian Andres Klode. See hardlink.c for license.
+Copyright (C) 2021 Karel Zak <kzak@redhat.com>
+////
+= hardlink(1)
+:doctype: manpage
+:man manual: User Commands
+:man source: util-linux {release-version}
+:page-layout: base
+:command: hardlink
+
+== NAME
+
+hardlink - link multiple copies of a file
+
+== SYNOPSIS
+
+*hardlink* [options] [_directory_|_file_]...
+
+== DESCRIPTION
+
+*hardlink* is a tool that replaces copies of a file with either hardlinks
+or copy-on-write clones, thus saving space.
+
+*hardlink* first creates a binary tree of file sizes and then compares
+the content of files that have the same size. There are two basic content
+comparison methods. The *memcmp* method directly reads data blocks from
+files and compares them. The other method is based on checksums (like SHA256);
+in this case for each data block a checksum is calculated by the Linux kernel
+crypto API, and this checksum is stored in userspace and used for file
+comparisons.
+
+For each file also an "intro" buffer (32 bytes) is cached. This buffer is used
+independently from the comparison method and requested cache-size and io-size.
+The "intro" buffer dramatically reduces operations with data content as files
+are very often different from the beginning.
+
+== OPTIONS
+
+include::man-common/help-version.adoc[]
+
+*-v*, *--verbose*::
+Verbose output, explain to the user what is being done. If specified once, every hardlinked file is displayed. If specified twice, it also shows every comparison.
+
+*-q*, *--quiet*::
+Quiet mode, don't print anything.
+
+*-n*, *--dry-run*::
+Do not act, just print what would happen.
+
+*-y*, *--method* _name_::
+Set the file content comparison method. The currently supported methods are
+sha256, sha1, crc32c and memcmp. The default is sha256, or memcmp if Linux
+Crypto API is not available. The methods based on checksums are implemented in
+zero-copy way, in this case file contents are not copied to the userspace and all
+calculation is done in kernel.
+
+*--reflink*[=_when_]::
+Create copy-on-write clones (aka reflinks) rather than hardlinks. The reflinked files
+share only on-disk data, but the file mode and owner can be different. It's recommended
+to use it with *--ignore-owner* and *--ignore-mode* options. This option implies
+*--skip-reflinks* to ignore already cloned files.
++
+The optional argument _when_ can be *never*, *always*, or *auto*. If the _when_ argument
+is omitted, it defaults to *auto*, in this case, *hardlink* checks filesystem type and
+uses reflinks on BTRFS and XFS only, and fallback to hardlinks when creating reflink is impossible.
+The argument *always* disables filesystem type detection and fallback to hardlinks, in this case,
+only reflinks are allowed.
+
+*--skip-reflinks*::
+Ignore already cloned files. This option may be used without *--reflink* when creating classic hardlinks.
+
+*-f*, *--respect-name*::
+Only try to link files with the same (base)name. It's strongly recommended to use long options rather than *-f* which is interpreted in a different way by other *hardlink* implementations.
+
+*-p*, *--ignore-mode*::
+Link and compare files even if their mode is different. Results may be slightly unpredictable.
+
+*-o*, *--ignore-owner*::
+Link and compare files even if their owner information (user and group) differs. Results may be unpredictable.
+
+*-t*, *--ignore-time*::
+Link and compare files even if their time of modification is different. This is usually a good choice.
+
+*-c* *--content*::
+Consider only file content, not attributes, when determining whether two files are equal. Same as *-pot*.
+
+*-X*, *--respect-xattrs*::
+Only try to link files with the same extended attributes.
+
+*-m*, *--maximize*::
+Among equal files, keep the file with the highest link count.
+
+*-M*, *--minimize*::
+Among equal files, keep the file with the lowest link count.
+
+*-O*, *--keep-oldest*::
+Among equal files, keep the oldest file (least recent modification time). By default, the newest file is kept. If *--maximize* or *--minimize* is specified, the link count has a higher precedence than the time of modification.
+
+*-x*, *--exclude* _regex_::
+A regular expression which excludes files from being compared and linked.
+
+*-i*, *--include* _regex_::
+A regular expression to include files. If the option *--exclude* has been given, this option re-includes files which would otherwise be excluded. If the option is used without *--exclude*, only files matched by the pattern are included.
+
+*-s*, *--minimum-size* _size_::
+The minimum size to consider. By default this is 1, so empty files will not be linked. The _size_ argument may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB").
+
+*-S*, *--maximum-size* _size_::
+The maximum size to consider. By default this is 0 and 0 has the special meaning of unlimited. The _size_ argument may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB").
+
+*-b*, *--io-size* _size_::
+The size of the *read*(2) or *sendfile*(2) buffer used when comparing file contents.
+The _size_ argument may be followed by the multiplicative suffixes KiB, MiB,
+etc.  The "iB" is optional, e.g., "K" has the same meaning as "KiB". The
+default is 8KiB for memcmp method and 1MiB for the other methods. The only
+memcmp method uses process memory for the buffer, other methods use zero-copy
+way and I/O operation is done in the kernel. The size may be altered on the fly
+to fit a number of cached content checksums.
+
+*-r*, *--cache-size* _size_::
+The size of the cache for content checksums. All non-memcmp methods calculate checksum for each
+file content block (see *--io-size*), these checksums are cached for the next comparison. The
+size is important for large files or a large sets of files of the same size. The default is
+10MiB.
+
+== ARGUMENTS
+
+*hardlink* takes one or more directories which will be searched for files to be linked.
+
+== BUGS
+
+The original *hardlink* implementation uses the option *-f* to force hardlinks creation between filesystem. This very rarely usable feature is no more supported by the current *hardlink*.
+
+*hardlink* assumes that the trees it operates on do not change during operation. If a tree does change, the result is undefined and potentially dangerous. For example, if a regular file is replaced by a device, *hardlink* may start reading from the device. If a component of a path is replaced by a symbolic link or file permissions change, security may be compromised. Do not run *hardlink* on a changing tree or on a tree controlled by another user.
+
+== AUTHOR
+
+There are multiple *hardlink* implementations. The very first implementation is from Jakub Jelinek for Fedora distribution, this implementation has been used in util-linux between versions v2.34 to v2.36. The current implementations is based on Debian version from Julian Andres Klode.
+
+include::man-common/bugreports.adoc[]
+
+include::man-common/footer.adoc[]
+
+ifdef::translation[]
+include::man-common/translation.adoc[]
+endif::[]