Jsummers: Category:Compression

2021-05-31T14:36:10Z

Category:Compression

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2020-11-02T00:13:04Z

Created page with "{{FormatInfo |formattype=electronic |subcat=File transfer |extensions={{ext|zck}} |released=2018<ref>https://www.jdieter.net/posts/2018/04/30/introducing-zchunk/ </ref> }} '''..."

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{{FormatInfo
|formattype=electronic
|subcat=File transfer
|extensions={{ext|zck}}
|released=2018<ref>https://www.jdieter.net/posts/2018/04/30/introducing-zchunk/ </ref>
}}
'''Zchunk''' is a format for compressing files in a way that is well-suited for synchronizing two copies of a file over a network; as well as a program that performs this syncronization. Arguably this problem was already solved by the older [[Rsync]] system, but due to the widespread adoption of [[HTTP]] for non-[[Web]] communications purposes, it cannot always be used. Zchunk first splits the file into a number of "chunks"; then compresses these chunks individually, so that, after a comparison has been made between the copies of the receiver and sender, only the changed chunks need to be downloaded. Unlike some similar formats, Zchunk concatenates all the chunks together, along with a header, into a single file.

Zchunk was developed in order to allow the [https://fedoraproject.org Fedora] Linux distribution to use less bandwidth when its software updater was downloading metadata.<ref>https://www.jdieter.net/posts/2018/05/31/what-is-zchunk/ → Background</ref>

[[Zstd]] compression is currently (2020) the only format supported; and Zchunk also supports an embedded [[PGP]] signature.

== Identification ==
Version 1 Zchunk files (as of 2020 the only version that exists) begin with {{magic|00 5A 43 4B 31}}.<ref>https://github.com/zchunk/zchunk/blob/master/zchunk_format.txt</ref>

== Specifications ==
* [https://github.com/zchunk/zchunk/blob/master/zchunk_format.txt zchunk_format.txt]

== Software ==
* [https://github.com/zchunk/zchunk Main implementation]

== Links ==
* [https://www.jdieter.net/posts/2018/04/30/introducing-zchunk/ Introducing zchunk]
* [https://www.jdieter.net/posts/2018/05/31/what-is-zchunk/ What is zchunk?]

== See Also ==
* [[Zstandard dictionary]] (Can be used by Zchunk)
* [[casync]]
* [[zsync]]

== References ==
<references />

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Zchunk - Revision history

Jsummers: Category:Compression

Effect2: Created page with "{{FormatInfo |formattype=electronic |subcat=File transfer |extensions={{ext|zck}} |released=2018https://www.jdieter.net/posts/2018/04/30/introducing-zchunk/ }} '''..."