Delta update

This article relies excessively on references to primary sources. Please improve this article by adding secondary or tertiary sources.
Find sources: "Delta update" – news · newspapers · books · scholar · JSTOR (August 2022) (Learn how and when to remove this message)

|

Update that only requires the user to download changed code

A delta update is a software update that requires the user to download only those parts of the software's  code that are new, or have been changed from their previous state, in contrast to having to download the entire  program. The use of delta updates can save significant amounts of time and computing bandwidth. The name "delta" derives from the mathematical science use of the Greek letter delta, Δ or δ to denote change.[1]

## Uses

[edit]

### Linux

[edit]

Delta update in Fedora Linux

Fedora Linux has supported binary delta updates by default using the yum presto plugin since June 2009. This is based on RPM Package Manager's deltarpm system (2004), which was in turn based on bsdiff.[2] This functionality has been inherited by Fedora-derived operating systems, including RedHat Enterprise Linux and its variant, CentOS. From Fedora 40 onward, delta updates had been discontinued.[3] openSUSE also uses delta-rpm's with its zypper manager. This is still in use, and the standard solution for the openSUSE Leap distribution today. A more primitive system, the SUSE patchrpm, worked by replacing changed files.[4]

A similar system for the dpkg-APT package manager system of Debian is `debdelta` (2006); despite an apparent halt on the homepage, its package repository as well as the source code remains actively maintained.[5] `debdelta` is not installed by default and not many mirrors have been set up for it. A member of the developer team has proposed yet another format that integrates directly into the currently mirrored main repositories called patch debs in 2018. It is intended to have more integrity checks.[6]

A descendant of Debian, Ubuntu developers have tried many times to implement delta updates for their system. During 2006 they tried to create one, but were confronted with too many options and dropped the efforts.[7] In 2011 they tried to just set up `debdelta`, but once again dropped the efforts in May of the same year.[8]

The Arch Linux package manager pacman used to support a form of delta updating using VCDIFF (xdelta). It was scrapped due to an arbitrary command execution vulnerability (CVE-2019-18183) due to a lack of string escaping.[citation needed]

### Windows

[edit]

Windows Update has supported delta updates since Windows XP which are called express installation files. On redistributing updates, Windows Server Update Services has supported delta updates since Windows Server 2003.[9]

### FreeBSD

[edit]

FreeBSD has supported delta updates using portsnap[10] since November 2005.[11] Given FreeBSD's traditional stance of focusing on source code updates, no method of delta binary updates currently exists.

### Google

[edit]

Google refers to delta updates as "smart updates." This has been implemented in Google's Android operating system devices that run on Android 2.3 or above. Google engineers have estimated that smart updates would be only about one third the size of a full update on average.[citation needed]

Google's open source project Chromium requires frequent updates to narrow the window of vulnerability.[12] It uses a disassembly-based diffing algorithm called "courgette" to reduce diff size of two binary executable files, which reduces the diff patch from 6.7% (bsdiff) to 0.76% (bsdiff + courgette) for one version update.[13] The technology helped Chrome to push its updates to 100% of users in less than 10 days.

App APK updates in Android's Play Store use bsdiff since 2016, a new efficient delta update algorithm introduced in 2003.[14]

### Apple iOS

[edit]

Apple's iOS is also capable of delta updates for operating system[citation needed] and application updates to reduce bandwidth usage. [15]

## See also

[edit]

* Data differencing
* Delta encoding

## References

[edit]

1. ^ Mullin, Sean (2017-04-25). "What is Delta in Math?". Sciencing. Leaf Group Media. Retrieved 2022-09-06. "delta...means 'change' or 'the change in' in mathematics"
2. ^ "Fedora Features/Presto".
3. ^ "Changes/Drop Delta RPMs - Fedora Project Wiki". fedoraproject.org. Retrieved 2024-06-02.
4. ^ "6.3. RPM and Patches". www.pks.mpg.de. Archived from the original on 2020-03-24. Retrieved 2020-03-24.
5. ^ "debdelta at the Debian Project". (for source code, see debian "developer information" for package; for repository, see http://debdeltas.debian.net/debian-deltas/pool/.)
6. ^ "Teams/Dpkg/Spec/DeltaDebs". Debian Wiki.
7. ^ "SmallerUpdates". Ubuntu Wiki. Retrieved 13 January 2020.
8. ^ "UbuntuDebdeltaSupport".
9. ^ "Determine Bandwidth Options to Use for Your Deployment". 9 April 2014.
10. ^ "Secure FreeBSD ports tree updating".
11. ^ "FreeBSD 6.0-RELEASE Announcement".
12. ^ "Smaller is faster (and safer too)".
13. ^ "Software Updates: Courgette".
14. ^ Google Play’s new delta algorithm reduces size of Android app updates
15. ^ "Technical Q&A QA1779: Reducing Download Size for iOS App Updates". developer.apple.com. Retrieved 2015-07-07.

This installation software article is a stub. You can help Wikipedia by expanding it.

|

* v
* t
* e

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template