Editing Booting (section)

===Bootloop===
[[File:TL-WR1043-ND V1 Serial Console.jpg|thumb|right|[[UART]] console of a [[TP-Link]] router with [[OpenWrt]] that is stuck in a bootloop]]

When [[debugging]] a concurrent and distributed [[system of systems]], a '''bootloop''' (also written '''boot loop''' or '''boot-loop''') is a diagnostic condition of an [[#Detection of an erroneous state|erroneous state]] that occurs on computing devices; when those devices repeatedly fail to complete the booting process and [[Reboot|restart]] before a boot sequence is finished,  a restart might prevent a user from accessing the regular interface.

{{quote|As the complexity of today's products increases, single projects, single departments or even single companies can no longer develop total products, causing concurrent and distributed development. Today and worldwide, industries are facing complex product development and its vast array of associated problems, relating to project organization, project control and product quality. Many processes will become distributed as well. The defect detection process, so important for measuring and eventually achieving product quality, is typically one of the first to experience problems caused by the distributed nature of the project. The distribution of defect detection activities over several parties introduces risks like the inadequate review of work products, occurrence of "blind spots" with respect to test coverage or over-testing of components. Lifecycle-wide coordination of defect detection is therefore needed to ensure effectiveness and efficiency of defect detection activities. —J.J.M. Trienekens; R.J. Kusters. (2004)<ref name=2004DefectDetection >{{cite conference |author1=J.J.M. Trienekens |author2=R.J. Kusters |url=https://ieeexplore.ieee.org/document/1372126 |date=19–21 September 2003 |title=Workshop: defect detection in distributed software development |conference=Eleventh Annual International Workshop on Software Technology and Engineering Practice |doi=10.1109/STEP.2003.40}}</ref>}}

====Detection of an erroneous state====
The system might exhibit its erroneous state in, for example, an explicit bootloop or a [[blue screen of death]], before recovery is indicated.<ref name=23JulReview /> Detection of an erroneous state may require a [[Apache Kafka|distributed event store and stream-processing platform]] for real-time operation of a distributed system.

====Recovery from an erroneous state====
An erroneous state can trigger bootloops; this state can be caused by misconfiguration from previously known-good operations. Recovery attempts from that erroneous state then enter a reboot, in an attempt to return to a known-good state. In Windows OS operations, for example, the recovery procedure was to reboot three times, the reboots needed to return to a usable menu.<ref name=1pctOfWindows>{{cite web |author=Joe Tidy |website=BBC News |url=https://www.bbc.com/news/articles/cpe3zgznwjno |date=20 July 2024 |title=CrowdStrike IT outage affected 8.5 million Windows devices, Microsoft says}}</ref><ref name=theBreakingChange>{{cite web |author=Piet Kerkhofs |url=https://www.eye.security/blog/crowdstrike-falcon-blue-screen-issue-updates |date=19 July 2024 |title=CrowdStrike Falcon and Microsoft blue screen issue updates |website=Eye Security |access-date=19 July 2024}}</ref><ref name=23JulReview>{{cite web |author=Tim Warren |website=The Verge |url=https://www.theverge.com/2024/7/23/24204196/crowdstrike-windows-bsod-faulty-update-microsoft-responses |date=23 July 2024 |title=Inside the 78 minutes that took down millions of Windows machines}}</ref>

====Recovery policy====
Recovery might be specified via [[Security Assertion Markup Language]] (SAML), which can also implement [[Single sign-on]] (SSO) for some applications; in the [[zero trust security model]] identification, authorization, and authentication are separable concerns in an SSO session. When recovery of a site is indicated (viz. a blue screen of death is displayed on an airport terminal screen){{efn|name=crowdstrikeBootloop}} personal site visits might be required to remediate the situation.<ref name=2004DefectDetection />

==== Examples ====
* [[Windows NT 4.0]]<ref>{{cite book | last=Ruley | first=John D. | author2= David Methvin | author3=Tom Henderson | author4=Martin Heller | date=1997 | url=https://books.google.com/books?id=fA0gDTOdUWUC&q=%22infinite+loop%22+%22reboot%22 | title=Networking Windows NT 4.0: Workstation and Server | publisher=Wiley | page=257 | isbn=9780471175025 | via=Google Books}}</ref>
* [[Windows 2000]]<ref>{{cite journal | last=Shultz | first=Gregory | date=February 2001 | url=https://www.proquest.com/docview/191083238 | title=Disabling automatic reboot prevents possible reboot loop | journal=Windows Professional | publisher=Element K Journals | volume=6 | issue=2 | page=9 | id={{ProQuest|191083238}} | via=ProQuest}}</ref>
* [[Windows Server]]<ref>{{Cite web |title=New Windows Server updates cause DC boot loops, break Hyper-V |url=https://www.bleepingcomputer.com/news/microsoft/new-windows-server-updates-cause-dc-boot-loops-break-hyper-v/ |access-date=2022-05-17 |website=[[BleepingComputer]] |language=en-us}}</ref>
* [[Windows 10]]<ref>{{Cite web |author1=Paul Wagenseil |date=2021-01-21 |title=Windows 10 update sending PCs into endless boot cycle: What to do |url=https://www.tomsguide.com/news/windows-10-automatic-repair-boot-loop |access-date=2022-05-20 |website=[[Tom's Guide]] |language=en}}</ref>
* The [[Nexus 5X]]<ref>{{Cite web |last=Hollister |first=Sean |date=2021-10-19 |title=Google has tried everything but building the best phone |url=https://www.theverge.com/2021/10/19/22734039/google-pixel-6-pro-price-marketing-premium-flagship-editorial |access-date=2022-05-17 |website=[[The Verge]] |language=en}}</ref>
* [[Android 10]]: when setting a specific image as wallpaper, the [[luminance]] value exceeded the maximum of 255 which happened due to a [[rounding error]] during conversion from [[sRGB]] to [[RGB color spaces|RGB]]. This then crashed the SystemUI component on every boot.<ref>{{Cite web |title='It was unintentional,' says creator of 'cursed' Android wallpaper |url=https://www.theweek.in/news/sci-tech/2020/06/11/it-was-unintentional-says-creator-of-cursed-android-wallpaper.html |access-date=2022-05-19 |website=The Week |language=en}}</ref><ref>{{Cite web |last=Hager |first=Ryne |date=2020-06-01 |title=Google thinks it has solved the mystery of the cursed bootlooping wallpaper |url=https://www.androidpolice.com/2020/06/04/choosing-the-wrong-wallpaper-can-bootloop-your-android-phone/ |access-date=2022-05-19 |website=Android Police |language=en-US}}</ref>
* [[Google Nest]] hub<ref>{{Cite web |last=Peckham |first=James |date=2022-03-29 |title=Google Nest Hub gets a new UI that's so fresh it could bootloop your smart display |url=https://www.androidpolice.com/google-nest-hub-ui-redesign-may-bootloop-smart-display/ |access-date=2022-05-19 |website=Android Police |language=en-US}}</ref>
* [[LG smartphone bootloop issues]]
* On 19 July 2024, an update of [[CrowdStrike]]{{'}}s Falcon software caused the [[2024 CrowdStrike incident]] resulting in [[Microsoft Windows]] systems worldwide stuck in bootloops or [[recovery mode]].{{efn|name=crowdstrikeBootloop|1= CrowdStrike reverted the content update at 05:27 UTC,<ref name="crowdstrike.com-240719">{{Cite web |title=Statement on Falcon Content Update for Windows Hosts |url=https://www.crowdstrike.com/blog/statement-on-windows-sensor-update/ |access-date=19 July 2024 |website=crowdstrike.com |language=en}}</ref> This left machines stuck in a [[boot loop]] or in [[recovery mode]].<ref>{{Cite web |last=Baran |first=Guru |date=19 July 2024 |title=CrowdStrike Update Pushing Windows Machines Into a BSOD Loop |url=https://cybersecuritynews.com/crowdstrike-update-bsod-loop/ |access-date=19 July 2024 |website=Cyber Security News |language=en-US}}</ref> and devices booted after the revert were not affected.<ref name=theBreakingChange /><ref>{{Cite web |date=19 July 2024 |title=Botched security update breaks Windows worldwide, causing BSOD and crashes |url=https://www.neowin.net/news/botched-security-update-breakes-windows-worldwide-causing-bsod-and-crashes/ |access-date=19 July 2024 |website=Neowin |language=en}}</ref>}}