Update schedule
See also: Android version history
Google provides major incremental upgrades to Android every six to nine months, with confectionery-themed names, which most devices are capable of receiving over the air.[104]The latest major release is Android 6.0 "Marshmallow".
Compared to its primary rival mobile operating system, iOS, Android updates typically reach various devices with significant delays. Except for devices with the Google Nexusbrand, updates often arrive months after the release of the new version, or not at all.[105] This is partly due to the extensive variation in hardware of Android devices, to which each upgrade must be specifically tailored, as the official Google source code only runs on their own Nexus devices. Porting Android to specific hardware is a time- and resource-consuming process for device manufacturers, who prioritize their newest devices and often leave older ones behind.[105] Hence, older smartphones are frequently not updated if the manufacturer decides it is not worth the investment of resources, although the device may be compatible. This problem is compounded when manufacturers customize Android with their own interface and apps, which must be reapplied to each new release. Additional delays can be introduced by wireless carriers who, after receiving updates from manufacturers, further customize and brand Android to their needs and conduct extensive testing on their networks before sending the upgrade out to users.[105]
The lack of after-sale support from manufacturers and carriers has been widely criticized by consumer groups and the technology media.[106][107] Some commentators have noted that the industry has a financial incentive not to upgrade their devices, as the lack of updates for existing devices fuels the purchase of newer ones,[108] an attitude described as "insulting".[107] The Guardian complained that the method of distribution for updates is complicated only because manufacturers and carriers have designed it that way.[107] In 2011 Google partnered with a number of industry players to announce an "Android Update Alliance", pledging to deliver timely updates for every device for 18 months after its release;[109] however, there has not been another official word about that alliance since its announcement.[105][110]
In 2012 Google began decoupling certain aspects of the operating system (particularly core applications) so they could be updated through Google Play Store independently of the operating system. One of these components, Google Play Services, is a closed-source system-level process providing APIs for Google services, installed automatically on nearly all devices running Android version 2.2 and higher. With these changes, Google can add new operating system functionality through Play Services and application updates without having to distribute an upgrade to the operating system itself. As a result, Android 4.2 and 4.3 contained relatively fewer user-facing changes, focusing more on minor changes and platform improvements.[3][111]
Linux kernel
Android's kernel is based on one of the Linux kernel's long-term support (LTS) branches. Since April 2014, Android devices mainly use versions 3.4 or 3.10 of the Linux kernel.[112][113] The specific kernel version depends on the actual Android device and its hardware platform;[114][115][116] Android has used various kernel versions since the version 2.6.25 that was used in Android 1.0.[41]
Android's variant of the Linux kernel has further architectural changes that are implemented by Google outside the typical Linux kernel development cycle, such as the inclusion of components like Binder, ashmem, pmem, logger, wakelocks, and different out-of-memory (OOM) handling.[117][118][119] Certain features that Google contributed back to the Linux kernel, notably a power management feature called "wakelocks", were rejected by mainline kernel developers partly because they felt that Google did not show any intent to maintain its own code.[120][121][122] Google announced in April 2010 that they would hire two employees to work with the Linux kernel community,[123] but Greg Kroah-Hartman, the current Linux kernel maintainer for the stable branch, said in December 2010 that he was concerned that Google was no longer trying to get their code changes included in mainstream Linux.[121] Some Google Android developers hinted that "the Android team was getting fed up with the process," because they were a small team and had more urgent work to do on Android.[124]
In August 2011, Linus Torvalds said that "eventually Android and Linux would come back to a common kernel, but it will probably not be for four to five years".[125] In December 2011, Greg Kroah-Hartman announced the start of Android Mainlining Project, which aims to put some Android drivers, patches and features back into the Linux kernel, starting in Linux 3.3.[126] Linux included the autosleep and wakelocks capabilities in the 3.5 kernel, after many previous attempts at merger. The interfaces are the same but the upstream Linux implementation allows for two different suspend modes: to memory (the traditional suspend that Android uses), and to disk (hibernate, as it is known on the desktop).[127]Google maintains a public code repository that contains their experimental work to re-base Android off the latest stable Linux versions.[128][129]
The flash storage on Android devices is split into several partitions, such as
/system for the operating system itself, and /data for user data and application installations.[130]In contrast to desktop Linux distributions, Android device owners are not given root access to the operating system and sensitive partitions such as /system are read-only. However, root access can be obtained by exploiting security flaws in Android, which is used frequently by the open-source community to enhance the capabilities of their devices,[131] but also by malicious parties to install viruses and malware.[132]
Android is a Linux distribution according to the Linux Foundation,[133] Google's open-source chief Chris DiBona,[134] and several journalists.[135][136] Others, such as Google engineer Patrick Brady, say that Android is not Linux in the traditional Unix-like Linux distribution sense; Android does not include the GNU C Library (it uses Bionic as an alternative C library) and some of other components typically found in Linux distributions.[137]
EmoticonEmoticon