mainline 、longterm、stable、linux-next、snapshot这些名词，都是linux kernel source的标记名称，可以理解为代号。
mainline
mainline指由Linus Torvalds亲自制作的内核发布版，是官方当前最新版本的kernel source。在Torvalds对所有其他程序员所做出的重大变化进行整合，并且对先前版本的bug进行几轮修复之后，大约每十周正式发布一个新版本。mainline事实上代表着一个linux kernel分支，这个分支有另一个名称，叫做vanilla。
longterm
longterm，是Long Term Support的缩写，长期维护的意思。
stable
stable顾名思义 稳定版
linux-next、snapshot
linux-next和snapshot，都是代码提交周期结束之前生成的快照 用于给Linux代码贡献者们做测试。
Development model开发模式
The current development model of the Linux kernel is such that Linus Torvalds makes the releases of new versions, also called the “vanilla” or “mainline” kernels, meaning that they contain the main, generic branch of development. This branch is officially released as a new version approximately every ten weeks, after Torvalds does an initial round of integrating major changes made by all other programmers, and several rounds of bug-fix pre-releases.
Linux内核目前的发展模式是这样的： Linus Torvalds制作新版本内核（也称为“”vanilla” 或者”mainline” 内核）的发布，这意味着它们含有development（开发）的主要的、通用的分支。这个分支，在Torvalds对所有其他程序员所做出的重大变化进行整合，并且对先前版本的bug进行几轮修复之后，大约每十周正式发布一个新版本。
Relation with Linux distributions
Most Linux users run a kernel supplied by their Linux distribution. Some distributions ship the “vanilla” or “stable” kernels. However, several Linux distribution vendors (such as Red Hat and Debian) maintain another set of Linux kernel branches which are integrated into their products. These are by and large updated at a slower pace compared to the “vanilla” branch, and they usually include all fixes from the relevant “stable” branch, but at the same time they can also add support for drivers or features which had not been released in the “vanilla” version the distribution vendor started basing their branch from.
大多数Linux用户运行的是由某个Linux发行版提供的内核。一些发行版采用”vanilla” 或者 “stable” 内核。然而，一些Linux发行商（如Red Hat和Debian Linux）坚持使用另一组内核分支集成到他们的产品中。与”vanilla”分支相比，总的来说这些内核的更新速度较慢，并且他们通常包含了来自于相关“stable”分支的所有修复，不过他们同时还可以添加驱动程序支持或某些”vanilla”内核中没有发布的功能。
