Linux Versions
Up to kernel version 2.5, Linux identified kernels through a simple numbering scheme. Each version was characterized by three numbers, separated by periods. The first two numbers were used to identify the version; the third number identified the release. The first version number, namely 2, has stayed unchanged since 1996. The second version number identified the type of kernel: if it was even, it denoted a stable version; otherwise, it denoted a development version.
As the name suggests, stable versions were thoroughly checked by Linux distributors and kernel hackers. A new stable version was released only to address bugs and to add new device drivers. Development versions, on the other hand, differed quite significantly from one another; kernel developers were free to experiment with different solutions that occasionally lead to drastic kernel changes. Users who relied on development versions for running applications could experience unpleasant surprises when upgrading their kernel to a newer release.
During development of Linux kernel version 2.6, however, a significant change in the version numbering scheme has taken place. Basically, the second number no longer
identifies stable or development versions; thus, nowadays kernel developers introduce large and significant changes in the current kernel version 2.6. A new kernel 2.7
branch will be created only when kernel developers will have to test a really disruptive change; this 2.7 branch will lead to a new current kernel version, or it will be backported to the 2.6 version, or finally it will simply be dropped as a dead end.
Linux 的版本
在Linux内核2.5版本之前，Linux通过一个简单的编号方案来识别不同的内核。每个版本都用3个数字加’.'分隔符来描述。前两个数字用来识别版本，第三个数字用来标识发行号。第一个版本号是2，在1996年之前未发生改变，第二个版本号用来标识内核的类型：如果是偶数则表示该版本是稳定版，如果是奇数则表示该版本是开发版本。
顾名思义，稳定版经过了Linux发布者和内核红客们的彻底的检查并保证稳定运行。一个新的稳定版只会在解决了bug或者增加了新的设备驱动之后才会发布。而不同开发版本之间则有非常大的不同。内核开发者可以自由的尝试多种不同方案，而这种尝试偶尔会导致内核产生剧烈的改动。这样一来，那些依赖开发版本的用户在将他们懂得内核更新到更新的版本时就会经历不愉快的体验。
在开发Linux内核2.6版本时，版本方案发生了重大的变化。总的来说，变化主要是第二个数字不再表示稳定版或开发版；因此，现在有很多内核开发者在当前的Linux2.6内核中引入了一些重要且比较大的变化。只有在内核开发者不断的不对内核做一个颠覆性的变革时一个新的2.7分支才会创建出来，这个2.7分支将最终导致发布一个新的内核版本，或者直接移植到2.6版本中，亦或者最终走入一个死胡同而被丢弃。