Linux kernel is the core of computer operating system. A complete Linux distribution includes a series of software, such as kernel and some other file-related operations, user management system and package manager. Each tool is a small part of the whole system. These tools are usually independent projects, developed and maintained by the corresponding developers.

The aforementioned Linux kernel, including the current version and version history (earlier version), can be found in www.kernel.org. Many distributions of Linux may be based on different kernel versions. For example, the popular RHEL6 distribution is based on the old but stable version 2.6.32 Linux kernel. Other distributions may be updated quickly to adapt to the latest kernel version. It should be noted that the kernel is not an either-or proposition. For example, RHEL6 introduces many improvements of the new version of the kernel in the kernel of 2.6.32.

Other basic tools and components provided by each distribution also include the following contents: C/C++ compiler, gdbdebugger debugging tool, core system library application, bottom interface for drawing, advanced desktop environment, and numerous installation and update systems including kernel.

Many different Linux distributions meet the different needs of different users and organizations. Large commercial organizations usually prefer to use the distributions provided by Red Hat, SUSE and Canonical (Ubuntu).

Fedora is a community version based on RHEL, CentOS, Scientific Linux and Oracle Linux. Compared with RHEL, Fedora packages more software packages. One of the reasons is that diverse communities participate in the construction of Fedora; It's not just a company. In this process, CentOS is used for activities, demonstrations and experiments, because it is free for end users and has a longer release cycle than Fedora (usually a new version is released every six months or so).

The relationship between SuSE, SuSE Linux Enterprise Server (SLES) and openSUSE is similar to that of Fedora, Red Hat Enterprise Linux and CentOS.

Debian is the upstream of many distributions, including Ubuntu, and the upstream of distributions such as Linux Mint. Debian is widely used in the fields of servers and desktop computers. Debian is a pure open source project, focusing on a key point, stability. It also provides users with the largest and most complete software warehouse.

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