Relationship between CentOS and Rhel

What CentOS is.

CentOS is a freely available source code enterprise-class Linux distribution based on Red Hat enterprise-class Linux. Each version of the CentOS will receive seven years of support (via a security update). The new version of the CentOS is released every two years, and each version of the CentOS is updated periodically (about every six months) to support new hardware. In this way, establish a secure, low maintenance, stable, high predictive, high repeatability of the Linux environment.

CentOS (Community Enterprise operating System) is one of the Linux distributions that is compiled from the source code released by Red Hat Enterprise Linux in accordance with open source rules. Because of the same source code, some servers that require a high degree of stability are used by CentOS instead of the commercial version of Red Hat Enterprise Linux. The difference between the two is that CentOS does not contain closed source code software.

CentOS is a community of Open-source software contributors and users. It compiles the Rhel source code and becomes one of many communities that publish new releases, and in the process of continuous development, the CentOS community is constantly merging with other communities of its kind, making CentOS Linux the most widely used Rhel compatible version. CentOS Linux is no less stable than rhel, the only thing that is lacking is technical support because it is a free version released by the community.

CentOS Linux and Rhel products have a strict version of the relationship, such as the use of RHEL4 source code recompile release is CentOS Linux 4.0,rhel5 corresponding CentOS linux 5.0,rhel6 Linux 6. Because the Rhel product has a long life cycle (typically 3-5 years of official support), Red Hat has repackaged the cumulative update into an updated release, often referred to as Rhel update, at intervals after the release of the Rhel series.

For example, the 1th updated version of RHEL5 is called Rhel 5 Update 1, and the user is often called Rhel 5.1. Each Rhel update CentOS community released by Red Hat publishes a corresponding update release, for example, according to Rhel 5 Update 1, CentOS will recompile and package the CentOS Linux 5.1 release. CentOS Linux and the corresponding version number of the Rhel release has package-level binary compatibility, that is, if an RPM package can be installed to run in the Rhel product, it can be installed normally in the corresponding version of CentOS Linux. CentOS Linux has been used more and more widely because of its compatibility with Rhel and the stability of enterprise-class application, and allow users to use it freely.

CentOS features can be interpreted as the Red Hat as series CentOS. It is a complete release of the red Hat as improvements. There is no difference between the various operations, use, and red Hat. CentOS is completely free and there is no problem with red HAT AS4 requiring serial numbers. CentOS's unique yum command supports online upgrades that allow you to update your system instantly, unlike Red Hat, which requires money to buy support services. CentOS fixes a number of red HAT as bugs. CentOS Version Description: CentOS3.1 equivalent to Red Hat AS3 Update1 CentOS3.4 equivalent to Red Hat AS3 Update4 is equivalent to Red Hat CentOS4.0.

1.2 Installation version

　　This installation we choose CetOS6.0 version, the following from a few aspects of this version. Integrates kernel based virtualization. CentOS 6 is a kernel based virtualization that integrates the KVM management program into the kernel. Such features help CentOS 6.0 of users migrate virtual machines easily between hosts, deploy and manage IT resources more flexibly, and effectively conserve resources for the enterprise. Leveraging the hardware abstraction of the kernel enables applications to be independent of the underlying hardware and to increase CPU and memory scalability so that each server can accommodate more virtual machines. Enhance system and resource management capabilities. The standards-based Linux Manageability Specification (SBLIM) uses web-based Enterprise Management (WBEM) to manage systems. Replacing MKINITRD with dracut minimizes the impact of underlying hardware changes, is easier to maintain, and makes it easier to support third-party drivers. Enhanced power management, on-time kernel improvements enable CentOS 6.0 to place processors without active tasks in idle state to reduce CPU temperature and further reduce energy consumption. With the help of a new framework called control group (i.e. cgroups), CentOS 6.0 provides fine-grained control, allocation, and management of hardware resources. Cgroups runs at the process group level and can be used to manage resources from CPU, memory, network, and hard disk I/O for the application. Enhance the reliability, usability and applicability of the system. CentOS 6.0 provides hot-swappable features with new hardware capabilities and can be checked through enhanced error checking of AER PCIe devices. CentOS 6.0 includes advanced data integrity features (DIF/DIX). This type of feature checks and verifies data from the application through hardware. The introduction of the Automated Defect Reporting Tool (ABRT) provides the identification and reporting of system anomalies, including kernel failures and user-space application crashes. Improved scalability and kernel performance. CentOS 6.0 provides the flexibility to adapt to future systems with scalable capabilities ranging from optimized support for a large number of CPUs and memory configurations to the ability to handle a larger number of system interconnect buses and peripherals. When virtualization becomes as ubiquitous as bare-metal deployments, these capabilities are appropriate for bare-metal environments and virtualized environments. CentOS 6.0 improves kernel performance by allocating computing time more equitably between processors by allowing higher-priority processes to handle disturbances at a minimal lower priority. At the same time, CentOS 6.0 improves multiple multiprocessor lock synchronizations to eliminate unnecessary locking events, replace many rotational (spin) locks with sleep locks, and adopt more efficient locking primitives. Stable application development and production platform. CentOS 6.0 is a high-performance, highly scalable, distributed, memory-based object caching system that greatly improves the speed of dynamic Web applications. In Web The basic architecture has mainly improved the three aspects of Apache, squid and memcached. With Java performance support, tight integration of CentOS 6.0 and OPENJDK includes support for Java probes in Systemtap to support better Java debugging. At the same time, CentOS 6.0 is also gradually improving the support of Tomcat 6.

Official website and Documentation

Official homepage: http://www.centos.org/

Official wiki:http://wiki.centos.org/

Official Chinese Document: Http://wiki.centos.org/zh/Documentation

Installation Instructions: http://www.centos.org/docs/