When RedHat is released, there are two ways: binary and source code distribution. Regardless of the distribution method, you can get it for free (for example, download it from the Internet) and release it again. But if you use their online upgrades (including patches) or consulting services, you must pay.
CentOS and Redhat relationship
RedHat has always provided a source code distribution method. CentOS recompiles the source code issued by RedHat to form a usable binary version. Since the source code of LINUX is GNU, it is legal from obtaining the source code of RedHat to compiling it into a new binary. Only RedHat is a trademark, so the RedHat trademark must be removed in the new release.
RedHat's attitude towards this kind of distribution is: "We are actually not opposed to this kind of distribution. Users who really pay us, they value not the system itself, but the commercial services we provide." So, CentOS can Get all the features of RedHat, even better software. But CentOS does not provide commercial support to users, and certainly does not bear any commercial responsibility.
If you want to transfer your RedHat to CentOS, because you don't want to pay for the RedHat upgrade. Of course, you must have rich experience in using UNIX, so RedHat's commercial technical support is not important to you. But if you are a purely business enterprise, it is still recommended that you purchase RedHat software and purchase corresponding services. This can save your IT management costs and get professional services.
In a word, whether to choose CentOS or RedHat depends on whether your company has the corresponding technical strength:
1、 You can completely understand CentOS as the RedHat AS series! It is completely released after the improvement of RedHat AS, and various operations and uses are no different from RedHat.
2、 CentOS is completely free, there is no need for serial numbers like RedHat AS series
3、 CentOS's unique yum command supports online upgrades, which can update the system instantly, unlike RedHat that requires money to purchase support services
4、 CentOS fixes many RedHat AS bugs
5、 CentOS version description:
CentOS4.0 is equivalent to RedHat AS4
CentOS4.1 is equivalent to RedHat AS4 U1
CentOS4.2 is equivalent to RedHat AS4 U2
CentOS4.3 is equivalent to RedHat AS4 U3
CentOS4.4 is equivalent to RedHat AS4 U4
**Red Hat **
Redhat has two major Linux product series: free and paid
1 ) Free Fedora Core series
It is mainly used in the desktop version and provides support for more new features.
Red Hat’s products include Red Hat Linux (such as Redhat 8, 9) and Red Hat Enterprise Linux for enterprise releases, both of which can be obtained and used for free via network FTP, but in 2003, Red Hat Linux was discontinued Development, which is why there is no Redhat10. Its project is replaced by the Fedora Project, and it is released under the name Fedora Core and is available to ordinary users for free. The Linux distribution of Fedora Core has been updated very quickly. A new version will come out in about half a year. The current version is Fedora Core 6. This Fedora Core experiment has a strong flavor, and new features are added to it every time it is released. The successful results obtained will be adopted in the release of RHEL. In spite of this, unstable products that are frequently improved and updated are not the best choice for enterprises. Most enterprises still choose paid RHEL products.
2 ) Charged Enterprise series
This series is divided into: AS/ES/WS and other branches. Red Hat Enterprise Linux: The enterprise version of redhat, abbreviated as RHEL. Including the following versions:
1、 Red Hat Enterprise Linux AS
Red Hat Enterprise Linux AS (Advanced Server) is the most high-end product in enterprise Linux solutions. It is designed for key enterprise applications and data centers. Red Hat Enterprise Linux AS is the only product that supports IBM i series, p series and z series/S-390 systems. On the Intel X86 platform, Red Hat Enterprise Linux AS can support more than 2 CPUs and more than 8GB of memory.
The typical application environment of Red Hat Enterprise Linux AS is as follows:
Database and database application software; WEB and middleware; CRM, ERP, SCM
2、 Red Hat Enterprise Linux ES Red Hat Enterprise Linux ES (Entry Server)
Provides a server operating system from enterprise portal to enterprise middle-level application for the Intel X86 market. It supports systems with 1-2 CPU and less than 8GB memory. It provides the same performance as Red Hat Enterprise Linux AS, except that it supports smaller systems and lower costs.
The typical application environment of Red Hat Enterprise Linux ES is as follows:
Company WEB architecture; network edge applications (DHCP, DNS, firewall, etc.); mail and file/printing services; small and medium-sized databases and departmental application software
3、 Red Hat Enterprise Linux WS
Red Hat Enterprise Linux WS (Workstation) is the desktop/client partner of Red Hat Enterprise Linux AS and ES. Red Hat Enterprise Linux WS supports intel and AMD systems with 1-2 CPU, which is the best environment for desktop applications. It contains a variety of commonly used desktop application software (Office tools, mail, instant messaging, browsers, etc.), can run various client-server configuration tools, software development tools and various application software (such as EDA and Oil/Gas application software) ). Red Hat Enterprise Linux Ws and server products are compiled from the same source code, but it does not provide network service functions (such as DNS and DHCP), and it is only suitable for client applications.
AS, ES, WS relationship
Advanced Server, abbreviated as AS. On the basis of the standard Linux kernel, AS has made performance enhancements, and improved reliability, and integrates many common server drivers. It can easily identify the disk array cards and other equipment of common rack servers such as IBM/DELL/HP. The main AS version 2.x/3.x/4.x, which is what we call AS3/AS4, each version has several upgrades, for example, after the first AS4 launched, it encountered some updates. AS4 Update1 will be released at this time, and there will be AS4 Update2/Update3 and so on in the future, which will be referred to as AS4u1/AS4u2/AS4u3. This is very similar to Microsoft's release form, Microsoft's Windows NT4 from SP1 to SP6, Windows 2000 from SP1 to SP4 and so on. The main program package versions contained in these Update versions of AS have certain differences. It is best not to mix them, otherwise problems are prone to occur. The installation packages of Prima and Plesk are designed specifically for various distributions. They are usually marked on the download page, which versions and which update systems are supported.
ES is a simplified version of AS. The difference between it and the common AS series is that AS supports more than 4 CPUs, while ES can only support two CPUs. There is no difference between AS and ES in most packages, only a few packages such as the kernel. The price difference between AS and ES is relatively large, and ES is usually used in the OEM version purchased with the server. For example, if you buy a DELL server, the Linux will be the ES series. If you want to match the AS series, you need to spend thousands of dollars.
WS, a further simplified version of ES, is mainly aimed at the desktop office market within the enterprise and is rarely used in China.
Redhat's Fedora Core Linux and Enterprise Linux both need to follow the GNU protocol, that is, they need to release their own source code. Therefore, for free Fedora Core Linux, you can download the ISO CD directly from the Redhat website, and you can also download the ISO of SRPM, which is the source CD of the program package. For the charged Enterprise Linux series, it is a commercial product, so ISO files cannot be downloaded from the website, and a formal authorization is required. Since Enterprise Linux also needs to follow the GNU agreement, the source code must be released. So on the Redhat website, you can get the SRPM source ISO file of the AS/ES/WS series. These files can be downloaded freely, code modified, recompiled and used.
CentOS
The Community ENTerprise Operating System project was born, and its acronym is CentOS. The CentOS community downloads all the source codes on the Redhat website and recompiles them. After recompilation, because AS/ES/WS are commercial products, all Redhat logos and logos must be changed to their own CentOS logos. For example, after compiling the original SRPM source code of AS4, it becomes CentOS 4.0. After the source code of AS4Update1 is compiled, it becomes CentOS4.1. After the source code of AS4Update2 is compiled, it becomes CentOS4.2. In the same way, CentOS 3.x/4.x corresponds to the corresponding version.
Therefore, CentOS is the free version of Redhat's AS/ES/WS. Using CentOS, you can get the same performance and experience as AS/ES. In addition to providing standard ISOs numbered 1~4 or 1~5, CentOS also provides a Mini Server CD with 1CD. The system installed with the Server CD is a minimal Linux kernel plus commonly used packages such as httpd/mysql, and does not include Xwindows desktop and other useless software for the server.
The difference between CentOS and REDHAT:
The GPL is the software license used by the Linux kernel. The feature of the GPL is: if you use other people's code to modify it, you must publish the modified code.
All Linux is licensed under the GPL. The GPL license allows GPL software to be sold for money, but the source code must be published, so the code of each Linux distribution is fully public, but the person who uses the code must also publicly modify it. Code.
Redhat's code is public, but his binary RPM package update is not free, which does not violate the GPL license. So some people began to think of establishing the CentOS project.
Since the source code of Redhat is public, the people of the CentOS project take it and compile it by themselves. The same code and the same compiler will naturally compile the same thing. It’s just that Redhat’s Logo and corresponding information are deleted, and the core management tool is still rpm. It’s just a free software package manager yum (yellow dog update manager) instead of up2date in Redhat. Up2date update is connected to Redhat. For fee-paying service sites, the service code purchased with money is certified.
There are many users of CentOS, because many people around the world want to use Redhat but are troubled by Redhat's charging services. Now CentOS is among the top 10 Linux distributions, and the tenth distribution of this page is CentOS: Top Ten Distributions
In terms of quality, CentOS should theoretically be the same as Redhat, after all, it is the same source code.
The above 6 points are enough to explain CentOS.
**What is FreeBSD: **
FreeBSD is a complete system. All small commands such as ls and cd are developed by their own project team. The Linux distribution is actually to download a Linux kernel, download GNU Coreutils (including commonly used core small commands), and customize it yourself system. You should remember that I compiled a system manually a few days ago. FreeBSD is a Unix-Like operating system evolved from 4.4BSD and does not also use the Linux kernel.
The software license used by FreeBSD is BSDL. The characteristics of BSDL are: you can use my code for free, and you don’t need to disclose the modified code based on my code. If there is a problem with my code, please don’t sue me (original: don' t pay me, don't sue me). Many people who like BSDL mainly because they believe that as long as the code can be used to the greatest extent, it is the best, unlike GPL, the code has to be paid back. So many network equipment and some commercial companies sponsor the development of FreeBSD, which is a completely free software project: freebsdfoundation.org
Reference recommendation:
The difference and connection between Centos and Redhat
[ Linux distribution: CentOS, Ubuntu, RedHat, Android, Tizen, MeeGo](https://blog.csdn.net/Linux%E5%8F%91%E8%A1%8C%E7%89%88%EF%BC %9ACentOS%E3%80%81Ubuntu%E3%80%81RedHat%E3%80%81Android%E3%80%81Tizen%E3%80%81MeeGo)
Recommended Posts