What is CentOS in 2021?

Short explanation.

CentOS explained.

CentOS (Community ENTerprise Operating System) is an operating system based on the Linux kernel for PCs, servers and VPS. The distribution is one of the most widely used non-commercial Linux versions worldwide and is based on the RedHat Enterprise Linux (RHEL) system. Like the RedHat version, CentOS is tailored to company needs and binary compatible with RHEL. In contrast to RHEL, CentOS can be used by anyone free of charge. The latest version is Centos 8 released in May 2021. This operating system is intended for use by companies and enterprises.

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Long explanation.

What is CentOS?

Enterprise operating systems on VPS must meet a number of important criteria: For example, it is of crucial importance that the appropriate system management software is linked to a comprehensive range of support from the development team or the provider. This is the only way to ensure regular improvements to the software and bug fixes as well as security updates to protect against new malware and to close discovered security gaps. It is just as important for the constant operation of corporate applications that the stability of the interfaces between the operating system and the programs used is guaranteed (backward compatibility). An enterprise solution that is particularly popular in the web sector and also open source is the CentOS Linux distribution.

Table of Contents

  • The Story of the RHEL Descendant
  • This is what defines the CentOS distribution
  • What are the system requirements for distribution?
  • The Linux operating system offers these features
  • Special Interest Groups: The working groups of the CentOS community
  • This is how the installation works
  • CentOS Linux on your VPS – a conclusion

CentOS: The Story of the RHEL Descendant

Community Enterprise Operating System, or CentOS for short, is a Linux distribution that was released in March 2004. The open source project, which is developed and supported by a huge community, is based on the source packages of Red Hat Enterprise Linux (RHEL) – a commercial distribution that can only be used in combination with paid support contracts. Red Hat, the provider of RHEL, is for its part obliged to make the source code publicly available in order to comply with the various free licenses of the integrated software components. As part of the CentOS project, the developers were therefore able to easily build on the source code from RHEL when programming an equivalent that could be used free of charge.

All CentOS versions published so far are based on the corresponding release versions of RHEL and are also binary compatible with the Red Hat product. All applications that exist for the commercial enterprise system also work without additional compilers and without any restrictions. At the beginning of 2014, employees from Red Hat and developers of the still independent CentOS project joined forces in the so-called “Governing Board”. Since then, this team has primarily been responsible for the further development of distribution and the supervision of the various working groups (system core, support, design, etc.).

This is what defines the CentOS distribution

Like its role model RHEL, CentOS is an enterprise platform that is primarily suitable for use in companies and large organizations. In principle, the Linux distribution can also be used in the private sector, although the developers do not focus on this. In addition, the Linux distribution is very popular as an operating system for VPS web servers – according to w3techs.com (as of January 2017), only Ubuntu and Debian are used more frequently.

As an enterprise distribution, CentOS distinguishes those features that make RHEL so valuable for companies:

  • VPS Stability: CentOS is constantly being further developed in order to be able to offer the perfect platform for the latest software. However, the aspect of compatibility with older applications is always taken into account. Future-oriented development steps are always carried out in such a way that the stability of active components is guaranteed. Furthermore, the system impresses with its strong performance in the areas of virtualization (on a kernel-based virtual machine basis) and high availability, which is why distribution also cuts a fine figure when operating virtualization and cloud servers.
  • VPS Security: The topic of security is more important today than ever, which is why CentOS is an excellent choice as an enterprise solution with a RHEL background. The underlying source code from Red Hat is already at a high level in terms of security thanks to the proactive detection of vulnerabilities by the American software company’s security team. In addition, with every CentOS update and with the integration of new programs, security and error checks come first. The Linux distribution also supports the kernel extension SELinux (Security-Enhanced Linux) – an open source product that is the result of a collaboration between Red Hat and the NSA. This program implements authorization controls for the use of computer resources and thus protects against unauthorized access.
  • VPS long maintenance and support cycles: Since the first CentOS version, both large and small releases have been closely linked to the corresponding publications by RHEL. The development team provides a period of 2 to 6 weeks (or a few hours for small updates) for the process of code adaptation that has now been implemented. The version numbers are simply retained (e.g. RHEL 6.2 à CentOS 6.2). Since version 7, a time stamp indicating the release of the basic code has also been appended. For example, version 7.0-1406 indicates the source was released in June 2014. In addition to versioning, CentOS has also adopted the guidelines for the maintenance period: up to 7 years are now provided for general support and up to 10 years for the provision of security updates (up to version 5.0 it was up to 4 and 7 years).
  • As with RHEL, it is installed using the beginner-friendly, graphic manager Anaconda. CentOS also uses proven Red Hat components for package management (RPM) and software management (yum). But even if RHEL programs usually run under the free counterpart, they often lack the certifications and support from the respective manufacturer, which is why it is not always guaranteed that they will function properly under CentOS.

VPS CentOS: What are the system requirements for distribution?

Depending on the respective CentOS version, there are logically very different requirements for the hardware. CentOS 5, for example, still manages with 512 MB RAM if you want to operate it via a graphical user interface, and an economical 128 MB if operation via the command line is sufficient for you. In addition, 5 GB of storage space is recommended (at least 1 GB). Version 6 requires 392 MB for the command line variant, which is no longer available as a separate option in CentOS 7, and requires 1 GB of RAM on non-x86 architectures. The aforementioned 7th version of the Linux distribution requires 1 GB of RAM and 20 GB of hard disk space (at least 10 GB) by default.

The various releases of the RHEL descendant also differ in terms of the hardware architectures supported. Many of the portings for version 7 were carried out by the working group “Alternative Architecture Special Interest Group” (AltArch SIG) and added later.

The Linux operating system offers these features

The current CentOS version 8.4 (as of June 2021) is based on the Linux kernel 3.10.0 including the security extension SELinux that has already been used and has implemented GCC (GNU Compiler Collection). This collection contains compilers for the most important programming languages: such as C, C ++ and Java. The Linux distribution also supports hyperthreading (division of a processor into two virtual processors to increase performance), plug and play, Bluetooth and version 6 of the Internet protocol (IPv6). Compatibility libraries exist for the older versions CentOS 5, 6 and 7. The standard distribution package also includes the following software components:

  • Web server: httpd 2.4.6 (Apache)
  • LAN manager: Samba-4.9
  • Database: MariaDB 10.6, PostgreSQL 14.0
  • Scripting languages: PHP 7.4, Python 3, Perl 5.24
  • Desktop interface: Gnome 3.38, KDE 5.0
  • Display server: X.org 1.20.11
  • Email client: Evolution 3.12, Thunderbird 78.12
  • Internet browser: Firefox 90
  • Office suite: LibreOffice 7.1

Special Interest Groups: The working groups of the CentOS community

With the founding of the governing board, the further development of the Linux system was structured. Since then, different teams – consisting of members of the broad community – have been working in different working groups, which either have the purpose of expanding the CentOs distribution or optimizing the functional aspects of the CentOS project (infrastructure, documentation, etc.). Due to the open source code, it is also possible to make changes to the system without belonging to one of these Special Interest Groups (SIG), but then these may not be published under the brand “CentOS”. The individual SIGs have a certain degree of autonomy and are primarily responsible for the development process. Before the result can be marked and published as an official CentOS product, the approval of the Governing Board is required.

The three types of special interest groups declared are as follows:

  • Core SIG: Core SIGs develop content that is relevant to the major version of the Linux distribution. These groups must coordinate the development process with any RHEL updates and then take care of the signing and publication. They also need to develop guidelines for Git publishing for licenses and contributions.
  • Variant SIG: If the core of CentOS versions is to be modified or expanded independently of the official release series, this is done in Variant SIGs. A prerequisite for such a project is that it represents a concrete benefit for a group of the community. All additionally used software packages must conform to the licenses of the CentOS project and be able to be unpacked and issued appropriately. It is also the task of the working group to check additional code that has been written by other users for the respective variant and published via the Git repository and, if necessary, to include it.
  • Functional SIG: The Functional SIGs have the task of creating and managing important components of the CentOS project. The aim of these working groups is to make it as easy as possible for every interested user to participate in the further development. Furthermore, the purpose of these SIGs is to strengthen the community by distributing the responsibility and workload specifically among the active members according to their respective skills.

One of the most important working groups is the aforementioned AltArch SIG, which has already published various ports of the 7th CentOS version. The first real variant, however, is the CentOS Atomic Host published by the CentOS Atomic SIG. This is based on the core construct and is specially designed for the use of Docker containers. Other projects that are in the planning or development phase include the following:

  • Public CI: infrastructure for public tests
  • Hardening: Variant with a focus on a secure, hardened system core and source code
  • Cloud Instance: Distribution that CentOS-Linux optimizes for public or private clouds
  • PaaS: Platform-as-a-Service based on CentOS
  • NFV: Network Functions Virtualization provides a software stack that serves as the basic framework for the distribution and verification of virtual network functions
  • Promo: Working group that deals with the external presentation of CentOS

This is how the VPS CentOS installation works

To install the open source operating system on your own computer or VPS server, first download the appropriate port and variant from the official download center. In addition to the current releases, you will also find installation files and the repositories of older CentOS versions there. In the case of the images offered, which you have to transfer to CD, DVD or another portable storage medium such as a USB stick after downloading, there are also 3 different variants available to you in addition to the usual complete installation:

  • LiveCD: Such an image is bootable and provides a runtime environment that starts directly from the storage medium without the need for installation.
  • ServerCD: With this image you have an installable variant in hand, which is equipped with a limited package scope for server installations.
  • NetInstall: The NetInstall image, which in some cases is also listed under the designation “Minimal” in the download overview, enables you to carry out a minimalist network installation that is tied to the current release. For example, you cannot install version 8 with the NetInstall ISO from CentOS 6.2.

Once you have created the desired boot medium, start the CentOS installation directly from it. Simply select the “Install CentOS” button first and then confirm your selection with the [Enter] key. In the following you will be guided through the rest of the process with the minimal NetInstall variant by the graphical installation assistant. The English language and keyboard output is set by default, but both can also be switched to other languages.

CentOS Linux – a conclusion

When listing high-performance Linux descendants, CentOS is usually not one of the representatives that are directly mentioned first for virtual private servers. The distribution brings with it everything necessary for its target sector – in the server and enterprise area. So if you are looking for a stable system that you can use over a longer period of time, you won’t do much wrong with the RHEL modification. CentOS cannot offer the exclusive support of the commercial template and does not receive a certification for any software, as is the case with the Red Hat system. Thanks to the binary compatibility, however, various applications and security features also run on the open source system – which also offers the advantage of being completely free of charge.

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