July 21 2019

Difference between CentOS, Fedora and RedHat RHEL, AlmaLinux. When to use them and in what context? (Updated to 2022)

A comprehensive explanation of which Linux distribution you should use and why.

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The largest open source company working with Linux is today Red Hat. She is known for her contributions to many open source projects, including the Linux kernel itself. Less well known is that Red Hat is involved in several Linux distributions, directly or indirectly.

Essentially it can be very sparsely summarized that Fedora is Red Hat's gym and CentOS is (or rather it was up to version 8) the Red Hat clone without commercial support and Red Hat assistance.

All three distributions essentially enjoy very common characteristics on the technological and software side, however from an especially entrepreneurial point of view, choosing one distribution rather than another can produce positive and negative effects that are also very important from the point of view of civil liability. or even penalties.

Who should install what? In what context? With which pros? With which against? What limits and what freedoms? These are apparently stupid questions that instead deserve to be faced with hypothetical scenarios that we have already adopted in almost 15 years of career.

Let's first see the "technical data sheets" of the respective Linux distributions that can help you better understand the individual ones in order to then continue with a healthy comparison.


Fedora

 

Fedora has received many individual updates and releases over the years. It's a playground for new features. New technologies are often found and tested here. It can be compared to other distributions such as Arch Linux, except it is slightly less aggressive in distributing the latest software components for everything.

  • Community driven
  • Short release cycles (6 months)
  • Focus on features and new technologies
  • Very commonly used on the desktop

The difference between Fedora and other distributions is Red Hat business support (to the distribution and not to the end user). This means that professional developers can work on projects that are being tested for the first time in Fedora. Many of these components can therefore also be collected from other distributions. It also powers the RHEL product. Everything that is considered stable and useful for the most demanding companies, can be moved in successive stages towards distribution Red Hat RHEL.

Who should or shouldn't use it?

With very fast release cycles and very short unofficial supports, you risk investing time and resources on the installation of systems that are then outdated after a few months, making it impossible to guarantee lasting stability with relevant updates, patches and security. of systems but above all enterprise environments.

Fedora is fine to be installed on developer or consultant desktop systems, home systems and end-user systems. It is good to be installed on staging systems in which to test the new features of new software and / or new kernels.

It is good in any context where you don't need guaranteed software stability, where you don't need certified solutions and / or Red Hat certified developers, systems engineers or technical personnel.

Assistance and support

The assistance must be delegated to third-party consultancy companies or internal staff of the company with the awareness that for any problem, even serious, you will not be entitled to any commercial support from anyone and that there are no license agreements with relative civil liability. or criminal.

Absolutely not recommended for Hosting Providers, SMEs, Banks, Public Administration, Insurance companies or companies in general that need long-term support at least for the release cycles and even minimal guarantees if not contractual at least in terms of stability and duration. .

If you want to delegate professional assistance to certified technical personnel, a Red Hat certification may be an entry requirement for any open job positions. However, talking about job positions, Red Hat certifications in a context that is little more than an amateur Fedora user, leaves the time he finds.

Software updates and versions

This Linux distribution is always very advanced, both for the release of the packages that accompany it and for the release of the Kernel with which it is equipped.
To be clear while we are writing the version of the Kernel supplied with Fedora (Fedora 30) is 5.0 compared to version 3.10.0-957 of RHEL 7.6 release.
Wanting to be meticulous and to participate in the comparison even the very recent RHEL 8.0 released just 2 months ago, it is supplied with the Kernel 4.18.0-80.

Moreover, Fedora also allows on a practical level to have numerous external third-party RPM repositories such as that of REMI, ELREPO, and so on, allowing you to install RPM packaged software from third parties through the yum utility that actively contribute to maintaining high availability of more varied software packages, keeping them compatible with the world of RPM packages from Red Hat.

What about security?

Fedora's security normally follows RHEL's trends although especially for important and imminent vulnerabilities (the classic 0days) the upgrade and patch release follows a slightly slower course than that of RHEL which is in fact the first company to take action and release patches when there is a critical vulnerability to their software and distributions.

 


 

Red Hat Enterprise Linux (RHEL)

 

Red Hat's Linux Enterprise distribution is called RHEL for short. The main difference with Fedora is that focuses on companies that prefer stability. The most critical services for businesses are distributed on this platform. Components tested in distributions like Fedora may finally end up in this distribution.

  • Focus on stability
  • Supported by Red Hat
  • Paid license
  • Common on the server

For companies that rely on the stability of a Linux distribution and related commercial support directly from the parent company, you may want to use this distribution.

Who should or shouldn't use it?

On an entrepreneurial level all those who need to have a certified software solution that falls within the famous "choice of the market", that is the choice they have made, or would make leading companies in the sector or compatible with ours.

More than a RHEL product, it should be perceived as a service which allows you to direct a business towards a certified platform such as RHEL and certified assistance always both RHEL and through the parent company itself and through technical personnel certified by the various RHEL certifications that guarantee (at least on paper) the preparation and knowledge of Red Hat Enterprise Linux RHEL to the user who has decided to train and pass certification exams to obtain an internationally recognized certification.

Red Hat Enterprise RHEL is the ideal solution for Banks, Insurance, Public Administration, SMEs and essentially companies that need to have guarantees at least in the choices made at a managerial level and in the decision-making process, Red Hat Enterprise Linux is the right choice to be able to justify one's choices and relieve itself from potential problems inherent in the choice of software having in fact chosen the best partner on the market.

To be very direct, no administrator of any company or IT manager could be questioned if there may be a problem with the operating system itself, having chosen the best solution on the market and recognized as such.

On the other hand, it is not a solution recommended for individuals, the hobbyist and the companies that have it very low server revenue limited such as those for example of Low Cost Hosting, where they could easily use solutions such as CentOS which offers a lot of freedom at practically no cost.

Assistance and support

The assistance must be delegated to third-party consultancy companies or internal personnel with the possibility of subscribing to a support subscription directly with Red Hat.

The cost of support directly from Red Hat varies from the type of assistance you need but this support should not be seen as a replacement for external consultancy companies or internal systems engineers, but rather as a coaching that can be used in extreme cases when for example runs into absolutely rare issues and needs undocumented support procedures.

The types of support offered in combination with the distribution are: self support (i.e. without RH support), Standard and Premium, with very different characteristics and costs respectively of $ 349 for self support, $ 799 for standard and $ 1299 for premium. Annual passes means. The features are instead the following as described on their website.

RHEL licenses

All companies that decide to adopt a RHEL distribution within the company should also be advised to have one or more RHEL certified systems engineers in the company or, if necessary, to have the current ones certified in order to have perfectly compliant and compatible systems and systems.

It is worth remembering at least for information purposes only that the possession of a Red Hat certification (although in some cases it can be perceived only as a mere badge), in many realities such as those of large companies, multinationals and big corporations such as those in TOP FORTUNE 500 gives you many more chances to be noticed and hired with a really advantageous salary.

 

Software updates and versions

This enterprise-grade distribution has its strengths in stability and long-term support.
Precisely because of this enormous advantage, obsolescence problems can occur in some packages that are not updated to the latest versions.

In fact, at the time we are writing packages such as Apache, NGINX, PHP and OpenSSL are not updated in the Web field, causing tangible problems such as the lack of HTTP / 2 with ALPN support, a modern PHP interpreter such as 7.2, the lack of a modern Kernel such as 4.18 or later that supports high performance based congestion control TCP BBR rather than the now prehistoric CUBIQ11.

As reiterated for the Fedora description while we are writing the version of the Kernel supplied with Fedora (Fedora 30) is 5.0 compared to version 3.10.0-957 of RHEL 7.6 release.
Wanting to be meticulous and to participate in the comparison even the very recent RHEL 8.0 released just 2 months ago, it is supplied with the Kernel 4.18.0-80.

Although as we wrote for Fedora also on RHEL there is the practical possibility of having numerous external third-party RPM repositories such as that of REMI, ELREPO, and so on, it must be said that the adoption in production of similar repositories, although absolutely excellent in the practice, theoretically they can go to invalidate that security of software exclusively authorized by Red Hat, and therefore many managers, IT managers, and many corporate policies strictly prohibit the use of these alternatives very practical, fast and functional more for bureaucratic reasons than for anything else.

It is clear that if you want to adopt a company policy based exclusively on Red Hat certified software, or you give up some features, or you have to recompile from source code, this is an optimal practice from a purely bureaucratic point of view but often with problems. potentially large and not exactly short times.

If, on the other hand, you want to opt for the use of third-party external repositories that are not Red Hat certified, one wonders whether at this point it is no longer profitable, even at an economic level, to directly adopt a Enterprise clone distribution such as CentOS which we will see later.

What about security?

RHEL's security inherent in patch release processes is very fast especially on subscription channels like RedHat Channel. It must be said that RHEL is the first of the three distributions to distribute patches for severe vulnerabilities especially when there are 0days with potentially severe impact.


CentOS

CentOS is a derivation of RHEL. It is based on the exact same basic code. It has recompiled all the source packages it contains, effectively making it a very similar if not nearly identical system. The Red Hat logos that are their property have been replaced with the Linux CentOS logo.

CentOS is great if you like the stability of RHEL and want to significantly reduce costs since in fact it is absolutely free as well as Open Source.
As this has no official support from Red Hat which in fact as anticipated above offers commercial support only on Red Hat Enterprise RHEL.

  • Based on Red Hat Enterprise RHEL
  • Community driven
  • Focus on stability
  • Free

This option could be less suitable for business-critical services as it is not officially supported by Red Hat. Even if you prefer recent software packages, CentOS (such as RHEL) may not always be the best option, although there are solutions that we will see later.

Who should or shouldn't use it?

In 2022 as we will see below, CentOS is not recommended in production. If you are looking for a stable, Enterprise system with LTS support, CentOS has been brilliantly replaced by AlmaLinux.

Everything you will read below, the praise towards the Linux CentOS distribution has been exclusively referenced up to version 7 (included). If you are using CentOS 8, you are welcome to migrate to AlmaLinux.

To date (2022 year in which we write this article) CentOS has no reason to be taken into consideration at all except to be updated and migrated to AlmaLinux.

At an entrepreneurial level, any small / medium enterprise that does not have an adequate business model to obtain a sufficient return on investment from adopting an enterprise distribution such as Red Hat RHEL.

Anyone who still needs a perfectly equivalent technological product without having the support of the parent company or any type of support subscription can and must use CentOS as a replacement for RHEL.

Although we tend too often to minimize the importance of a distribution like RHEL given the existence of the CentOS equivalent, let's also remember for correctness that CentOS was born from a recompilation of the packages of the commercial distribution RedHat Enterprise RHEL and not the other way around, which is why It is easy to understand that without RHEL and all the above work by RedHat engineers not even CentOS would exist.

It is good for use in the academic, scientific, university, hosting provider and even enterprise environments of any size, although it is very difficult to see it adopted in corporate or large-scale reality.

In fact, no administrator would accept to adopt a software solution that comes from the spirit and goodwill of a community and not of a company that conforms to the highest standards of quality and responds to that "unwritten law" that at certain levels large companies make agreements and commercial deals between large companies in fact.

Most of the commercial Linux hosting that you find on the net, however, are based on CentOS, therefore a sign of the absolute goodness of the product, but with a non-corporate policy (it is not a company) that makes it inadequate for the large entrepreneurial realities mentioned above.

To be clear, a manager of a multimillion or billionaire company will never accept not having direct support from the software developer, which is why he will prefer to spend tens of millions on software licenses and updates and feel relieved of responsibilities that in some contexts are absolutely important.

Update 2022: Considering the upset of the balances derived primarily from the acquisition of RedHat by IBM and the subsequent change in the licensing method of RHEL and the relative support of CentOS which has resulted in a radical change with CentOS Stream making the CentOS distribution starting from release 8, a distribution profoundly different from RHEL, effectively missing LTS support, and the stability of the packages, CentOS is not recommended in any way and is instead recommended to upgrade to the new AlmaLinux of which you can read more at this link: AlmaLinux is the new LTS alternative distribution to RedHat RHEL 8 and CentOS 8

Assistance and support

The assistance must be delegated to third-party consultancy companies or internal staff of the company. There is no support from Red Hat.

Also in this case, when hiring qualified technical personnel in the IT field, a RHEL certification is absolutely welcome and a trump card.

The RHEL training obtained during the certification phase will be spent exactly on CentOS without any problem as the two systems are practically identical.

Software updates and versions

As mentioned for RedHat RHEL, this enterprise-grade distribution also has its strengths in stability and long-term support.
Precisely because of this enormous advantage, obsolescence problems can occur in some packages that are not updated to the latest versions.

In fact, at the time we are writing packages such as Apache, NGINX, PHP and OpenSSL are not updated in the Web field, causing tangible problems such as the lack of HTTP / 2 with ALPN support, a modern PHP interpreter such as 7.2, the lack of a modern Kernel such as 4.18 or later that supports high performance based congestion control TCP BBR rather than the now prehistoric CUBIQ11.

As reiterated for the description of Fedora while we are writing the version of the Kernel supplied with Fedora (Fedora 30) is 5.0 compared to version 3.10.0-957 of the 7.6 release of RHEL and CentOS.

At the time of writing, the latest release of RHEL, version 2, has been out for 8 months now. CentOS, on the other hand, has not yet come out with version 8, although as seen in previous editions (which you can see in the following table), more than a couple of months have never passed since the release of the respective CentOS release once the RHEL version has been published .

As mentioned for Fedora and also for RHEL, CentOS also has the possibility of using external repositories. Normally in the areas where CentOS is used there are no strict and stringent rules that entail the absolute prohibition of the use of non-certified repositories since CentOS itself is a non-certified linux distribution with only a community behind it.

This greater lightness, beyond the complex bureaucracy that dutifully reigns in some production areas, allows a speed of intervention and updating of packages being able to be very fast and effective in the implementation of new features, installation of new software or upgrades of new kernels.

Always to be clear, the installation of a 5.0 Kernel on CentOS using the ELRepo repository takes only 3 commands and about 60 actual seconds, avoiding dangerous virtuosities of kernel recompilation and installation which, although they are the standard purist practice, are absolutely misleading in an environment production where perhaps you need to update 200 machines in one night.

What about security?

Derived from RHEL, CentOS security inherent in patch release processes is very fast but slightly slower than RHEL. Normally in case of serious problems the relative patch on the CentOS update channels is released with 24/48 hours delay compared to RHEL, which is why in any case in mission critical areas it is always recommended to use RHEL when possible.


Conclusions

Having summarized as best we can the relative substantial differences between the three RPM Based distributions, it would be appropriate at this stage to brutally eliminate Fedora from games, which as we have seen is nothing more than an environment suitable for experimenting with new features and oriented above all to the Desktop rather than to servers.

Remain RHEL and CentOS AlmaLinux (since 2022 CentOS has no longer any reason to exist and has been replaced by the excellent AlmaLinux), and at this point the question which to choose is brazenly answered with another question: "How much money do you have ?"

Because if it is true that RHEL is very nice, functioning, enterprise and already at the time of purchase it makes you feel pampered by that feeling that you are in an iron barrel, it must also be said that this is not always the case and that above all buying RHEL has a its cost.

Although the pricing you see on the site is absolutely negotiable especially for a large number of licenses and that you could get to pay it even discounted 80% on certain volumes, it is also true that it still has its considerable cost and its undoubted advantages.

Can you see a local health company installing CentOS because it doesn't have the money to buy RedHat? In a third world company perhaps (and CentOS is welcome for them) but not in "our world" that we know.

Do you see a bank installing CentOS rather than RedHat to save a few tens or hundreds of millions of dollars? Perhaps in science fiction but not in the real world as witnessed by Deutch Bank itself or Lufthansa.

 

In short, in a perfect world every Linux user on a professional level would buy RedHat which is the best solution on the market and the best strategic partner. However, they do not always have the numbers, the resources and a business model to support a similar expense and therefore a compromise is reached.

If we take the example of many of our customers who have an average cost of about 300 euros per month for a managed dedicated server, for a total of about 3600 euros a year, what tangible advantage would they have in increasing the cost of 1200 euros. the year (or 50%) if you actually only need a well configured web server with the exact same software that you would also find on Red Hat? Probably nothing.

But if our client was not some blog with a few tens of millions of unique visitors per month but a chemical company certified with the highest ISO standards and the administration regardless of a certified linux distribution such as RHEL because it wants and expects the best. solution of the market, sure that those 1200 euros a year more would not change anything from the point of view of the budget but would still give the company that "something more" not obtainable with CentOS?

It is therefore right that every company that has a forward-looking and modern vision, with the economic resources to sign RHEL licenses, is at least informed about the possibilities it would have in buying Red Hat rather than CentOS, certain that many administrators of virtuous companies have that determination to make the best choice in their own interests and that of their company.

In all other “I wish but I can't” cases, we also use CentOS which has all the goodness of RHEL with no support costs and contributes significantly and tangibly to helping small businesses around the world.

Do you have doubts? Not sure where to start? Contact us


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