Most of us experience Linux through the filter of a distribution. The exceptions are those who build their operating system from source files – there is even a project called Linux From Scratch to help that hardy minority. However, like most free software, distributions are hard to track. Many offer download statistics, but often one user does multiple downloads. The only data available is the statistics offered since 2001 by Ladislav Bodnar's DistroWatch site [1]. It is not a precision instrument, since distributions can take some time to appear on the site for one reason or the other, but it is the best we have. Accordingly, every year or so, I like to scan the site to see what trends I can tease from its pages. I mainly see a growing centralization over the last decade, although a few minor trends are also visible.

DistroWatch lists 418 distributions. Of these, 275 are active in 2020, a small decline since 2014, when 285 were active, and a larger decline from the 323 in 2011. Today, 55 are listed as dormant, which means that someone somewhere might consider reviving them at some point, while 88 are officially discontinued. Overall, just under two-thirds of all distributions ever released continue to update. Of those, only 15 are BSD, while 4 are Solaris. The rest, of course, are Linux.

The reason for this decline is probably the dominance of a handful of large distributions, particularly Debian. The dominance is clearly seen in the list of page hits each distro receives on DistroWatch. These hits only represent popularity among DistroWatch's readers, but the top 10 results seem likely to approximate the popularity among all Linux users (Figure 1). In the last decade, Ubuntu, Fedora, Mint, and Debian have been consistently in the top 10, the only difference being the exact order. Debian consistently hovers around fifth, and Mint somewhere between first and third, but others vary. A decade ago, Ubuntu was consistently first while it was focusing on its desktop. However in 2020, with its move away from desktop development, Ubuntu has slipped to fourth. One thing has been consistent in the last decade: At least 4 of the top 10 distros have been Debian, and sometimes as many as 6. Debian's dominance is even stronger in page hits, with 11,139 for Debian and its derivatives, and only 5,012 for other distributions.

Figure 1: Page hits on DistroWatch are not an exact metric, but they do suggest which distros interest users.

Meanwhile, openSUSE currently has slid to 12th place, while Manjaro has entered the top 10 in the past few years. More recently, Pop!_OS and elementary OS (two Debian derivatives) have also entered the top 10. Farther down the top 100, once-popular expert distros like Slackware, Gentoo, and Arch have slid down the list. By contrast, aesthetic-focused distros like deepin and Zorin have also slid from the top 10, but hover just outside it.

Plying the Search Field

The link to DistroWatch's Search page [2] is hidden in its homepage header. It is intended to help users choose a distribution and includes the ability to track the releases of packages in distributions. However, more relevantly, it also gives a rough indication of preferences and technological trends (Figure 2).

Figure 2: DistroWatch's Search page not only helps users decide between distros, but it also indicates some of the current trends.

After the list of page hits, a place to begin looking at on the Search page is the Based on field. Right away, the field gives proof of Debian's importance by allowing searches based on the Stable, Testing, or Unstable repositories, a feature not given for any other distribution. A search for distributions based on Debian returns 121 results, with 8 based on Testing and 1 on Unstable. While Linux users are sometimes assumed to care most about the latest releases, these numbers suggest that for many users the priorities are what Debian Stable is best known for: stability and secure and timely updates.

A search for distros based on Ubuntu, Debian's most popular derivative, returns another 55 results. Derivatives of Mint, Knoppix, and other derivatives might add another 10 or so. In other words, just under two-thirds of active distributions are first- to third-generation Debian derivatives. No other distribution comes even close to this percentage. Even Fedora, which two decades ago rivaled Debian in popularity, has only 26 derivatives, and then only if CentOS and Red Hat Enterprise Linux's derivatives are counted in Fedora's tally. Other derivatives tend to be based on expert distros, like Arch (21), Gentoo (8), or Slackware (7), often simplifying installation and configuration. Although the market for these derivatives may be small, there is still enough interest to continue their existence. In comparison, only 61 distributions are listed as independent (i.e., not a derivative).

Social and Hardware Trends

According to DistroWatch, distributions are developed in 74 countries. However, they remain primarily a phenomena of the United States (76) and Western Europe (80). However, given online development, the country of origin is not as important as it might be in conventional development. The bias is also lessened by 72 different locales and languages.

The site lists 30 different distribution categories. Of these categories, 158 distributions are listed under Desktop, which seems to mean general purpose, followed by 64 for Server, and 23 for Security. Other well-represented categories are Old Computers, Beginners, and Education, each of which is represented by 14 distros. Continued interest in Raspberry Pi is shown by 30 distros that support it, as opposed to a single distro for Android.

These listings also suggest several trends in development. For instance, 234 current distributions have fixed releases, in which the entire distribution is updated in a general release, whereas 48 have rolling releases, in which packages are updated individually rather than altogether. Some of these rolling releases, like Arch Linux, are entirely rolling, while others, like openSUSE, issue both fixed and rolling releases. Since fixed releases are potentially more secure, while rolling releases are more current, which one your distro supports can be a major concern. Similarly, 15 distributions support Long Term Support (LTS) releases, which are supported for longer than standard releases, making them of interest to corporate users.

Another issue that can be tracked on DistroWatch is support for UEFI Secure Boot [3], a verification system to ensure that only secure code runs a system; this has been a growing concern for several years. Although it does not affect older computers, Secure Boot is oriented towards Microsoft operating systems. When first introduced, it had to be disabled – if possible – to run Linux. However, a growing number of distributions use shim, which (as its name suggests) stands between other operating systems and Secure Boot. Instead of requiring Secure Boot to approve a variety of operating systems, it need only approve shim. DistroWatch includes a search for which distros install shim and which version they support. The list includes not only major distributions like Ubuntu and Fedora, but a growing number of lesser-known ones as well – a total of 46 altogether, with this number slowly increasing as a former hardware issue becomes simply another consideration.

Perhaps the most important issue that can be tracked is the use of systemd [4], the elaborate init system for starting and managing systems. Ask around, and most people who use Linux are apt to assume that systemd has more or less become standard in distros, making the controversy over whether to use it a dead issue. However, DistroWatch's search features soon suggest otherwise. Interest in alternate init systems is strong enough that during the last year or so DistroWatch has had a special search for them – a search that returns 102 distributions. Many of these distributions are minor, or, like Devuan, consciously in revolt against systemd, but the results also include popular distributions like MX Linux, Knoppix, and PCLinuxOS. You can also search based on particular init systems. Apparently, the debate over systemd is not over yet.

Larger Trends

Free software's values include diversity and choice. However, while still healthy, these values appear to be in decline over the last decade, with the number of distros declining by 15 percent. Even more significantly, mainstream Linux has become increasingly synonymous with Debian. Although a crisis is still distant, it appears that free software has less to congratulate itself on than most of us assume.

Whether this loss of diversity will continue is anybody's guess. Some of the development trends, like the increased interest in non-systemd inits, suggest that diversity can re-emerge even after an issue appears to be resolved. But there is still enough diversity that little is certain. The information DistroWatch collates to help users choose their distros is not an exact mirror of trends, although it suggests more than might be expected. While imperfect, DistroWatch offers one of our few glimpses into the current state of distributions.