Like most other Linux distributions, Debian gives a specific name to its latest stable release. Since July 6th, 2019, Debian stable is named Debian Buster. However, what distinguishes Debian from most other Linux distros is that it also provides the testing and unstable versions of its operating system. Debian Bullseye (testing) and Debian Sid (unstable) are thus readily available to Debian users before the devs officially release them as the stable version. Here’s how it works:

The Debian releases cycle: How it works

Picture of the Debian logo and slogan
Picture courtesy of the Debian Wiki (
  • You have your standard Debian stable release, an OS which is highly secure and extensively tested, but slightly outdated as a result. Debian stable is the preferred operating system for those using older computers or those new to Linux. It provides a high level of OS stability to those who might be uncomfortable with the troubleshooting inherent with the use of more unstable Debian versions. Because of the time involved in ensuring long-term stability, the core components of Debian have been designed for hardware released a while ago. As such, it is not unusual to find out that this version is only compatible with older peripherals and possibly the most common current ones.
  • Such a high level of testing, security, and stability require the use of the operating system over an extended period to catch as many potential bugs as possible. That is where Debian Testing and Debian Unstable come in. To ensure that as many users as possible can try out and test the future stable release of Debian, the developers will release its next stable version ahead of time. Whereas Debian Buster is now considered the current stable release, at the time of its inception, it was an unstable version.
  • Before being released as the stable version of Debian, Debian Buster was the testing version while Debian Bullseye was unstable. The now obsolete Debian Stretch was the stable version of Debian until recently. Debian Buster remained in testing until it was considered ready to replace Debian Stretch completely. With the latter changing from testing to stable and Bullseye changing from unstable to testing, the Debian devs added a new unstable release: Debian Sid.

As you can see, whenever a version of Debian is an official stable release, it has already seen many years of community-driven testing and usage. As of October 2019, Debian Bullseye is the new stable release (since July 2019). Judging by the usual timeline of approximately two years per stable release, we can assume that sometime in 2021 it will be replaced with Debian Bullseye. By then, Sid will thus become the testing release. Another Debian release (TBA) will then become the new unstable version.

Each Debian release has thus a full release cycle of five years (plus an additional five years of Long Term Support for the official stable release). It spends three years as the unstable version, two years as the testing release and then becomes the official Debian release. 

So, which Debian release should you choose?

Debian Buster (stable) vs. Bullseye (testing) vs. Sid (unstable)

  • Debian stable: Debian 10.1 Buster (as of September 7th, 2019; moved from testing to stable)
  • Debian testing: Bullseye (moved from unstable to testing on July 6th, 2019)
  • Debian unstable: Sid (announced in 2018)

Debian Buster

If you are brand new to Linux, you might want to consider Debian stable. If you are unsure whether or not the stable release is compatible with your current hardware, I suggest trying it out first using a virtual machine. Furthermore, consider downloading the unofficial disk image containing nonfree firmware rather than the standard official ISO file. The use of the nonfree packages ensures that Debian will detect most peripherals, including recently manufactured ones. An advantage of the stable release is that it guarantees “3 years of full support for each release and 2 years of extra LTS support.”

Debian Bullseye

If you are somewhat tech-savvy or aren’t afraid to use the many Linux resources available (LINK), then I recommend installing Debian testing. That is especially the case if your favorite software applications are not available on the stable version of Debian. Indeed, because many apps “evolve” to meet the requirements of more advanced OS and firmware, this Debian release might be too old to support them. To make the stable version compatible, you will need to add backports. Or…you can get Debian unstable, which automatically includes ports that allow the installation of apps requiring newer technology. Using backports every once in a while to install specific apps on Debian stable is not a problem in itself. However, it can quickly become one if you end up relying on backports whenever you want to add a new package. Doing so enhances the risks of bugs and package compatibility issues, and isn’t part of Linux’s best practice. That is why I recommend Debian testing if you plan on using many recently-developed apps. 

If you like the stability provided by Debian Buster but are using a relatively new computer, then I strongly recommend using the testing release nonetheless. The reason for sticking to the testing release is that by installing Debian Buster on a new computer, you risk having to install several additional packages. In addition to the nonfree ones used for firmware compatibility, you might need to install several packages from the testing or unstable releases using backports. That, in turn, can result in what is commonly called a “Frankendebian.” That is, an operating system that ends up being a mix of different releases. For instance, you might get an OS that uses a stable kernel with testing peripherals drivers or library packages. That system configuration will then cause you issues when it comes time to upgrade your system. In itself, a “testing” operating system isn’t unstable. That is particularly true of Debian Bullseye, as it has already been through three years of testing. 

Picture of Frankenstein with the words "franken debian" written over it.
Representation of the dreaded Frankendebian. Picture courtesy of debiman (

Even if you aren’t that familiar with Linux troubleshooting, you can find online forum threads about most if not all potential issues. Thus, it is almost a guarantee that you can find a troubleshooting solution to virtually any problems, as long as you are using a mainstream computer brand. 

Debian Sid

Generally speaking, I wouldn’t recommend installing Debian unstable unless you really know what you are doing. The Debian community relies heavily on users testing this version for the developers to fix potential system-breaking issues. Consequently, using Debian Sid is best left to those already familiar with Debian and troubleshooting in general. However, if you… 

  • Are comfortable with Linux
  • Regularly back up your system
  • Aren’t afraid of updates which will inevitably at some point “break” your OS for a while, and…
  • Want to give back to the community

…Then using Debian unstable and sharing the bugs you encounter (and ideally how you fixed them) with the devs is invaluable. After all, without people testing Debian unstable, we wouldn’t have this remarkable unstable → testing → stable system, and Debian wouldn’t be what it is now.

As a side note, if you are wondering why the different Debian names ring a bell, here’s why: They are all inspired by characters from the Toy Story universe. The more you know!

A picture representing a character of Toy Story. Debian Buster, Bullseye and other releases have names which are all inspired by the Toy Story universe.
Photo by Zakaria Ahada on Unsplash
Owner and content creator behind Geeky girl and blogger based in Montreal, Canada. Chocolate and nature lover (in that order). View all posts by Larryssa →

1 Comment

  1. Sid is always the same as unstable. Sid has not been created in 2018, either. Some time after Bullseye becomes stable, development will start on a new testing release (Bookworm). Sid will remain the unstable “release”.

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