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 * Make sure to remove 20-tum.conf and any unstable sources.list entry '''before''' testing is released as stable.  * If you are using the <<DebianCodename(testing)>> in your apt sources instead of testing, then you will switch to stable after the release of <<DebianCodename(testing)>>, so make sure to remove 20-tum.conf and any unstable sources.list entry '''before''' testing is released as stable.

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Debian Unstable (also known by its codename "Sid") is not strictly a release, but rather a rolling development version of the Debian distribution containing the latest packages that have been introduced into Debian.

As with all Debian release names, Sid takes its name from a ToyStory character. In the movie, Sid is the kid next door who breaks his toys and makes nasty creatures of them.

While other release code names progress in time from being "testing" to being "stable", Sid is forever doomed to being unstable. Sid will always be the unstable branch. When the current "testing" repository becomes mature and is released, "testing" becomes the latest "stable" release. From there, a new "testing" repository will be created with the next planned code name, and packages will continue to trickle down from Sid into "testing" just as before.

Sid is where packages go after they've been uploaded by their maintainer, and cleared for release by the FTP master. When packages have met certain criteria, they are automatically moved from Sid to the current "testing" repository. The "Unstable" repository is updated every 6 hours.

Sid exclusively gets security updates through its package maintainers. The Debian Security Team only maintains security updates for the current "stable" release.

The sequence of package propagation in the Debian development process is as follows:


There are no "unstable" full CD or DVD images. Due to the fact that the packages in "unstable" change so quickly, it is more appropriate for people to download and install "unstable" using a normal Debian FTP mirror.

If you are aware of the risks, choose one of the following ways to get set up on Sid:

  • Use the current "stable" installer to install a minimal stable system (recommended).

    • Change your apt sources to point to "unstable".

    • Run apt update and apt full-upgrade.

  • Use the current "testing" installer to install a minimal (next) stable system.

    • Change your apt sources to point to "unstable".

    • Run apt update and apt full-upgrade.

  • Use the Unstable "mini.iso" image.
    • Download the "mini.iso" for your CPU architecture located here: https://d-i.debian.org/daily-images/ under */daily/netboot/

    • During the installation choose "Advanced options" -> "Expert install".

    • In the step "Choose a mirror of the Debian archive" choose version "sid - unstable"

If you are already using a stable system use the method described above for upgrading to unstable changing your apt sources from "stable" (or the codename for the current stable) to "unstable".


What are some best practices for testing/sid users?

The most important thing is to keep in mind that you are participating in the development of Debian when you are tracking Testing or Unstable. This means that you should know your way around Linux, Debian, and the Debian packaging system.

There are a couple of things you can do in order to ease your life as a testing/sid user such as:

  • Consider (especially when using unstable) if you need to disable or remove unattended-upgrades in order to control when package updates take place.

  • Always be careful when you perform updates and check if the actions proposed by the package managing tools are in line with your wishes and expectations. (i.e. make sure that you do not remove a plethora of packages you need by blindly accepting the proposed action)

  • Choose the right time to upgrade: when you have time to investigate any potential issue, and after saving your work and doing backups - not before some business trip!
  • Use apt upgrade instead of apt full-upgrade to avoid unwanted removal of any packages that you depend on.

  • If a package cannot be upgraded safely put it on hold using apt-mark.
  • Install the apt-listbugs and apt-listchanges packages in order to be made aware of grave bugs or important changes when you install new packages or during an upgrade.

  • Automatically create daily, weekly and monthly backups in order to ensure that corrupted data is not a problem. It's extremely uncommon for an update to corrupt user's data but backups also protect you from drive failures and human errors.
  • Use a Copy-On-Write (abbreviated as COW) supported filesystem like btrfs or take advantage of LVM snapshots. Take snapshots before and after an upgrade. In case, if the system is in unrecoverable position, rollback to the last snapshot from a system rescue LiveCD. A useful program for this, as well as regular system backups is timeshift

  • Consider subscribing to debian-devel-announce@lists.debian.org (very low-traffic mailing list, 1 to 10 per month) to be notified on future technical changes or possible problems.

  • Keep a good live CD/USB such as Debian Live around at all times so you can still work on the system even if it is not booting anymore.

Does Sid have package "X"?

You can track the status of any package by using the Debian Package Tracker.

Is package "X" broken?

If it doesn't work for you, then there's a good chance it's broken. Your problem may either be unique to your system or experienced between several users. Because of this, Debian has a Bug Tracking System (abbreviated as BTS). Feel free to submit a bug report if you don't see your bug already there. Please read How to report a bug using reportbug and reportbug if you are unsure how to write a good bug report.

Can I use Sid packages on "stable"?

Trying to do so is highly discouraged. Attempting to mix packages between Debian repositories will likely create an unusable system. For more information about best practices, check out DontBreakDebian.

If you wish to use newer software, it is best to install packages from Backports.

Can I use Sid packages on "testing"?

Yes, with some care. This is referred to as a "Testing-Unstable Mix". Configuration is required to ensure a testing system stays on testing, without apt upgrading every package to the unstable version.

First, create /etc/apt/apt.conf.d/20-tum.conf with these contents:

APT::Default-Release "/^testing(|-security|-updates)$/";

Then, edit /etc/apt/sources.list and copy one testing line to unstable, for instance:

deb https://deb.debian.org/debian testing main
deb https://deb.debian.org/debian unstable main

Run apt update to refresh the cache. Use apt -t unstable install foo to install package foo from unstable rather than testing.


  • Synaptic (and possibly other gui package frontends) ignores the Default-Release setting. Set in Preferences->Distribution.

  • If you are using the trixie in your apt sources instead of testing, then you will switch to stable after the release of trixie, so make sure to remove 20-tum.conf and any unstable sources.list entry before testing is released as stable.

  • If the dependencies of the packages you're trying to install from unstable aren't satisfiable in testing, they'll be installed from unstable. This may cause you to see dependency conflicts with other packages, especially if you install a package from unstable that's involved in a library transition.

Where can I get help with Sid?

You can get help in the #debian-next channel on OFTC and on the mailing lists.

See also