How You Manage Debian Apt Sources Is Changing
There are poorly-communicated changes afoot in the world of
apt that affect how users of Debian-based Linux distributions will need to manage their third-party repositories (apt sources) and keys going forward.
On the bright side, these changes are actually for the better, and aren't something you need to take care of immediately. The pace of adoption will likely be quite slow, so it will be a while before they become mandatory.
But that said, if you're running Debian Buster (or later) or Ubuntu Impish (or later), it would be a good idea to spend a little time transitioning from the Old Way to the New Way the next time you find yourself with nothing to do.
This article will lay everything out for you, which should hopefully make it pretty easy. ;)
The first change affects how you define your apt sources.
The changes are more easily visualized than explained. Let's pretend you want to add apt-fast to your system.
The Old Way:
deb http://ppa.launchpad.net/apt-fast/stable/ubuntu impish main
The New Way:
Types: deb URIs: https://ppa.launchpadcontent.net/apt-fast/stable/ubuntu Suites: impish Components: main
Basically, instead of cramming everything into a single line in a
.list file, the new "Deb822" format wants you to break each bit out in a
(The root directory,
/etc/apt/sources.list.d, remains the same.)
All of the fields in the above example are required and must be present even if empty. For example, the Sublime Text repo doesn't have a defined "Component", so would need to look like this:
Types: deb URIs: https://download.sublimetext.com Suites: apt/stable/ Components:
As with the Old Way, you can combine multiple entries into a single file by leaving a blank line between definitions. But you might not even need to.
If, for example, you had your main Ubuntu sources in
/etc/apt/sources.list as follows:
deb https://mirrors.edge.kernel.org/ubuntu/ impish main universe restricted multiverse deb https://mirrors.edge.kernel.org/ubuntu/ impish-backports main universe restricted multiverse deb https://mirrors.edge.kernel.org/ubuntu/ impish-security main universe restricted multiverse deb https://mirrors.edge.kernel.org/ubuntu/ impish-updates main universe restricted multiverse
That could now be moved to
/etc/apt/sources.list.d/00-ubuntu.sources and written like:
Types: deb URIs: https://mirrors.edge.kernel.org/ubuntu/ Suites: impish impish-backports impish-security impish-updates Components: main universe restricted multiverse
(You don't need a main
/etc/apt/sources.list at all.)
00- prefix?" I hear one of you ask. Good question!
Under the new Deb822 arrangement, if two repositories happen to overlap each other, priority is automatically given to the first one loaded. The
00- prefix ensures these canonical entries are shoved to the top of the stack.
But wait, there's more!
There are a lot of different fields that can be added to the
.sources definitions beyond the four required ones. Some of them define additional repository options, like
Architectures, while others override
apt's default settings.
Here's the full list:
|URIs||Yes||One or more root URIs, separated by a space.|
|Suites||Yes||One or more suites or codenames, separated by a space.|
|Components||Yes||One or more components separated by a space. It can be empty, but must exist.|
|Architectures||One or more architectures separated by a space.|
|Languages||One or more languages separated by a space.|
|Signed-By||The fingerprint or keyring path to verify with.|
|Targets||One or more targets separated by a space. (Uncommon.)|
|Valid-Until-Max||Time in seconds to cache the indices.|
|Valid-Until-Min||Time in seconds to cache the indices.|
There are also a few dangerous options you should probably never use:
Migrating to Deb822.
Now that you know what the Deb822 format looks like, migrating is pretty easy.
All you need to do is rename each source in
[whatever].sources, open them in your preferred text editor, and transcribe the components from the single-line form into the Deb822 form.
If you still have a main listing at
/etc/apt/sources.list, that should also be moved into
/etc/apt/sources.list.d and given a
You can still comment out lines in a
.sources file with a leading
#, so if you want to give yourself a way back in case things go south, just comment out the original single-line entry until you're sure you've transcribed it correctly.
Afterwards, just run
sudo apt-get update to make sure all your sources are still being pulled and that nothing broke.
The next big change has to do with how users manage the public keys for their third-party apt sources. This change not only improves security and performance, but will also make it much easier to manage your keys going forward, so is well worth the effort!
apt-key has been deprecated, and its warning message contains a typo, so is no help at all. So what's the deal?
Basically, instead of adding a new key this way:
wget -qO- https://download.sublimetext.com/sublimehq-pub.gpg | \ sudo apt-key add -
You now need to add it this way:
wget -qO- https://download.sublimetext.com/sublimehq-pub.gpg | \ gpg --dearmor | \ sudo tee /usr/share/keyrings/sublimetext-archive-keyring.gpg >/dev/null
gpg --dearmor bit in the middle is only necessary for ASCII armored keys, but 99.9% of keys you'll find online are armored, even if they're incorrectly named with the binary
.gpg extension, as Sublime's is.)
One gotcha with the above is that the key needs to be owned by root, but readable by everyone else. If either of those don't happen, you'll need to fix it manually with:
# Fix the permissions: sudo chmod 644 /usr/share/keyrings/sublimetext-archive-keyring.gpg # Fix the ownership: sudo chown root: /usr/share/keyrings/sublimetext-archive-keyring.gpg
The key thing to note is that all third-party keys should now be placed in
/usr/share/keyrings, and they should all follow the basic naming pattern of
This is where the security improvements show up. The problem with
apt-key is that anything you add to it gets trusted globally, which isn't ideal. The
/usr/share/keyrings area, on the other hand, requires manual linking in the corresponding Deb822
.sources file, so can only be used for the repository it's supposed to be used for.
In keeping with the Sublime Text example, its source file should now be updated to read:
Types: deb URIs: https://download.sublimetext.com Suites: apt/stable/ Components: Signed-By: /usr/share/keyrings/sublimetext-archive-keyring.gpg
Signed-By field accepts either a path or a fingerprint, however if we're being honest, all fingeprints look the same, so for ease-of-maintenance, I'd recommend sticking with paths.
Migrating Apt Keys.
This is a three-part process:
- Every third-party apt source needs its own keyring under
- Each corresponding
.sourcesfile needs a
Signed-Byline pointing to its keyring under
- All non-distribution-owned keys need to be removed from the Old global keyring;
That non-distribution-owned qualifier is important. If the global keyring contains keys owned by Debian or Ubuntu, they were probably put there by system packages, and shouldn't be messed with! Haha.
So, what is the best way to go about this?
I would personally recommend pulling up the websites corresponding to each of your
.sources to locate their repository setup instructions.
If their sites mention a key fingerprint, like Ubuntu PPAs do, you can steal the existing key from the global keyring like this:
# Export and copy the key into place. apt-key export THEHEXFINGERPRINTGOESHERE | \ gpg --dearmor | \ sudo tee /usr/share/keyrings/THEREPONAMEGOESHERE-archive-keyring.gpg >/dev/null
THEREPONAMEGOESHERE to the appropriate values.)
If they just give you a straight link to the key instead, do this:
wget -qO- THEURLGOESHERE | \ gpg --dearmor | \ sudo tee /usr/share/keyrings/THEREPONAMEGOESHERE-archive-keyring.gpg >/dev/null
Once you've done that and verified the ownership/permissions as mentioned in the last section, add the corresponding
Signed-By line to the
.sources file, then run
sudo apt-get update to verify it is still fetching correctly.
Rinse and repeat until all your sources have been updated!
With that out of the way, all that's left to do is clean up the global keyring!
# List all keys. apt-key list # Delete each one (that isn't a Debian- or Ubuntu-owned key). # Repeat this over and over and over again. sudo apt-key del THEHEXFINGERPRINTGOESHERE
apt-key helpfully lists each fingerprint, but unhelpfully does so with spaces injected between the blocks. You'll need to manually remove that whitespace for the
apt-key del command.
But hey, once you've done that, you're done!
Or rather, after you run
sudo apt-get update one last time, you're done!
Once you've migrated all of your existing sources and keys, you'll just need to remember to ignore outdated instructions when adding new ones, and add them correctly. Haha.
For random third-party sites that give you the signing key, the process is no different than what we've already covered.
But Ubuntu PPAs will be a little annoying until they update their website or
add-apt-repository helper to work with the New World Order.
Let's take a look at apt-fast again as an example of how you can manually add a PPA in the meantime.
To fetch this key manually, you'll need to do a bit of bullshit. Look for the fingerprint (highlighted above), then:
# First, import it into your *personal* keyring. gpg --keyserver hkps://keyserver.ubuntu.com --recv-keys A2166B8DE8BDC3367D1901C11EE2FF37CA8DA16B # Now export it to the right place. gpg --export A2166B8DE8BDC3367D1901C11EE2FF37CA8DA16B | \ sudo tee /usr/share/keyrings/apt-fast-archive-keyring.gpg >/dev/null # And finally delete the copy from your personal keyring. gpg --delete-keys A2166B8DE8BDC3367D1901C11EE2FF37CA8DA16B
From there, you just need to create
/etc/apt/sources.list.d/apt-fast.sources, transcribing the single-line copy provided by the PPA page into the appropriate Deb822 format.
We didn't explicitly mention it earlier, but one neat trick with Deb822 is that it allows you to combine binary and source repositories into a single entry.
Most people don't use sources, but let's pretend that's what we want here. In that case, it would look like this:
Types: deb deb-src URIs: https://ppa.launchpadcontent.net/apt-fast/stable/ubuntu Suites: impish Components: main Signed-By: /usr/share/keyrings/apt-fast-archive-keyring.gpg
That's it! Run
sudo apt-get update once again and you should be off to the races!