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Configuring Apt Sources

Apt downloads packages from one or more software repositories (sources) and installs them onto your computer.

A source can be the official Debian Stable repository, an additional Debian repository such as Debian Backports, a local CD/DVD/directory, or a custom network/web/FTP server.

Editing sources directly

You can edit the file which determines your sources directly using your favorite text editor. This example uses nano:

nano /etc/apt/sources.list

You should read the manual for this configuration file first here or by typing man sources.list at a console window. You could also read the sources.list wiki page.

Using a graphical program

Some programs allow configuring Apt sources through a graphical interface. For example:

/etc/apt/sources.list

As part of its operation, Apt uses a file that lists the 'sources' from which packages can be obtained. This file is /etc/apt/sources.list.

The entries in this file normally follow this format (the entries below are fictitious and should not be used):

deb http://site.example.com/debian distribution component1 component2 component3
deb-src http://site.example.com/debian distribution component1 component2 component3

Archive type

The first word on each line, deb or deb-src, indicates the type of archive. Deb indicates that the archive contains binary packages (deb), the pre-compiled packages that we normally use. Deb-src indicates source packages, which are the original program sources plus the Debian control file (.dsc) and the diff.gz containing the changes needed for packaging the program.

Repository URL

The next entry on the line is a URL to the repository that you want to download the packages from. The main list of Debian repository mirrors is located here.

Distribution

The 'distribution' can be either the release code name / alias (jessie, stretch, buster, sid) or the release class (oldstable, stable, testing, unstable) respectively. If you mean to be tracking a release class then use the class name, if you want to track a Debian point release, use the code name. Avoid using stable in your sources.list as that results in nasty surprises and broken systems when the next release is made; upgrading to a new release should be a deliberate, careful action and editing a file once every two years is not a burden.

For example, if you always want to help test the testing release, use 'testing'. If you are tracking bullseye and want to stay with it from testing to end of life, use 'bullseye'.

Component

main consists of DFSG-compliant packages, which do not rely on software outside this area to operate. These are the only packages considered part of the Debian distribution.

contrib packages contain DFSG-compliant software, but have dependencies not in main (possibly packaged for Debian in non-free).

non-free contains software that does not comply with the DFSG.

Example sources.list

Below is an example of a sources.list for Debian 10/Buster.

deb http://deb.debian.org/debian buster main
deb-src http://deb.debian.org/debian buster main

deb http://deb.debian.org/debian-security/ buster/updates main
deb-src http://deb.debian.org/debian-security/ buster/updates main

deb http://deb.debian.org/debian buster-updates main
deb-src http://deb.debian.org/debian buster-updates main

If you also need the contrib and non-free components, add contrib non-free after main. For example, for Debian 10/Buster:

deb http://deb.debian.org/debian buster main contrib non-free
deb-src http://deb.debian.org/debian buster main contrib non-free

deb http://deb.debian.org/debian-security/ buster/updates main contrib non-free
deb-src http://deb.debian.org/debian-security/ buster/updates main contrib non-free

deb http://deb.debian.org/debian buster-updates main contrib non-free
deb-src http://deb.debian.org/debian buster-updates main contrib non-free

If you also need the Backports, contrib, and non-free components, add buster-backports lines. For example, for Debian 10/Buster:

deb http://deb.debian.org/debian buster-backports main contrib non-free
deb-src http://deb.debian.org/debian buster-backports main contrib non-free

You can instead use https://... in all of the above lines to use the repositories over encrypted HTTPS connections if the according mirror supports HTTPS. (Users of Debian 9/Stretch or older releases will need to install the apt-transport-https package first. The security.debian.org hosts currently do not have publicly verifiable SSL certificates on HTTPS and hence cannot be used with HTTPS at the moment.)

You can use a GNOME tool to edit your sources.list file. Access it through Menu → System → Administration → Software Sources.

gksu --desktop /usr/share/applications/software-properties.desktop /usr/bin/software-properties-gtk

Using Tor with Apt

Apt can retrieve and download updates through Tor. For this to work you need to install the tor and apt-transport-tor packages. You can then use the official onion services provided by Debian.

Here is an example sources.list using the onion services for Debian 9/Stretch:

deb tor+http://vwakviie2ienjx6t.onion/debian stretch main
deb-src tor+http://vwakviie2ienjx6t.onion/debian stretch main

deb tor+http://sgvtcaew4bxjd7ln.onion/debian-security stretch/updates main
deb-src tor+http://sgvtcaew4bxjd7ln.onion/debian-security stretch/updates main

deb tor+http://vwakviie2ienjx6t.onion/debian stretch-updates main
deb-src tor+http://vwakviie2ienjx6t.onion/debian stretch-updates main

CD-ROM

If you'd rather use your CD-ROM for installing packages or updating your system automatically with APT, you can put it in your /etc/apt/sources.list. To do so, you can use the apt-cdrom program like this:

# apt-cdrom add

with the Debian CD-ROM in the drive.

You can use -d for the directory of the CD-ROM mount point or add a non-CD mount point (i.e. a USB keydrive).

Name Resolution

On occasion name resolution can break. For example, below is from a S/390x Port running in a QEMU Chroot:

# apt-get update
0% [Working]Unsupported socketcall: 20
Unsupported socketcall: 20
Unsupported socketcall: 20
Unsupported socketcall: 20
Unsupported socketcall: 20
Unsupported socketcall: 20
Unsupported socketcall: 20
Unsupported socketcall: 20
Err:1 http://ftp.us.debian.org/debian testing InRelease
  Temporary failure resolving 'ftp.us.debian.org'
Reading package lists... Done
W: Failed to fetch http://ftp.us.debian.org/debian/dists/testing/InRelease  Temporary failure resolving 'ftp.us.debian.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.

You can temporarily work around it by obtaining the IP address from another machine, and then using the IP address rather than the URI:

echo "deb http://128.30.2.26/debian testing main" > /etc/apt/sources.list

apt-get update
Get:1 http://128.30.2.26/debian testing InRelease [232 kB]
Get:2 http://128.30.2.26/debian testing/main s390x Packages [7583 kB]
Get:3 http://128.30.2.26/debian testing/main Translation-en [5134 kB]    
Fetched 13.0 MB in 32s (403 kB/s)                                              
Reading package lists... Done

Debug Symbol Packages

To debug a crash you often need the related debug symbol files. For most Debian packages these are in dbgsym packages. These are available from a separate archive.

Here is an example entry for your sources.list for Debian 10/Buster dbgsym packages:

deb http://deb.debian.org/debian-debug/ buster-debug main

The same if you running testing.

deb http://deb.debian.org/debian-debug/ testing-debug main

And one more example if you are using the unstable distribution.

deb http://deb.debian.org/debian-debug/ unstable-debug main

More information


CategoryPackageManagement