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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 distribution component1 component2 component3
deb-src 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.


The 'distribution' can be either the release code name / alias (wheezy, jessie, stretch, 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.

For example, if you have a system running Debian 9.0 "stretch" and don't want to upgrade when Debian buster releases, use 'stretch' instead of 'stable' for the distribution. If you always want to help test the testing release, use 'testing'. If you are tracking buster and want to stay with it from testing to end of life, use 'buster'.


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 8/Jessie.

deb jessie main
deb-src jessie main

deb jessie-updates main
deb-src jessie-updates main

deb jessie/updates main
deb-src jessie/updates main

If you also want the contrib and non-free components, add contrib non-free after main:

deb jessie main contrib non-free
deb-src jessie main contrib non-free

deb jessie-updates main contrib non-free
deb-src jessie-updates main contrib non-free

deb jessie/updates main contrib non-free
deb-src jessie/updates main contrib non-free

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


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 testing InRelease
  Temporary failure resolving ''
Reading package lists... Done
W: Failed to fetch  Temporary failure resolving ''
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 testing main contrib" > /etc/apt/sources.list

apt-get update
Get:1 testing InRelease [232 kB]
Get:2 testing/main s390x Packages [7583 kB]
Get:3 testing/main Translation-en [5134 kB]
Get:4 testing/contrib s390x Packages [42.7 kB]       
Get:5 testing/contrib Translation-en [44.7 kB]       
Fetched 13.0 MB in 32s (403 kB/s)                                              
Reading package lists... Done

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