The package resource list is used to locate archives of the package distribution system in use on the system. At this time, this manual page documents only the packaging system used by the Debian GNU/Linux system. This control file is located in /etc/apt/sources.list
The source list is designed to support any number of active sources and a variety of source media. The file lists one source per line, with the most preferred source listed first. The format of each line is: type uri args The first item, type determines the format for args uri is a Universal Resource Identifier (URI), which is a superset of the more specific and well-known Universal Resource Locator, or URL. The rest of the line can be marked as a comment by using a #.
The /etc/apt/sources.list.d directory provides a way to add sources.list entries in separate files. The format is the same as for the regular sources.list file. File names need to end with .list and may only contain letters (a-z and A-Z), digits (0-9), underscore (_), hyphen (-) and period (.) characters. Otherwise they will be silently ignored.
The deb type describes a typical two-level Debian archive, distribution/component. Typically, distribution is generally one of stable unstable or testing while component is one of main contrib non-free or non-us The deb-src type describes a debian distribution's source code in the same form as the deb type. A deb-src line is required to fetch source indexes.
The format for a sources.list entry using the deb and deb-src types are:
deb uri distribution [component1] [component2] [...]
The URI for the deb type must specify the base of the Debian distribution, from which APT will find the information it needs. distribution can specify an exact path, in which case the components must be omitted and distribution must end with a slash (/). This is useful for when only a particular sub-section of the archive denoted by the URI is of interest. If distribution does not specify an exact path, at least one component must be present.
distribution may also contain a variable, $(ARCH) which expands to the Debian architecture (i386, m68k, powerpc, ...) used on the system. This permits architecture-independent sources.list files to be used. In general this is only of interest when specifying an exact path, APT will automatically generate a URI with the current architecture otherwise.
Since only one distribution can be specified per line it may be necessary to have multiple lines for the same URI, if a subset of all available distributions or components at that location is desired. APT will sort the URI list after it has generated a complete set internally, and will collapse multiple references to the same Internet host, for instance, into a single connection, so that it does not inefficiently establish an FTP connection, close it, do something else, and then re-establish a connection to that same host. This feature is useful for accessing busy FTP sites with limits on the number of simultaneous anonymous users. APT also parallelizes connections to different hosts to more effectively deal with sites with low bandwidth.
It is important to list sources in order of preference, with the most preferred source listed first. Typically this will result in sorting by speed from fastest to slowest (CD-ROM followed by hosts on a local network, followed by distant Internet hosts, for example).
deb http://http.us.debian.org/debian stable main contrib non-free deb http://http.us.debian.org/debian dists/stable-updates/
The currently recognized URI types are cdrom, file, http, ftp, copy, ssh, rsh.
Uses the archive stored locally (or NFS mounted) at /home/jason/debian for stable/main, stable/contrib, and stable/non-free.
deb file:/home/jason/debian stable main contrib non-free
As above, except this uses the unstable (development) distribution.
deb file:/home/jason/debian unstable main contrib non-free
Source line for the above
deb-src file:/home/jason/debian unstable main contrib non-free
Uses HTTP to access the archive at archive.debian.org, and uses only the hamm/main area.
deb http://archive.debian.org/debian-archive hamm main
Uses FTP to access the archive at ftp.debian.org, under the debian directory, and uses only the stable/contrib area.
deb ftp://ftp.debian.org/debian stable contrib
Uses FTP to access the archive at ftp.debian.org, under the debian directory, and uses only the unstable/contrib area. If this line appears as well as the one in the previous example in sources.list. a single FTP session will be used for both resource lines.
deb ftp://ftp.debian.org/debian unstable contrib
Uses HTTP to access the archive at nonus.debian.org, under the debian-non-US directory.
deb http://nonus.debian.org/debian-non-US stable/non-US main contrib non-free
Uses HTTP to access the archive at nonus.debian.org, under the debian-non-US directory, and uses only files found under unstable/binary-i386 on i386 machines, unstable/binary-m68k on m68k, and so forth for other supported architectures. [Note this example only illustrates how to use the substitution variable; non-us is no longer structured like this]
deb http://ftp.de.debian.org/debian-non-US unstable/binary-$(ARCH)/
m[blue]APT bug pagem. If you wish to report a bug in APT, please see /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command.