Package resource list (sources.list) file Overview for Debian Users
sources.list file is Package resource list for APT.The package resource list is used to locate archives of the package distribution system in use on the system. .
APT is a package tool program which is support the system administrator with the installation and administration of the programs.First one need to know is itís configuration file is located in /etc/apt/sources.list.APT supports a large nuber of different sources of installation.Most used sources are cdrom,file.http,ftp each of these sources are discribed in an individual file and this file is also consider the sequence of these entries from starting to ending of the file.
The format for a sources.list entry using the deb and deb-src types are
deb uri distribution [component1] [componenent2] [Ö]
The first column of the above is kind of source possible values are deb for debian packages for binary format or deb-src for source packages.
The URI for the deb type must specify the base of the Debian distribu-tion, from which APT will find the information it needs.
Distribution may also contain a variable, $(ARCH), which expands to the Debian architecture (i386, m68k, powerpc, Ö) used on the system.
The currently recognized URI types are cdrom, file, http, and ftp.
file - The file scheme allows an arbitrary directory in the file system to be considered an archive. This is useful for NFS mounts and local mirrors or archives.
cdrom - The cdrom scheme allows APT to use a local CDROM drive with media swapping. Use the apt-cdrom program to create cdrom entries in the source list.
http - The http scheme specifies an HTTP server for the archive. If an environment variable http_proxy is set with the format http://server:port/, the proxy server specified in http_proxy will be used. Users of authenticated HTTP/1.1 proxies may use a string of the format http://user:pass@server:port/ Note that this is an insecure method of authentication.
ftp - The ftp scheme specifies an FTP server for the archive. APTís FTP behavior is highly configurable; Please note that a ftp proxy can be specified by using the ftp_proxy environment variable. It is possible to specify a http proxy (http proxy servers often understand ftp urls) using this method and ONLY this method. ftp proxies using http specified in the configuration file will be ignored.
copy - The copy scheme is identical to the file scheme except that packages are copied into the cache directory instead of used directly at their location. This is useful for people using a zip disk to copy files around with APT.
rsh/ ssh - The rsh/ssh method invokes rsh/ssh
to connect to a remote host as a given user and access the
files. No password authentication is possible, prior
arrangements with RSA keys or rhosts must have been made. Access
deb http://mirror.ox.ac.uk/debian/ stable main
non-free/: This directory contains packages
that fail to qualify as free according to the DFSG
deb http://http.us.debian.org/debian/ stable main contrib non-free
Stable security Updates
deb http://security.debian.org/ stable/updates main
deb http://mirror.ox.ac.uk/debian/ unstable
deb http://http.us.debian.org/debian/ unstable main contrib non-free
deb http://http.us.debian.org/debian/ testing main contrib non-free
Debian Unofficial packages for Sarge/stable Opera, Java, Netscape7
sarge main contrib non-free restricted
Debian experimental Sources
If you want more details about sources.list file check man page of sources.list
The above source lists are just an example in each categories.Some thing is missing from these examples let me know about that i will add to the list.