.\" approx: proxy server for Debian archive files
.\" Copyright (C) 2011  Eric C. Cooper <ecc@cmu.edu>
.\" Released under the GNU General Public License
.\" -*- nroff -*-
.TH APPROX 8 "May 2011"
.\" Please adjust this date whenever revising the manpage.

.SH NAME
approx \- proxy server for Debian archive files

.SH SYNOPSIS
.PP
.B approx
[\fIOPTION\fP]...

.SH DESCRIPTION
.B approx
responds to HTTP requests made by
.BR apt\-get (8).
It maintains a cache of Debian archive files that have been previously
downloaded, so that it can respond with a local copy when possible.
If a file not in the cache is requested,
.B approx
will download it from a remote Debian repository and deliver the
contents to the client, simultaneously caching it for future use.

Over time, the
.B approx
server cache will grow to contain multiple, unneeded versions of
Debian packages.  The
.BR approx-gc (8)
program removes these from the cache.

.SH OPTIONS
.TP
.BR \-c " file, " \-\^\-config " file"
Specify an additional configuration file.
May be used multiple times.

.SH USAGE
.PP
.B approx
is invoked by
.BR inetd (8).

.SH EXAMPLES
.PP
Suppose that a client machine's
.I /etc/apt/sources.list
file contains the following lines:
.IP
deb     http://apt:9999/debian    testing main
.br
deb     http://apt:9999/security  testing/updates main
.br
deb-src http://apt:9999/debian    unstable main
.PP
In this example,
.I apt
is the hostname of the
.B approx
server machine on the local network.
Each distribution, such as "debian" or "security", is mapped
to a remote repository in the
.B approx
server's configuration file.
.PP
For example, the
.I approx.conf
file on the
.B approx
server might contain the lines
.IP
debian   http://ftp.debian.org/debian
.br
security http://security.debian.org
.PP
The mapping scheme is very simple.
If the
.I approx.conf
file contains the line
.IP
repository	http://remote-host/initial/path
.PP
then any request to the
.B approx
server of the form
.IP
http://approx-server/repository/rest/of/URL
.PP
is rewritten to
.IP
http://remote-host/initial/path/rest/of/URL
.PP
when there is a "cache miss", and that file is cached as
.IP
/var/cache/approx/repository/rest/of/URL
.PP
(Note that the repository name on the left-hand side is not
included in the rewritten URL unless it is explicitly mentioned
in the right-hand side's initial path.)

.SH FILES
.TP
.I /etc/approx/approx.conf
.br
Configuration file for
.B approx
and related programs.
.TP
.I /var/cache/approx
.br
Default cache directory for archive files.

.SH SEE ALSO
.IR approx.conf (5),
.BR inetd (8),
.BR approx-import (8),
.BR approx-gc (8),
.BR apt-get (8),
.IR sources.list (5)

.SH AUTHOR
Eric Cooper <ecc@cmu.edu>