+ As a temporary exception &apt-get; (not &apt;!) raises warnings only if it
+ encounters unauthenticated archives to give a slightly longer grace period
+ on this backward compatibility effecting change. This exception will be removed
+ in future releases and you can opt-out of this grace period by setting the
+ configuration option <option>Binary::apt-get::Acquire::AllowInsecureRepositories</option>
+ to <literal>false</literal> or <option>--no-allow-insecure-repositories</option>
+ on the command line.
+ </para>
+
+ <para>
+ You can force all APT clients to raise only warnings by setting the
+ configuration option <option>Acquire::AllowInsecureRepositories</option> to
+ <literal>true</literal>. Individual repositories can also be allowed to be insecure
+ via the &sources-list; option <literal>allow-insecure=yes</literal>.
+ Note that insecure repositories are strongly discouraged and all options
+ to force apt to continue supporting them will eventually be removed.
+ Users also have the <option>Trusted</option> option available to disable
+ even the warnings, but be sure to understand the implications as detailed in
+ &sources-list;.
+ </para>
+
+ <para>
+ A repository which previously was authentication but would loose this state in
+ an <command>update</command> operation raises an error in all APT clients
+ irrespective of the option to allow or forbid usage of insecure repositories.
+ The error can be overcome by additionally setting
+ <option>Acquire::AllowDowngradeToInsecureRepositories</option>
+ to <literal>true</literal> or for Individual repositories with the &sources-list;
+ option <literal>allow-downgrade-to-insecure=yes</literal>.
+ </para>
+
+ <para>
+ Note: All APT-based package management front-ends like &apt-get;, &aptitude;
+ and &synaptic; support this authentication feature, so this manpage uses
+ <literal>APT</literal> to refer to them all for simplicity only.