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#use wml::debian::template title="Push Mirroring"
<p>Push mirroring is a form of mirroring that minimizes the time it takes
for changes to the archive to reach mirrors. The master server uses
a triggering mechanism to immediately inform the client mirror that it
needs to be updated.</p>
<p>Push mirroring takes more effort to set up since the maintainers
of the upstream and downstream mirror must exchange information. The benefit
is that the upstream mirror initiates the mirror process immediately after
its archive has been updated. This allows changes to the archive to
propagate quickly.
</p>
<h2>Explanation of the method</h2>
<p>Triggers are done using ssh. The push-server sshs into the pushed server's
mirror account using public-key authentication. The key is set up such that
this action may only trigger a mirror run, no other commands. The pushed
server then runs ftpsync to update the archive using rsync as normal.
<br />
Exchanging public keys and potentially access to restricted rsync servers
requires coordination between a mirror operator and their upstream source.
</p>
<h2>Setting up a push client mirror</h2>
<p>To become a push client for the FTP archive, you will need to set up
mirroring using our standard <a href="ftpmirror#how">ftpsync</a> script set.
<br />
Once that is working, add the public sshkey of your upstream mirror
in your <code>~<user>/.ssh/authorized_keys</code> with a
<code>command="~/bin/ftpsync</code>
restriction. (You may have ftpsync in a different directory, adapt
accordingly.)
</p>
<h2>Push-Primary client sites</h2>
<p>Push-Primary client mirrors, also referred to as Tier-1 mirrors, are the
push client mirrors which sync directly from Debian's internal syncproxy
network.
</p>
<p>If your site is <strong>very</strong> well connected (both very good
bandwidth and well connected to major backbones) and you are willing to let
other sites mirror from your site, you may want to let us know so we can
consider you for a push mirror. Please contact the Debian mirrors team for
set-up details. Note however, that we can't accept all requests for becoming a
primary push mirror as we already have a fair number of Tier-1 mirrors.
</p>
<h2>Setting up a push server mirror</h2>
<p>Given the large number of mirrors and the size of the Debian archive, it
is not feasible for all the mirrors to use Debian's internal syncproxies as the
upstream source for Debian. It is much more efficient if the load is
distributed among a number of push mirrors distributed throughout the globe.
</p>
<p>Therefore, a number of Push-Primary sites are, in turn, push servers for
their downstreams. If you want to configure your site as a push server for
your downstream sites, see the <a href="push_server">details on setting up a push server</a>.
</p>
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