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+# openresolv
+
+openresolv is a [resolvconf](https://en.wikipedia.org/wiki/Resolvconf)
+implementation which manages `/etc/resolv.conf`.
+
+`/etc/resolv.conf` is a file that holds the configuration for the local
+resolution of domain names.
+Normally this file is either static or maintained by a local daemon,
+normally a DHCP daemon. But what happens if more than one thing wants to
+control the file?
+Say you have wired and wireless interfaces to different subnets and run a VPN
+or two on top of that, how do you say which one controls the file?
+It's also not as easy as just adding and removing the nameservers each client
+knows about as different clients could add the same nameservers.
+
+Enter resolvconf, the middleman between the network configuration services and
+`/etc/resolv.conf`.
+resolvconf itself is just a script that stores, removes and lists a full
+`resolv.conf` generated for the interface. It then calls all the helper scripts
+it knows about so it can configure the real `/etc/resolv.conf` and optionally
+any local nameservers other than libc.
+
+## Reasons for using openresolv
+
+Why openresolv over the
+[Debian implementation](http://qref.sourceforge.net/Debian/reference/ch-gateway.en.html#s-dns-resolvconf)?
+Here's some reasons:
+ * Works with
+ [POSIX shell and userland](http://www.opengroup.org/onlinepubs/009695399)
+ * Does not need awk, grep or sed which means we can work without `/usr`
+ mounted
+ * Works with other init systems than Debians' out of the box
+ * Available as a 2 clause
+ [BSD license](http://www.freebsd.org/copyright/freebsd-license.html)
+ * Prefer configs via IF_METRIC for dynamic ordering
+ * Configures zones for local resolvers other than libc
+
+The last point is quite important, especially when running VPN systems.
+Take the following resolv.conf files which have been generated by a
+[DHCP client](../dhcpcd) and sent to resolvconf:
+
+```
+# resolv.conf from bge0
+search foo.com
+nameserver 1.2.3.4
+
+# resolv.conf from tap0
+domain bar.org
+nameserver 5.6.7.8
+```
+
+In this instance, queries for foo.com will go to 1.2.3.4 and queries for
+bar.org will go to 5.6.7.8.
+This does require the resolvers to be configured to pickup the resolvconf
+generated configuration for them though.
+openresolv ships with helpers for:
+ * [unbound](http://www.unbound.net/)
+ * [dnsmasq](http://www.thekelleys.org.uk/dnsmasq/doc.html)
+ * [ISC BIND](http://www.isc.org/software/bind)
+ * [PowerDNS Recursor](http://wiki.powerdns.com/trac)
+
+See the
+[configuration section](https://roy.marples.name/projects/openresolv/config)
+for more details.