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