derpDNS

The derpest dynamic DNS updater on the derp web.

Description

derpDNS simply updates a DNS record of the type you decide. Its main purpose is to dynamically update a single A record making it point to an IP (or another name if updating a CNAME), using OVH API. Think of it as a clone of a <put_your_dyndns_provider_here> client for OVH customers.

derpDNS is expected to run in a scheduled task. Below you'll find detailed instructions about how to schedule a task on macOS, Linux and ~~Windows~~. They should work even if no user is logged in.

Installation

% go get github.com/5ARMALE/derpDNS

Usage

% derpDNS config_file

Configuration

derpDNS uses a simple json file to define its configuration. Please check this link for details on how to get your keys.

{
	"record": {
		"subDomain": "subdomain",
		"zone": "domain.com",
		"recordType": "A"
	},
	"ovh": {
		"endpoint": "ovh-eu",
		"application_key": "app_key",
		"application_secret": "app_secret",
		"consumer_key": "consumer_key"
	}
}

This example will update subdomain.domain.com A record to match your current IP address. As you can check in the code, if the record doesn't exist derpDNS will create it.

macOS

In macOS you should use launchd in order to set up the scheduled task. In order to do so, grab your $EDITOR and define a LaunchDaemon with the following XML file. Then save/copy it to /Library/LaunchDaemons/com.b0nk.derpDNS.plist. You can use the one included in this repo as template. Please note that you may need root to create/copy the file to /Library/LaunchDaemons/.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
	<dict>
		<key>Label</key>
		<string>com.b0nk.derpDNS</string>
		<key>UserName</key>
		<string>your_username</string>
		<key>ProgramArguments</key>
			<array>
				<string>/path/to/derpDNS/binary</string>
				<string>/path/to/derpDNS/config</string>
			</array>
			<key>RunAtLoad</key>
			<true/>
			<key>StartInterval</key>
			<integer>3600</integer>
			<key>StandardErrorPath</key>
			<string>/tmp/derpDNS.log</string>
        </dict>
</plist>

All right, let's explain what we did here:

We set the label (name) for this LaunchDaemon to com.b0nk.derpDNS.
The LaunchDaemon will run with my_username permissions.
It will execute /path/to/derpDNS/binary with /path/to/derpDNS/config as argument.
We tell launchd that the program should run right after we load the LaunchDaemon with the key RunAtLoad
The task will run every hour (3600 secs)
As derpDNS spits everything out to STDERR, a key named StandardErrorPath tells launchd where STDERR will be logged for derpDNS. In this case, you will have a log containing every bit of output on /tmp/derpDNS.log

Now, once our LaunchDaemon is set up, we should tell launchd to launch it:

% sudo launchctl load /Library/LaunchDaemons/com.b0nk.derpDNS.plist

No news are always good news, so Console.App shouldn't spit anything if everything went fine. Now you can go and check /tmp/derpDNS.log to see if it did something.

Linux

It's simpler in Linux. You only have to edit /etc/crontab and add the following line:

0 * * * * your_username cd /path/to/derpDNS/binary && /path/to/derpDNS/binary /path/to/derpDNS/config | logger -t derpDNS

It should work right away and run derpDNS every hour and log to syslog.

TODO

Find out an easy way to set up a system scheduled task on Windows.
Anything you might find.

GeoffreyFrogeye/derpDNS