Category: Linux

Namecheap DDNS Updates via DD-WRT

DD-WRT has limit support for different DDNS update mechanisms.
A simple workaround is the following script.

Login to your router and go to Administration > Commands

Add the following to the startup script, modifying it for your details

Finally, go to the Administration > Management and add a crontab to update it hourly.

Enjoy 😉

DD-WRT with CA Signed certificate, bundle and key

Surprisingly enough, finding new documentation on DD-WRT, with a custom certificate, is difficult.
Yes, there is information around, however it’s date years old which doesn’t inspire a lot of confidence.

Login to your DD-WRT front end.
Go to Management -> commands.

In the commands box, paste your keys like so.
Finally at the bottom choose ‘save startup’ and your are done.
If you are concerned about it going wrong, you can run it interactively on the console first to test 🙂


Golang DD-WRT Bandwidth Usage with Conky

I setup a golang script to fetch the DD-WRT bandwidth usage for the previous 2 months, as well as the last 30 days(rolling).
Using conky then i can display it on my desktop.
My ISP (digiweb), don’t provide any means to check your bandwidth.
Picture at end of post 🙂

Golang DD-WRT script

Conky script Integration


Debian SID Opendmarc Installation and Configuration

In this post i will capture the installation of opendmarc and how its configure alongside Opendkim.

Install opendmarc

Configure systemd service file

The specific changes here are lines #9 EnvironmentFile #13 -p $SOCKET

Defaults File

Opendmarc Config file

Modify Postfix milters
If you are running both opendkim and opendmarc your milters will look like this:

Restart the service


Now go modify your DNS, adding a TXT record ‘_dmarc‘with the value ‘v=DMARC1; p=none;

When you have validated dmarc is working properly you can change p=none to p=reject

How can you validate it?

There are a number of tools online to help you with this, also you open up a mail in google and click ‘show original’.



Other resources


Debian SID Opendkim Installation and Configuration Woes

TL;DR Opendkim. Hats off the to folk who do marvelous packing 99.99999% percent of the time.

But sometimes they just get it wrong or at least all documentation regarding the package, does not match up with the behavior the packager intended.
That said, hopefully i will help solve some of these issues here.

I assume you have postfix already working and you are just looking to add dkim support.

Install opendkim

Configure systemd service file

The specific changes here are lines #9 EnvironmentFile #13 -p $SOCKET

Defaults File

Opendkim Config file

Specific changes here are lines #7 hashed out socket file,  it simply does not work.
The only way to get opendkim to honour this setting is passing it to the command line #13 of the service file.

Modify /etc/postfix/ and add/edit the following lines

Create referenced folders for your open dkim keys




Create private/public key for signing

Your directory should now look like this

Opendkim Treeview of files

Tell systemd to reload the the daemon files and restart


Now go modify your DNS, adding a TXT record ‘default._domainkey‘.
Copy and paste everything between the parenthesis. ( everything here ) into the value field of the TXT record


Other resources