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Adjusting the Time-To-Live (TTL) in DynamicDNS (os-ddclient) Configuration in OPNsense

·233 words·2 mins
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Unfortunately, in OPNsense, it is not possible to set the TTL (Time to Live) for Dynamic DNS, which means DNS entries always have a TTL of 10800 seconds or 3 hours. This limitation undermines the purpose of Dynamic DNS, in my opinion.

To address this, I present a short script that sets the TTL to 300 seconds at system startup. The script adds the line ttl=300 \ after each line that begins with password=. We create the script using Syshook with the “Early” start option, as described in the OPNsense Documentation Autorun.

Script #

We create the script using Syshook with the “Early” start option as described in the OpnSense Documentation Autorun.

The subdirectory after rc.syshook.d indicates when the script will be executed.

  • early: means that a script is started before the system network start.

Instructions #

  1. DDClient Backup:
cp /usr/local/etc/ddclient.conf /usr/local/etc/ddclient.conf.bak
  1. Create Script File:
vi /usr/local/etc/rc.syshook.d/early/50-add_ttl.sh
  1. Insert Script Content:
#!/bin/sh

# Define the file path
DDCLIENT_CONF="/usr/local/etc/ddclient.conf"

# Use sed to insert 'ttl=300 \' followed by a newline after any line starting with 'password='
sed -i '' '/^password=/a\
ttl=300 \\\
' "$DDCLIENT_CONF"
  1. Make Script Executable:
chmod +x /usr/local/etc/rc.syshook.d/early/50-add_ttl.sh
  1. Test Script:

Manually execute the script to ensure it works:

/usr/local/etc/rc.syshook.d/early/50-add_ttl.sh
  1. Verify DDClient Config:

Check if the line ttl=300 \ has been correctly added.

vi /usr/local/etc/ddclient.conf

This is a very basic script, and I would love to hear your suggestions for improvements in the comments! 😊