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CloudflareDDNS

Update your CloudFlare DNS records with your current (dynamic) IP address via systemd timers and a bash script.

NOTE: You can rename cfddns.sh anything you want, the script will auto-update itself. However, you MUST update the systemd service file, cfddns.service, ExecStart line manually as explained below

cfddns.sh

Installation:

I recommend putting this in your /usr/local/bin directory or somewhere else in your path so it's easy to run.

  1. Copy the script file to your desired path (/usr/local/bin recommended) and rename as desired. 
    sudo cp cfddns.sh /usr/local/bin/
  2. Make it executable: 
    sudo chmod +x /usr/local/bin/cfddns.sh

Usage:

If you run the script with no parameters, it will display the help screen. The script accepts several parameters with 2 being required. The parameters are summarized here (taken from the help screen). You can access the help screen and example usage screens by running: cfddns.sh -h for help and cfddns.sh -x for examples.

-f: account details file with path This parameter is required. This is the full path to a plain-text file containing your CloudFlare account details. This file must contain 3 lines in the following order:

  • authorized email address This is an email address that is permitted to login to your CloudFlare account.
  • global api-key You can get your Global API-key by going to your CloudFlare dashboard, clicking on your profile picture in the upper-right and opening your profile. Scroll to the very bottom to the API Keys section. Click on the View button next to Global API Key.
  • zone identifier You should be able to find this on the Overview page of your CloudFlare dashboard.

Your completed file should look like:

johndoe@example.com e7882db52804aca6fab22780e055b97056466 492af8aa69f8c44baf043342c74319fd

You should secure this file by changing the owner of the file to root

chown root:root path/to/filename

and then restricting access to only the root user

chmod 600 path/to/filename

-r: target DNS entry to update At least one entry here is required This is the A or AAAA record you want to update the IP address for in your DNS zone file. If you have multiple A or AAAA records you want to update, simply specifiy multiple -r parameters. Note: You can only specify either A records or AAAA records. You have to update IP4 and IP6 records by running this script multiple times (once for A records, once for AAAA records even if the hostname is the same).

-4 or -6: type of record to update The default option is -4 and it does not need to be specified. This will update A records specified by the -r parameter(s). If you specify -6, then AAAA records will updated as specified by the -r parameter(s).

-i: use the specified IP address The script will auto-detect the IP address of the machine it's being run on by accessing an external service and asking for that service to echo the machine's IP address. If running with -4, then the IP4 will be requested for echo. If running with -6, then the IP6 addresses will be requested for echo. This parameter let's you bypass auto-detection and specify a particular address to be used instead. NOTE: The address you supply is NOT checked for correctness. So ensure you're supplying a valid address of the correct type based on your choice of -4 or -6 parameter!

-l (lower-case L): specify where the log file should be written The script will default to writing it's log file in the same directory as the script is located. It will use it's own name and append a .log extension. So, the default name for the log file is cfddns.log. If you rename the script something.sh then the generated log file name will be something.log. This can be messy if you store the script in /usr/bin/local/ as recommended. Therefore, it's recommended you choose a different location for the logfile (/var/log/cfddns.log is recommended).

-h: display help Displays the help screen, which is an abbreviated version of this section you are currently reading.

-x: display examples This is the best way to learn how this script works. Several examples are provided

cfddns.service

This is the systemd file that must be copied to your /etc/systemd/system directory. If you change the name of the cfddns.sh file, you must update the filename in the ExecStart line as shown below:

...
[Service]
Type=oneshot
ExecStart=/full/path/to/your/renamed.file
...

cfddns.timer

This is the timer file that tells your system how often to call the cfddns.service file which runs the cfddns.sh script. By default, the timer is set for 5 minutes after the system boots up (to allow for other processes to initialize even on slower systems like a RasPi) and then run every 15 minutes thereafter as long as the system is powered on. Remember when settings your timer that CloudFlare limits API calls to 1200 every 5 minutes You can change the timer by modifying the relevant section of the cfddns.timer file:

[Timer]
OnBootSec=5min
OnUnitActiveSec=15min

OnBootSec is how long to wait after the system boots up before executing calling thd cfddns.service. OnUnitActiveSec will then wait the specified time from that first (after boot) call before calling cfddns.service again. Therefore, eveything is relative to your system boot up. I recommend setting OnUnitActiveSec to a low value (like 2 minutes) for testing then setting it to a more reasonable time (like 15 minutes) after everything is working.

The log file

The script logs every major action it takes and provides details on any errors it encounters in the log file (see the above section for details on log file location and name). If errors are encountered, they are colour coded red and an explanation of the error code is provided. While the log file is as terse as I felt reasonable, you may still want to configure any logwatch programs to further filter things for you so you don't have to review this log as part of your daily routine. To make that easier, the following conventions are observed in the log file:

  • Errors always appear as "-- [ERROR] text and error code here --"
  • Errors are followed by an explanation of the specific error code on a new line
  • A clean exit appears as "-- [SUCCESS] some text here --"
  • The script always starts a new set of log entries with "-- Start CloudFlare DDNS script execution --
  • All log file entries start with a time-stamp in [square brackets]

Final thoughts

I'm by no means an expert in BASH scripting and I only program/script as a hobby when I find stuff that irritates me and no other good solutions seem easily available. So, by all means, please comment, provide feedback and suggestions to make this script better! Thanks, I hope this helps someone else out!

Please check out my blog at https://mytechiethoughts.com where I tackle problems like this all the time and find free/cheap solutions to tech problems.