Allow interval to be configurable

README.md

@@ -58,7 +58,7 @@ The architectures supported by this image are:
 
 - Go to the [duckdns website](https://duckdns.org/), register your subdomain(s) and retrieve your token.
 - Create a container with your subdomain(s) and token. If you own `user.duckdns.org`, you set `SUBDOMAINS=user`. You would NOT set a sub subdomain like `overseerr` from `overseerr.user.ducksdns.org`.
-- It will update your IP with the DuckDNS service every 5 minutes (with a random jitter).
+- It will update your IP with the DuckDNS service at a configurable interval (default: every 5 minutes, with a random jitter). Use the `UPDATE_INTERVAL` environment variable to customize the update frequency.
 
 ## Notice regarding automatic detection
 
@@ -94,6 +94,7 @@ services:
       - SUBDOMAINS=subdomain1,subdomain2
       - TOKEN=token
       - UPDATE_IP=ipv4 #optional
+      - UPDATE_INTERVAL=5m #optional
       - LOG_FILE=false #optional
     volumes:
       - /path/to/duckdns/config:/config #optional
@@ -112,6 +113,7 @@ docker run -d \
   -e SUBDOMAINS=subdomain1,subdomain2 \
   -e TOKEN=token \
   -e UPDATE_IP=ipv4 `#optional` \
+  -e UPDATE_INTERVAL=5m `#optional` \
   -e LOG_FILE=false `#optional` \
   -v /path/to/duckdns/config:/config `#optional` \
   --restart unless-stopped \
@@ -131,6 +133,7 @@ Containers are configured using parameters passed at runtime (such as those abov
 | `-e SUBDOMAINS=subdomain1,subdomain2` | multiple subdomains allowed, comma separated, no spaces, if your domain is user.duckdns.org you put user, not a sub-subdomain |
 | `-e TOKEN=token` | DuckDNS token |
 | `-e UPDATE_IP=ipv4` | Set to `ipv6` or `ipv4` to update  **only** your public IPv4/6 address. Set to `both` to update IPv6 and IPv4 address. This variable makes use of a [third-party service](#notice-regarding-automatic-detection). Omitting this variable uses DuckDNS for detection and only supports IPv4. `both` and `ipv6` modes needs [host networking](#networking-net). |
+| `-e UPDATE_INTERVAL=5m` | Set the update interval. Format: `[number][m|h]` where `m` is minutes (5-60) or `h` is hours (1-24). Examples: `5m` (every 5 minutes), `30m` (every 30 minutes), `2h` (every 2 hours). Default is `5m`. |
 | `-e LOG_FILE=false` | Set to `true` to log to file (also need to map /config). |
 | `-v /config` | Persistent config files. Also set `LOG_FILE=true` to keep address history. |
 | `--read-only=true` | Run container with a read-only filesystem. Please [read the docs](https://docs.linuxserver.io/misc/read-only/). |
@@ -299,6 +302,7 @@ Once registered you can define the dockerfile to use with `-f Dockerfile.aarch64
 
 ## Versions
 
+* **18.02.26:** - Add configurable update interval via UPDATE_INTERVAL environment variable.
 * **27.07.25:** - Rebase to Alpine 3.22.
 * **27.01.25:** - Rebase to Alpine 3.21.
 * **24.06.24:** - Rebase to Alpine 3.20.

readme-vars.yml

@@ -25,6 +25,7 @@ param_env_vars:
 opt_param_usage_include_env: true
 opt_param_env_vars:
   - {env_var: "UPDATE_IP", env_value: "ipv4", desc: "Set to `ipv6` or `ipv4` to update  **only** your public IPv4/6 address. Set to `both` to update IPv6 and IPv4 address. This variable makes use of a [third-party service](#notice-regarding-automatic-detection). Omitting this variable uses DuckDNS for detection and only supports IPv4. `both` and `ipv6` modes needs [host networking](#networking-net).", env_options: ["", "ipv4", "ipv6", "both"]}
+  - {env_var: "UPDATE_INTERVAL", env_value: "5m", desc: "Set the update interval. Format: `[number][m|h]` where `m` is minutes (5-60) or `h` is hours (1-24). Examples: `5m` (every 5 minutes), `30m` (every 30 minutes), `2h` (every 2 hours). Default is `5m`.", env_options: ["5m", "30m", "1h", "2h"]}
   - {env_var: "LOG_FILE", env_value: "false", desc: "Set to `true` to log to file (also need to map /config).", env_options: ["false", "true"]}
 opt_param_usage_include_vols: true
 opt_param_volumes:
@@ -36,7 +37,7 @@ app_setup_block_enabled: true
 app_setup_block: |
   - Go to the [duckdns website]({{project_url}}), register your subdomain(s) and retrieve your token.
   - Create a container with your subdomain(s) and token. If you own `user.duckdns.org`, you set `SUBDOMAINS=user`. You would NOT set a sub subdomain like `overseerr` from `overseerr.user.ducksdns.org`.
-  - It will update your IP with the DuckDNS service every 5 minutes (with a random jitter).
+  - It will update your IP with the DuckDNS service at a configurable interval (default: every 5 minutes, with a random jitter). Use the `UPDATE_INTERVAL` environment variable to customize the update frequency.
 
   ## Notice regarding automatic detection
 
@@ -85,6 +86,7 @@ init_diagram: |
   "duckdns:latest" <- Base Images
 # changelog
 changelogs:
+  - {date: "18.02.26:", desc: "Add configurable update interval via UPDATE_INTERVAL environment variable."}
   - {date: "27.07.25:", desc: "Rebase to Alpine 3.22."}
   - {date: "27.01.25:", desc: "Rebase to Alpine 3.21."}
   - {date: "24.06.24:", desc: "Rebase to Alpine 3.20."}

root/app/duck.sh

@@ -7,6 +7,7 @@ if [[ "${LOG_FILE,,}" = "true" ]]; then
     touch /config/logrotate.status
     chmod 640 /config/logrotate.status
     /usr/sbin/logrotate -s /config/logrotate.status /config/logrotate.conf
+    echo "duck.sh invoked at $(date)" >> "${DUCK_LOG}"
 else
     DUCK_LOG="/dev/null"
 fi

root/defaults/abc.tmpl

@@ -0,0 +1,2 @@
+# min   .  hour     day     month   weekday command
+${MINUTES} ${HOURS} *       *       *       sleep $((60 + $RANDOM % 230)); /app/duck.sh 2>&1

root/etc/s6-overlay/s6-rc.d/init-duckdns/run

@@ -1,12 +1,53 @@
 #!/usr/bin/with-contenv bash
 # shellcheck shell=bash
 
-#Check to make sure the subdomain and token are set
+# Check to make sure the subdomain and token are set
 if [ -z "${SUBDOMAINS}" ] || [ -z "${TOKEN}" ]; then
     echo "Please pass both your subdomain(s) and token as environment variables in your docker run command. See the readme for more details."
     sleep infinity
 fi
 
+# Render template into real crontab with default interval if not provided
+UPDATE_INTERVAL=${UPDATE_INTERVAL:-5m}
+if [[ ! "$UPDATE_INTERVAL" =~ ^[0-9]+[mh]?$ ]]; then
+    echo "Invalid interval format: \"$UPDATE_INTERVAL\", expected format \"[0-9]+[mh]?\""
+    exit 1
+fi
+
+case "$UPDATE_INTERVAL" in
+  *h)
+    HOURS=${UPDATE_INTERVAL%h}
+    if (( HOURS < 1 || HOURS > 24 )); then
+        echo "Update interval must be between 1-24 hours"
+        exit 1
+    fi
+    # Cron hour field is 0-23, so 24h must be normalized to daily at midnight.
+    if (( HOURS == 24 )); then
+        HOURS="0"
+    else
+        HOURS="*/$HOURS"
+    fi
+    MINUTES="0"
+    ;;
+  *)
+    MINUTES=${UPDATE_INTERVAL%m}
+    if (( MINUTES < 5 || MINUTES > 60 )); then
+        echo "Update interval must be between 5-60 minutes"
+        exit 1
+    fi
+    HOURS="*"
+    # Cron minute field is 0-59, so 60m must be normalized to top of each hour.
+    if (( MINUTES == 60 )); then
+        MINUTES="0"
+    else
+        MINUTES="*/$MINUTES"
+    fi
+    ;;
+esac
+
+sed "s|\${MINUTES} \${HOURS}|$MINUTES $HOURS|g" < /defaults/abc.tmpl > /etc/crontabs/abc
+chmod 644 /etc/crontabs/abc
+
 if [[ ! -f /config/logrotate.conf ]]; then
     cp /defaults/logrotate.conf /config/logrotate.conf
     chmod 640 /config/logrotate.conf