vim /usr/bin/cloudflare-ddns.sh
下記のサイトが参考になります。
https://zenn.dev/ten_takano/articles/20230706-cloudflare-ddns
vim /etc/systemd/system/cloudflare-ddns.service
[Unit]
Description=Sync IP Address to cloudflare-ddns
After=network.target
[Service]
ExecStart=/bin/sh /usr/bin/cloudflare-ddns.sh
WorkingDirectory= /usr/bin
vim /etc/systemd/system/cloudflare-ddns.timer
[Unit]
Description=Sync IP address to cloudflare-ddns every day
After=network.target
[Timer]
OnCalendar=*-*-* 4:*:*
[Install]
WantedBy=timers.target