only for https://dynv6.com.
change directory or you can custom $PWD :
sudo cd ~/
clone this repository :
git clone miqballharbow/dynv6-updater
execute "crontab" :
crontab -e
copy this text and paste it at the bottom of the crontab :
*/1 * * * * ~/dynv6-updater/update.sh @your-domain @your-token 2>&1