cron to run every 30 minutes code example

Example 1: crontab every 30 minutes in specific minute

// every 30 minutes
*/30 * * * *

// it depends on the crontab version you are using
// example: every 30 minutes at number '5'

// mode 1
5,35 * * * *

// mode 2
5/30 * * * *

Example 2: run cron every 15 minutes

*/15 * * * *