I need to a crontab execute each 12 hours, so I have the following: 0 */12 * * * . /X.shthen Linux is installing new crontab. after that, I am waiting for 2 hours and still the cron job didn't start?!When has it to start the job?
when the cron job start after installing new crontab?
linux;shell;cron
The crontab entry you've written is equivalent to0 0-23/12 * * * . /X.shThis requests execution on the hour between midnight and 11pm, using 12-hour steps  so cron will run the job every day at midnight and noon.