Cron is used on Linux to run scheduled tasks. The configuration to be found in:

• / Etc / crontab - system-wide
• / Etc / cron.d
• / Etc / cron.daily - daily call by crontab
• / Etc / cron.hourly - called by crontab hourly
• / Etc / cron - Monthly called by crontab
• / Etc / cron.weekly - weekly call Duch crontab

Furthermore, can be stored per user, a separate crontab. To create a file with a cron job and does this by:

cron dateiname

The format of cron files:

Instruction to be executed *****
┬ ┬ ┬ ┬ ┬
│ │ │ │ │
│ │ │ │ └ ─ ─ ─ ─ week (0-7) (Sunday = 0 or = 7)
│ │ │ └ ─ ─ ─ ─ ─ ─ month (1-12)
│ │ └ ─ ─ ─ ─ ─ ─ ─ ─ day (1-31)
│ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ hour (0-23)
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ minute (0-59)

The wildcard * can also be used.
Furthermore, as divider * / 2 - every 2nd Minute for example.
And areas such as 1-5 for weekdays as well.

In practice there is almost nothing that could withstand its schedule using cron.