Linux server administration/Scheduling

Overview
Cron is driven by a crontab (cron table) file, a configuration file that specifies shell commands to run periodically on a given schedule. The crontab files are stored where the lists of jobs and other instructions to the cron daemon are kept. Users can have their own individual crontab files and often there is a system-wide crontab file (usually in  or a subdirectory of  ) that only system administrators can edit.

Each line of a crontab file represents a job, and looks like this: The syntax of each line expects a cron expression made of five fields, followed by a shell command to execute.
 * 1) ┌───────────── minute (0 - 59)
 * 2) │ ┌───────────── hour (0 - 23)
 * 3) │ │ ┌───────────── day of the month (1 - 31)
 * 4) │ │ │ ┌───────────── month (1 - 12)
 * 5) │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday;
 * 6) │ │ │ │ │                                   7 is also Sunday on some systems)
 * 7) * * * * * command to execute
 * 1) * * * * * command to execute
 * 1) * * * * * command to execute

Logging
Cron execution logs can be saved to specific file using rsyslog service.
 * In Ubuntu uncomment in  the line:
 * and restart rsyslog service:
 * and restart rsyslog service:


 * In Debian uncomment in  the line: