Concept of Batch, Cron

Batch

• Batch means:
  • a group of things or people that are dealt with at the same time
  • A group (processed in batches), that is, a group in which something is processed
• Registering a batch is a program created to process various tasks at once.
  • (Resolved through a batch program rather than directly typing commands for a large number of tasks at a fixed time every day or periodically)
• Executing this batch is done by the scheduler, not the developer.

Scheduler

• What is Scheduler:
  • A program that executes a batch program at a certain period or at a specific time;
  • Linux has Crontab as a representative.

Cron

• What is Cron?:
  • The cron command is used when you want to automatically perform a task at a specific time or at a specific time.
  • cron is a scheduling function that allows you to perform a specific task at a specific time.
  • It is not a concept unique to Linux, but a concept in many OSs.
  • The cron system has cron settings that are used by default in the system, and this is called system cron.
  • In addition, there is a user cron that root or general users use by directly setting their cron settings.
• What is crontab:
  • The file that configures cron jobs is called crontab file.
  • The cron process reads the settings in the /etc/crontab file and performs tasks.
  • The crontab file is saved in a different location for each OS.

  • In general, BSD-based Linux is /var/spool/cron/ID

  • On Solaris, it is located in /var/spool/cron/crontabs/ID.
• What is anacron?
  • It is located in /usr/sbin/anacron,
  • A program that works like a cron, and is a tool used to ensure that tasks are executed even when the server is stopped for a certain period of time.