Swap memory in linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and RAM is full, then inactive pages in memory are moved to swap space. swap spaces are located on hard drives.
The main function of yum is that it allows automatic updates, package and dependency management on RPM – based distributions. It works with software repositories, which can be accessed locally or over a network.
Crontab is a system daemon used to execute desired tasks at designated times. If the system is shutdown , when the job is scheduled , it is not executed . crontab is used to maintain crontab files for individual users . Each users can have their own crontab .