=====Schedule Recurring System Jobs=====

uses the /etc/crontab file 

if the system is not available anacron checks to see that was missed and will run it.

you also have the /etc/cron.daily /etc/cron/weekly and /etc/cron/monthly

you can place executable files on those directories and they will be executed. You do not have control of the exact time when its done

====Manage Temporary Files====

At system boot, one of the first systemd service units to launch is the systemd-tmpfiles-setup service. This service runs the systemd-tmpfiles command --create --remove option, which reads instructions from the /usr/lib/tmpfiles.d/*.conf, /run/tmpfiles.d/*.conf, and /etc/tmpfiles.d/*.conf configuration files. These configuration files list files and directories that the systemd-tmpfiles-setup service is instructed to create, delete, or secure with permissions.

To prevent long-running systems from filling up their disks with stale data, a systemd timer unit called systemd-tmpfiles-clean.timer triggers at a regular interval the systemd-tmpfiles-clean.service unit, which executes the systemd-tmpfiles --clean command.