Before creating additional periodic or timed jobs on unix systems one should check also a maybe untouched setup to avoid collosions especially when running for example backups.
Classical candidates often are for example fstrim jobs or automatic system updates combined with write intensive operations such as backups or logrotate.
Historically there are different systems that may run since January 1rst 1970 and also in parallel since about 10 years.:
- at and cron
- systemd timers
After running the checks you should have an overall overview about what is running where and when regularly before applying new jobs that may collide and lead to unexpected errors.
at
ls /var/spool/crontabs/atjobs/*
Cron
cat /etc/crontab
ls /etc/cron.monthly/*
ls /etc/cron.weekly/*
ls /etc/cron.daily/*
ls /etc/cron.hourly/*
ls /etc/cron.d/*
cat /var/spool/cron/crontabs/*
systemd
systemctl list-timers –all
systemclt –user list-timers –all
A very handy and experienced view on the cron system can be found here: https://myunix.org/linux/linux-cron-job-tutorial/ also with advice when to use newer approaches since 1970 with suggested migrations into AI age.
Systemd’s timer logic is explained at the systemd.io website.