The software utility cron is a time-based job scheduler in Unix-like computer operating systems.
# crontab -e
SHELL=/bin/bash
[email protected]
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
# For details see man 4 crontabs
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week(0-6)(Sunday=0or7)OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed
# backup using the rsbu program to the internal 4TB HDD and then 4TB external
01 01 * * * /usr/local/bin/rsbu -vbd1 ; /usr/local/bin/rsbu -vbd2
# Set the hardware clock to keep it in sync with the more accurate system clock
03 05 * * * /sbin/hwclock --systohc
# Perform monthly updates on the first of the month
# 25 04 1 * * /usr/bin/dnf -y updateEdit the cron time table with:
crontab -erun every minute:
* * * * * /root/your-script.shrun at the first and 31st minute every hour:
1,31 * * * * /root/your-script.shrun at the first minute of 8-10 a.m. every day:
1 8-10 * * * /root/your-script.shrun every 2 days:
* * */2 * * /root/your-script.shrun scripts in /etc/cron.hourly
0 1 * * * root run-parts /etc/cron.hourly