Cron

Every user on a system may have their own crontab file.

cron files are usually located under /var/spool/cron.

The /etc/crontab file is system-wide.

The /etc/cron.d directory may contain cron files. Some Linux distributions have /etc/cron.{hourly,daily,weekly,monthly} directories

cron.deny specifies users who cannot use cron.

cron daemon will not catchup and run past queries in a case of the system being off (powered off or the daemon being stopped).

cron logs the actions via syslog (either /var/log/cron or /var/log/syslog).

crontab

In the crontab file you cannot use \ to extend a command over multiple lines.

cron requires that commands are terminated with a new line, including the last line.