Edit the current user's crontab interactively: crontab -e — this opens the editor defined by $EDITOR or $VISUAL.
Add a line using the five-field time syntax: 30 2 * * 1 /usr/local/bin/backup.sh (runs at 02:30 every Monday).
Use special strings for common schedules: @daily, @weekly, @monthly, @reboot — these replace the five-field prefix.
System-wide cron jobs go in /etc/cron.d/ as files with a user field added after the time fields: 30 2 * * * root /usr/local/bin/sysbackup.sh
List the current user's crontab: crontab -l; remove it entirely: crontab -r
Known gotchas
Cron runs jobs in a minimal environment; $PATH is typically shorter than in an interactive shell, so use full absolute paths to all executables and files.
Cron does not run jobs for a user whose account is locked or whose shell is set to /sbin/nologin or /bin/false.
Output from cron jobs is mailed to the user by default if MAILTO is not set; add MAILTO="" at the top of the crontab to suppress mail, or redirect stdout/stderr to a log file in each job line.
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp