cronie — Cron Job Scheduler

cronie is the standard cron daemon — it runs commands on a schedule defined in crontab files. It is pre-installed and active by default on Shani OS.

For most recurring tasks, systemd timers are the recommended alternative: they integrate with journalctl for logging, support calendar expressions and monotonic intervals, and handle missed runs via Persistent=true. Use cron when you need the simplicity of a single-line schedule, compatibility with scripts that assume cron, or per-user jobs without root.

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Crontab Syntax

# ┌── minute (0–59)
# │ ┌── hour (0–23)
# │ │ ┌── day of month (1–31)
# │ │ │ ┌── month (1–12)
# │ │ │ │ ┌── day of week (0–7, 0 and 7 = Sunday)
# │ │ │ │ │
# * * * * *  command to run

Common schedule examples:

| Schedule | Meaning | |----------|---------| | | Every minute | | 0 | Every hour (on the hour) | | 0 3 | Daily at 03:00 | | 0 3 0 | Every Sunday at 03:00 | | 0 3 1 | First of every month at 03:00 | | /15 | Every 15 minutes | | 0 9-17 * 1-5 | Every hour from 9 to 17, Mon–Fri |

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User Crontabs

# Edit your own crontab
crontab -e

# List your crontab
crontab -l

# Remove your crontab entirely
crontab -r

# Edit another user's crontab (root only)
sudo crontab -e -u youruser

# List another user's crontab
sudo crontab -l -u youruser

Example User Crontab

# Send output to a log file instead of local mail
MAILTO=""

# Run a backup script daily at 3 AM
0 3 * * * /home/user/scripts/backup.sh >> /home/user/logs/backup.log 2>&1

# Sync documents to cloud every 30 minutes
*/30 * * * * rclone sync ~/Documents gdrive:Documents --quiet

# Clear temp files every Sunday at midnight
0 0 * * 0 find /tmp -user $USER -mtime +7 -delete

Tip: Redirect both stdout and stderr to a log file with >> /path/to/log 2>&1. Without redirection, cron mails output to the local user — set MAILTO="" to suppress mail silently.

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System Crontabs

System-wide cron jobs are placed directly in /etc/crontab or as files in these directories (no crontab editing required — just drop a script in the right directory):

| Directory | Frequency | |-----------|-----------| | /etc/cron.hourly/ | Every hour | | /etc/cron.daily/ | Once daily | | /etc/cron.weekly/ | Once weekly | | /etc/cron.monthly/ | Once monthly |

Scripts placed in these directories must be executable and must not have a file extension:

sudo cp myscript.sh /etc/cron.daily/myscript
sudo chmod +x /etc/cron.daily/myscript

For custom schedules, add a line to /etc/crontab:

# /etc/crontab — note the extra 'username' field before the command
0 4 * * * root /usr/local/bin/maintenance.sh

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Service Management

# cronie is enabled by default — check its status
systemctl status cronie

# Restart if jobs stop running after a config change
sudo systemctl restart cronie

# View cron execution logs
journalctl -u cronie -f

# See recent cron activity (last 50 lines)
journalctl -u cronie -n 50

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Cron vs Systemd Timers

Prefer systemd timers when:

• You need the output captured in journalctl automatically
• The job must run at boot if a scheduled run was missed (Persistent=true)
• The job is already a systemd service
• You want precise control over the environment (working directory, user, resource limits)

Prefer cron when:

• You need a quick per-user scheduled task without root
• The schedule is simple and the one-liner format is sufficient
• You are adapting an existing cron-based script

See the Backup & Recovery page for an example of a systemd user timer running a restic backup.

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Troubleshooting

| Issue | Solution | |-------|----------| | Job not running | Check journalctl -u cronie for errors; verify the script is executable (chmod +x); test the command manually as the cron user | | Job runs but does nothing | Cron has a minimal PATH — use full paths to binaries (e.g., /usr/bin/rsync not rsync), or set PATH= at the top of the crontab | | Output being mailed to root | Add MAILTO="" to suppress, or MAILTO=youruser to redirect; ensure Exim is running if you want mail delivery | | Missed jobs after suspend/hibernate | cron does not catch up missed jobs after sleep — use a systemd timer with Persistent=true instead | | Editing crontab opens wrong editor | Set VISUAL or EDITOR env variable: export EDITOR=nano |