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Cron Scheduling - Automate Update Checks

Cron Scheduling - Automate Update Checks

Update-Watcher is designed to run on a schedule, checking for available updates and sending notifications automatically. This page covers all scheduling options, from the built-in install-cron command to manual crontab configuration and output logging.

Setting Up a Schedule

Using install-cron

The simplest way to set up a daily schedule is the built-in install-cron command:

Terminal
update-watcher install-cron --time 07:00

This creates a cron entry that runs update-watcher run --quiet every day at 07:00. The --quiet flag suppresses terminal output, which is appropriate for unattended cron execution.

To use the default time of 07:00, the --time flag can be omitted:

Terminal
update-watcher install-cron

For a custom cron expression (e.g., twice daily):

Terminal
update-watcher install-cron --cron-expr "0 7,19 * * *"

See install-cron for full command documentation.

Manual Crontab Setup

For more control, edit the crontab directly.

Current User

Terminal
crontab -e

Dedicated Service User

On Linux servers with a dedicated update-watcher user:

Terminal
sudo crontab -u update-watcher -e

Dedicated Service User Entry

When running as a dedicated system user on Linux, include the --as-service-user flag:

Crontab
0 7 * * * /usr/local/bin/update-watcher run --quiet --as-service-user

Schedule Examples

💡
All examples use the full path to the binary (/usr/local/bin/update-watcher). This is important because cron runs with a minimal PATH.

Daily at 07:00 (the most common setup):

Crontab
0 7 * * * /usr/local/bin/update-watcher run --quiet

Twice daily at 07:00 and 19:00:

Crontab
0 7,19 * * * /usr/local/bin/update-watcher run --quiet

Every Monday at 06:00 (weekly):

Crontab
0 6 * * 1 /usr/local/bin/update-watcher run --quiet

Every 6 hours:

Crontab
0 */6 * * * /usr/local/bin/update-watcher run --quiet

Weekdays only at 08:00:

Crontab
0 8 * * 1-5 /usr/local/bin/update-watcher run --quiet

Logging Cron Output

Cron jobs run silently by default. To capture output for debugging and auditing, you have several options.

Redirect to a Log File

Append stdout and stderr to a log file directly in the crontab entry:

Crontab
0 7 * * * /usr/local/bin/update-watcher run --quiet 2>&1 >> /var/log/update-watcher-cron.log

Use the Built-in Log File

Configure a log file in your config.yaml:

config.yaml
settings:
  log_file: "/var/log/update-watcher.log"

With this setting, Update-Watcher writes structured log output to the specified file on every run, regardless of cron redirection.

Cron Mail

By default, cron emails any output to the crontab owner. If your server has a local mail transport agent (MTA) configured, you can rely on this for notifications about cron failures. However, the --quiet flag suppresses most output. Remove --quiet if you want cron mail to include the full report:

Crontab
0 7 * * * /usr/local/bin/update-watcher run 2>&1

Verifying Cron Is Running

Check the Crontab

View the active cron entries:

Terminal
crontab -l

For the dedicated service user:

Terminal
sudo crontab -u update-watcher -l

Check Cron Logs

On systems with syslog, cron execution is logged:

Terminal
grep update-watcher /var/log/syslog

On systemd-based systems:

Terminal
journalctl -u cron --grep update-watcher

Check the Application Log

If a log file is configured, check the last entry:

Terminal
tail -20 /var/log/update-watcher.log

Verify Manually

Run the exact command that cron executes to verify it works:

Terminal
# As your user
/usr/local/bin/update-watcher run --quiet

# As the dedicated service user
sudo -u update-watcher /usr/local/bin/update-watcher run --quiet --as-service-user

Automated Self-Updates

In addition to scheduling update checks, you can schedule automatic self-updates of the Update-Watcher binary. This ensures your monitoring tool stays current with the latest features and fixes.

Terminal
update-watcher install-cron --type self-update --cron-expr "0 3 * * 0"

This runs update-watcher self-update every Sunday at 3:00 AM. Both job types are managed independently – you can install, update, or remove them separately.

A typical production setup with both jobs:

Crontab
# update-watcher scheduled check
0 7 * * * /usr/local/bin/update-watcher run --quiet 2>&1 | logger -t update-watcher
# update-watcher self-update
0 3 * * 0 /usr/local/bin/update-watcher self-update 2>&1 | logger -t update-watcher

See install-cron for all --type options and flags.

Removing Cron Jobs

Using uninstall-cron

Remove the check job:

Terminal
update-watcher uninstall-cron

Remove the self-update job:

Terminal
update-watcher uninstall-cron --type self-update

Remove all Update-Watcher cron jobs:

Terminal
update-watcher uninstall-cron --all

For the dedicated service user:

Terminal
sudo -u update-watcher update-watcher uninstall-cron --all

Manually

Edit the crontab and remove the Update-Watcher lines:

Terminal
crontab -e

Or for the service user:

Terminal
sudo crontab -u update-watcher -e

Troubleshooting

Troubleshooting: Cron Job Not Running

Common causes:

PATH issues – Cron runs with a minimal PATH. Always use the full path to the binary (/usr/local/bin/update-watcher) in crontab entries.
  • Permission denied – The user’s crontab may not have permission to execute the binary or read the config file.
  • Cron daemon not running – Check with systemctl status cron or systemctl status crond.
Troubleshooting: Notifications Not Arriving

Run the command manually with --verbose to diagnose:

Terminal
sudo -u update-watcher update-watcher run --verbose

Check that the send_policy is not set to only-on-updates when there are no updates to report. Use --notify=true to force a notification for testing:

Terminal
sudo -u update-watcher update-watcher run --notify=true

Related

macOS Setup - Update-Watcher on macOS