12.5. Automating Synchronization

Manually synchronizing the Red Hat Satellite repository with the Red Hat Content Delivery Network (CDN) is a time-intensive task. United States business hours tend to be the peak usage time for the Red Hat CDN, so synchronization during that time can be slow. Red Hat encourages customers to automate synchronization at other times to better balance load and ensure quick synchronization. Continental United States business hours are roughly 8:00 AM to 9:00 PM EST (UTC -5), due to four time zones, Monday through Friday. These hours vary seasonally by one hour. Red Hat strongly recommends synchronization during a particular time range. This ensures better synchronization performance.

Set this automation with the addition of a simple cron job. Edit the crontab as root:

crontab -e

This opens the crontab in your default text editor.

Once opened, use the first five fields (minute, hour, day, month, and weekday) to schedule the synchronization. Use 24-hour clock format. Edit the crontab to include random synchronization, like so:

0 1 * * * perl -le 'sleep rand 9000' && cdn-sync --email >/dev/null \
2>/dev/null

This cronjob will run randomly between 1:00 a.m. and 3:30 a.m. system time each night and redirect stdout and stderr from cron to prevent duplicating the more easily read messages from cdn-sync. Use other options from Section 8.1, “Red Hat Satellite CDN Synchronization Tool” if necessary.

After saving the file and exiting the editor, the system installs the modified crontab immediately.