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Ubuntu 18.04: WP-Cron and GridPane’s GP-Cron

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Ubuntu 20.04 and 22.04 Servers

If your server is running our Ubuntu 20.04 or 22.04 stack, please see this article:
Ubuntu 20.04 & 22.04: WP-Cron and GridPane’s GP-Cron

Table of Contents

  1. Introduction
  2. Ubuntu 18.04 and GP-Cron
  3. Enable GP-Cron
  4. Disable GP-Cron
  5. Checking Your Cron Job
  6. How to List All Sites Running GP-Cron

Introduction

WP-Cron is how WordPress handles scheduling time-based tasks such as checking for updates and publishing scheduled post.

At GridPane, we have GP-Cron, which does the same thing, but at the server level. Unlike WP-Cron, which relies on people visiting your website, you can set it to run at specific time intervals, ensuring that things like scheduled posts won’t miss being published.

Activating GP-Cron will disable the native WordPress cron via your websites wp-config.php file.

Ubuntu 18.04 and GP-Cron

GP-Cron is NOT active by default on our Ubuntu 18.04 stack, so it needs to be manually enabled on a per-site basis. 

This stack also runs our original GP-Cron, which is a straightforward cron job to trigger the WP-Cron at an interval of your choosing. 

Enable GP-Cron

The following will set up GP-Cron to run on your website (it is not active by default on Ubuntu 18.04 or 20.04). This command will disable WP-cron is set a server cron job:

gp site {site.url} -gpcron-on {minute.interval}
  • {site.url} is your site.
  • {minute.interval} is an integer value for minutes, it can be set from 1 to 60 minutes.

The cron will run as a system user cron for your site’s PHP user.

For example:

gp site yourwebsite.com -gpcron-on 15

The above example sets GP-Cron to run every 15 minutes.

Disable GP-Cron

To disable GP-Cron you can run the following command (replace {site.url} with your website URL):

gp site {site.url} -gpcron-off

For example:

gp site yourwebsite.com -gpcron-off

Checking Your Cron Job 

These Cron jobs do not run under the root cron, as this would elevate WP PHP processes to root privilege and create a security risk, so you won’t find these in the regular crontab. You will need to check the website’s system user-specific crontab.

To do that you need to first move into your websites system user and display the crontab:

sudo su - {system.user}
crontab -l

{system.user} is the system user your site belongs to.

For example:

sudo su - steveswebs8348

You can also check running just one singular command as follows:

sudo su - {system.user} -c "crontab -l"

If you have run the command correctly, say for 1 minute, you should see the following in your users crontab:

*/1 * * * * wget -q -O - http://{your.site}/wp-cron.php?doing_wp_cron >/dev/null 2>&1

For more information on WP-Cron, you can check out the official documentation here:

https://developer.wordpress.org/plugins/cron/

Return to the root user

Once done checking your cron jobs you return to the root user with CTRL+D.

How to List All Sites Running GP-Cron

To view a list of all sites on a given server using GP-Cron you can run the command below to search each site’s env file for the value cron:true:

grep 'cron:true' /var/www/*/logs/*.env

Here’s an example of what the output will look like:

/var/www/anothergpcrontest.site/logs/anothergpcron.test.site.env:cron:true
/var/www/gpcrontest.site/logs/gpcron.test.site.env:cron:true'