Yum Cron: Why We Need It and How to Use It

What is Yum Cron?

Yum Cron is a utility for RHEL-based systems (including CentOS, Fedora, and other similar distributions) that automates the task of updating software packages using Yum, the default package manager. Yum Cron runs in the background at regular intervals, checking for and applying available updates to your system. It can be configured to either notify you of available updates or automatically apply them, ensuring that your system remains current and protected against security vulnerabilities.

Why Do We Need Yum Cron?

Keeping software packages updated is a critical aspect of server management. Outdated packages can expose your server to a wide range of security risks and compatibility issues. Regularly applying updates can:

1. Enhance Security: Unpatched vulnerabilities are a major cause of system compromises. Yum Cron helps ensure your system is always patched against the latest security threats.

2. Minimize Downtime: Manually updating software can require frequent intervention, leading to potential service interruptions. Yum Cron automates the process, allowing updates to occur without manual oversight, minimizing downtime.

3. Save Time: System administrators often need to manage multiple servers. Automating routine tasks like updates frees up time for focusing on more complex issues.

4. Compliance: Many industries require systems to be patched promptly as part of compliance measures. Yum Cron helps you maintain these standards effortlessly.

How to Install and Configure Yum Cron

Now that you understand why Yum Cron is useful, let’s go over how to install and configure it to suit your needs.

Step 1: Install Yum Cron

To install Yum Cron, you simply need to run the following command in your terminal:

sudo yum install yum-cron

This command will install the necessary package and dependencies.

Step 2: Enable and Start Yum Cron

Once installed, you need to enable and start the Yum Cron service:

sudo systemctl enable yum-cron
sudo systemctl start yum-cron

This ensures that Yum Cron will automatically run whenever your server starts.

Step 3: Configure Yum Cron

The configuration file for Yum Cron is located at /etc/yum/yum-cron.conf. You can edit it to suit your preferences:

sudo nano /etc/yum/yum-cron.conf

Here are some important settings you can configure:

• Update Notification: You can choose whether you want Yum Cron to only notify you of updates or automatically apply them. The relevant settings are found under the email and update_cmd options.

• Apply Updates Automatically: To automatically apply security updates, set the update_cmd line to:

  update_cmd = security
  

  To apply all updates automatically, set it to:

  update_cmd = default
  

• Email Notifications: You can specify an email address for notifications. This helps keep you informed about updates without needing to manually check logs:

  email_from = root@localhost
  email_to = youremail@example.com
  

Step 4: Verifying Yum Cron’s Operation

Once configured, you can verify if Yum Cron is working correctly by checking its log file located at /var/log/yum.log. This file will give you an overview of the updates that were applied.

You can also use the following command to check the status of Yum Cron:

sudo systemctl status yum-cron

This command will show you if Yum Cron is active and whether it’s applying updates as expected.

Best Practices for Using Yum Cron

1. Backup Regularly: Always ensure that you have recent backups of your system before enabling automatic updates. This will help you recover in case an update causes an issue.

2. Selective Updates: If you’re managing critical servers, consider configuring Yum Cron to only apply security updates (update_cmd = security) instead of all updates. This approach minimizes the risk of stability issues.

3. Test on Staging Servers: For production environments, use Yum Cron to test updates on a staging server before deploying to production. This can help identify any potential issues early.