Centos 7 Install Ssl Certificate

admin14 April 2024Last Update :

Understanding SSL Certificates and Their Importance

SSL (Secure Sockets Layer) certificates are digital certificates that provide a secure, encrypted connection between a web server and a client’s web browser. They are essential for protecting sensitive data in transit, such as personal information, credit card numbers, and login credentials. By installing an SSL certificate on your CentOS 7 server, you ensure that all data transferred to and from your website is secure from eavesdroppers and potential attackers.

Prerequisites for Installing an SSL Certificate on CentOS 7

  • A registered domain name.
  • A CentOS 7 server with root or sudo privileges.
  • A web server like Apache or Nginx installed on your CentOS 7 system.
  • The mod_ssl module for Apache or the equivalent for other web servers.
  • An SSL certificate, which can be purchased from a Certificate Authority (CA) or obtained for free from Let’s Encrypt.

Step-by-Step Guide to Install an SSL Certificate on Apache

Obtaining an SSL Certificate

Before installing an SSL certificate, you must first obtain one. You can purchase a certificate from a CA or get a free one from Let’s Encrypt using tools like Certbot. For this guide, we’ll assume you have already acquired an SSL certificate and have received the following files:

  • certificate.crt: Your primary SSL certificate file.
  • private.key: The private key generated when you created the CSR (Certificate Signing Request).
  • ca_bundle.crt: The chain of intermediate certificates that establish trust for your SSL certificate.

Installing mod_ssl on Apache

To use SSL with Apache, you need to install the mod_ssl module. Use the following command to install it:

yum install mod_ssl

Configuring Apache to Use the SSL Certificate

Once you have your SSL certificate files, you need to upload them to your server. A common practice is to place them in the /etc/ssl/certs directory for certificates and /etc/ssl/private for private keys, ensuring that the private key file is not world-readable.

Next, configure your Apache virtual host to use the SSL certificate. Edit the SSL configuration file, typically located at /etc/httpd/conf.d/ssl.conf, or create a new configuration file for your site within the /etc/httpd/conf.d/ directory.

Here’s an example of what your virtual host configuration might look like:

<VirtualHost *:443>
    ServerName www.yourdomain.com
    DocumentRoot /var/www/html

    SSLEngine on
    SSLCertificateFile /etc/ssl/certs/certificate.crt
    SSLCertificateKeyFile /etc/ssl/private/private.key
    SSLCertificateChainFile /etc/ssl/certs/ca_bundle.crt

    <Directory "/var/www/html">
        AllowOverride All


After making changes to the Apache configuration, restart the service to apply the new settings:

systemctl restart httpd

Step-by-Step Guide to Install an SSL Certificate on Nginx

Preparing the SSL Certificate Files

For Nginx, you often need to concatenate the primary certificate and the intermediate certificates into a single file. This can be done using the cat command:

cat certificate.crt ca_bundle.crt > ssl-bundle.crt

Move the resulting ssl-bundle.crt and your private.key to the appropriate directories, commonly /etc/nginx/ssl/.

Configuring Nginx to Use the SSL Certificate

Edit your Nginx server block configuration, usually found in /etc/nginx/conf.d/ or /etc/nginx/sites-available/, to include the SSL settings. Below is an example configuration:

server {
    listen 443 ssl;
    server_name www.yourdomain.com;

    ssl_certificate /etc/nginx/ssl/ssl-bundle.crt;
    ssl_certificate_key /etc/nginx/ssl/private.key;

    location / {
        root /usr/share/nginx/html;
        index index.html index.htm;

Reload Nginx to activate the SSL certificate:

systemctl reload nginx

Verifying the SSL Installation

After installing your SSL certificate, it’s crucial to verify that it’s working correctly. You can do this by accessing your website using https:// in front of your domain name. If the installation was successful, you should see a padlock icon next to your URL, indicating a secure connection.

Additionally, you can use online tools like SSL Labs’ SSL Test to check for any issues and confirm that your server is configured securely.

Troubleshooting Common SSL Installation Issues

If you encounter problems after installing your SSL certificate, here are some common issues and their solutions:

  • Incorrect File Permissions: Ensure that your private key file is readable only by the root user for security reasons.
  • Apache/Nginx Configuration Errors: Double-check your configuration files for any syntax errors or incorrect paths to your SSL certificate files.
  • Firewall Settings: Make sure that port 443 (the default port for HTTPS traffic) is open on your firewall.
  • SELinux Contexts: If SELinux is enforcing, ensure that the correct contexts are set for your certificate files.

Automating SSL Renewals with Certbot

If you’re using a Let’s Encrypt SSL certificate, you can automate the renewal process using Certbot. After initially obtaining your certificate with Certbot, you can set up a cron job to automatically renew the certificate before it expires.

0 3 * * * /usr/bin/certbot renew --quiet

This cron job will run daily at 3 AM, checking if the certificate is due for renewal and renewing it if necessary.

FAQ Section

Can I install an SSL certificate without a dedicated IP address?

Yes, thanks to Server Name Indication (SNI), modern web servers like Apache and Nginx allow multiple SSL certificates to be hosted on a single IP address.

How do I redirect HTTP traffic to HTTPS on my web server?

You can set up a redirection rule in your web server configuration. For Apache, use the RewriteEngine, and for Nginx, use the return directive within a server block listening on port 80.

What is the difference between a self-signed certificate and one issued by a CA?

A self-signed certificate provides encryption but isn’t trusted by browsers and clients by default, leading to security warnings. A CA-issued certificate is globally trusted and doesn’t produce such warnings.

How long does an SSL certificate last?

SSL certificates issued by CAs typically last for 1-2 years, while Let’s Encrypt certificates are valid for 90 days. Both types require renewal upon expiration.

Is it possible to install an SSL certificate on CentOS 7 without a control panel?

Yes, you can manually install an SSL certificate on CentOS 7 using the command line, as outlined in this article.


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