How To Install WHMCS Billing System with Linux Plesk Control Panel

Critical Installation Notes

System Requirements

1. Preparation Steps

Domain Setup in Plesk

1. Log into the Plesk control panel
2. Navigate to Domains > Add Domain
3. Create a new subscription (e.g., billing.yourdomain.com)
4. Enable SSL using Let's Encrypt via SSL It! extension

PHP Configuration

# In Plesk panel:
1. Go to Domains > billing.yourdomain.com > PHP Settings
2. Set PHP version to 8.2
3. Enable required extensions:
   - curl
   - gd
   - imap
   - json
   - mysqli
   - xml
   - intl
   - soap
   - mbstring

Database Creation

# Via Plesk CLI
plesk bin database --create whmcs_db -domain billing.yourdomain.com -type mysql

Or via Plesk Panel:

1. Domains > billing.yourdomain.com > Databases
2. Add Database
3. Name: whmcs_db
4. Click OK

2. WHMCS Installation

Download and Extract WHMCS

# Connect via SSH
cd /var/www/vhosts/billing.yourdomain.com/httpdocs/
wget https://releases.whmcs.com/v2/pkgs/whmcs-8.10.1-release.1.zip
unzip whmcs-8.10.1-release.1.zip
rm whmcs-8.10.1-release.1.zip

Set File Permissions

# Set base permissions
find . -type f -exec chmod 644 {} \;
find . -type d -exec chmod 755 {} \;


# Set specific permissions
chmod 777 templates_c attachments downloads
chmod 400 configuration.php (update this permission when installing or activating your WHMCS license)

3. Security Configuration

Move Sensitive Directories

# Move directories outside web root
mv /var/www/vhosts/billing.yourdomain.com/httpdocs/templates_c/* /var/www/vhosts/billing.yourdomain.com/whmcs/templates_c/
mv /var/www/vhosts/billing.yourdomain.com/httpdocs/attachments/* /var/www/vhosts/billing.yourdomain.com/whmcs/attachments/
mv /var/www/vhosts/billing.yourdomain.com/httpdocs/downloads/* /var/www/vhosts/billing.yourdomain.com/whmcs/downloads/
mv /var/www/vhosts/billing.yourdomain.com/httpdocs/crons /var/www/vhosts/billing.yourdomain.com/whmcs/

Update Configuration

# Edit configuration.php
vim /var/www/vhosts/billing.yourdomain.com/httpdocs/configuration.php

# Add these lines:
$templates_compiledir = '/var/www/vhosts/billing.yourdomain.com/whmcs/templates_c';
$attachments_dir = '/var/www/vhosts/billing.yourdomain.com/whmcs/attachments';
$downloads_dir = '/var/www/vhosts/billing.yourdomain.com/whmcs/downloads';
$crons_dir = '/var/www/vhosts/billing.yourdomain.com/whmcs/crons';

4. Cron Job Configuration

via Plesk Panel:

1. Tools & Settings > Scheduled Tasks
2. Add Task
3. Run:

   /usr/bin/php -q /var/www/vhosts/billing.yourdomain.com/whmcs/crons/cron.php/pre>

4. Schedule: */5 * * * *

crontab -e
*/5 * * * * /usr/bin/php -q /var/www/vhosts/billing.yourdomain.com/whmcs/crons/cron.php

5. Plesk Integration

1. Log into WHMCS admin panel (https://billing.yourdomain.com/admin)
2. Navigate to Setup → Products/Services → Servers
3. Add New Server:
   • Name: Plesk Main Server
   • Hostname: server.yourdomain.com
   • Type: Plesk
   • Username: Admin username
   • Password: Admin password
   • Secure: Yes (use SSL)

6. Final Configuration Steps

PHP Settings in Plesk

# In PHP Settings:
session.save_path = /var/www/vhosts/billing.yourdomain.com/whmcs/sessions
date.timezone = UTC
memory_limit = 256M
max_execution_time = 300

Cleanup

# Remove installation files
rm -rf /var/www/vhosts/billing.yourdomain.com/httpdocs/install/

# Verify permissions
chmod 400 /var/www/vhosts/billing.yourdomain.com/httpdocs/configuration.php
find /var/www/vhosts/billing.yourdomain.com/whmcs/ -type d -exec chmod 755 {} \;

Common Issues and Solutions

# Reset permissions if needed
chown -R psaserv:psaserv /var/www/vhosts/billing.yourdomain.com/
find /var/www/vhosts/billing.yourdomain.com/httpdocs -type f -exec chmod 644 {} \;
find /var/www/vhosts/billing.yourdomain.com/httpdocs -type d -exec chmod 755 {} \;

# Verify MySQL service
systemctl status mysql

# Check database permissions
plesk bin database --list-user-privileges -domain billing.yourdomain.com

Maintenance Best Practices

• Configure daily backups through Plesk Backup Manager
• Monitor error logs in /var/www/vhosts/billing.yourdomain.com/logs/
• Regularly update WHMCS through the admin panel
• Keep Plesk and all PHP extensions updated