SSH Permission Denied (publickey) Error — How to Fix

What Is SSH Permission Denied (publickey) Error — How to Fix? The this error usually appears when Web Servers cannot complete a request due to misconfiguration,...

What Is SSH Permission Denied (publickey) Error — How to Fix?

The this error usually appears when Web Servers cannot complete a request due to misconfiguration, resource limits, network issues, or a stopped service. Visitors see a failed page instead of your application. This guide explains the most common causes and shows step-by-step commands to diagnose and fix the problem on Linux servers.

In most cases the issue is on the origin server, not the CDN edge. Start with service status, logs, and firewall rules before changing application code.

Possible Causes

• Service stopped: Web Servers or a dependency (PHP-FPM, database) is not running.
• Firewall blocking: CSF, firewalld, ufw, or cloud security groups block required ports.
• High load: CPU, RAM, or disk I/O saturation prevents new connections.
• Wrong configuration: Invalid vhost, pool, or permission settings after an update.
• DNS / proxy mismatch: Origin IP or SSL mode does not match the live setup.
• Full disk or inode limit: Logs or cache cannot be written.

Solution Steps

Basic Checks via SSH

Connect to the server and verify services and listening ports.

# Service status
sudo systemctl status nginx
sudo systemctl status php-fpm
sudo systemctl status mysqld

# Listening ports
sudo ss -tlnp | grep -E ':80|:443|:3306'

# Resources
free -h
df -h
sudo journalctl -u nginx --no-pager -n 50

On Web Servers

Review error logs, test configuration, and restart only after a successful config test.

# Test config (example Nginx)
sudo nginx -t && sudo systemctl reload nginx

# Tail application logs
sudo tail -100 /var/log/nginx/error.log

Firewall and Cloudflare

Allow web ports and ensure proxy IPs are not blocked by fail2ban or WAF rules.

sudo firewall-cmd --list-all
sudo fail2ban-client status

Conclusion

After applying these steps, clear browser cache and test again. If the error persists, open a topic in our forum with the exact message, timestamp, and relevant log lines.

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