AWS EC2 Ubuntu16.04部署Apache2后无法访问问题求助

Alright, let's walk through the most likely reasons your Apache2 default site isn't accessible on your Ubuntu 16.04 EC2 instance—even with port 80 allowed in security groups:

• Apache2 isn't actually listening on port 80
  Just because Apache is running doesn't mean it's bound to port 80. Verify this with:

  sudo netstat -tulpn | grep apache2
  

  Or if netstat isn't installed, use:

  ss -tulpn | grep apache2
  

  If you don't see :80 in the output, check Apache's port config at /etc/apache2/ports.conf (ensure it has Listen 80) and the default site config at /etc/apache2/sites-available/000-default.conf (confirm <VirtualHost *:80> is set). Fix any issues, then restart Apache:

  sudo systemctl restart apache2
  

• Ubuntu's UFW firewall is blocking port 80
  AWS security groups are great, but Ubuntu's built-in UFW firewall can still block incoming traffic even if the security group allows it. Check UFW's status:

  sudo ufw status
  

  If port 80 isn't listed as allowed, add the rule:

  sudo ufw allow 80/tcp
  

  Double-check the status to confirm the rule is active.

• Your EC2 instance isn't in a public subnet
  The public DNS you're using (ec2-3-231-162-52.compute-1.amazonaws.com) maps to a public IP, but your instance needs to be in a public subnet to be reachable from the internet. A public subnet has a route table entry pointing to an Internet Gateway (IGW). If your instance is in a private subnet, you'll need to set up a load balancer or move it to a public subnet to access it directly.

• The Apache2 default site isn't enabled
  While Ubuntu 16.04 usually enables the default site automatically during installation, it's worth verifying:

  sudo a2query -s
  

  If 000-default isn't listed, enable it with:

  sudo a2ensite 000-default.conf
  

  Then restart Apache to apply the change.

• VPC Network ACLs are blocking traffic
  Network ACLs (NACLs) are a second layer of firewall in AWS VPCs. Unlike security groups, they're stateless, so you need to allow both incoming port 80 traffic and outgoing response traffic (typically TCP ports 1024-65535). Head to the AWS VPC console, find the NACL attached to your instance's subnet, and confirm:

  • Inbound rules allow 0.0.0.0/0 on TCP port 80
  • Outbound rules allow 0.0.0.0/0 on TCP ports 1024-65535

• Apache2 has configuration errors or file permission issues
  Even if Apache is running, misconfigurations or permission problems can break access. Check the Apache error log for clues:

  sudo tail -f /var/log/apache2/error.log
  

  Common issues include syntax errors in config files, or incorrect permissions on the default web root (/var/www/html). Ensure the www-data user has read access to files in this directory:

  sudo chown -R www-data:www-data /var/www/html
  

内容的提问来源于stack exchange，提问作者Peter Szabo