When encountering a "ConnectionRefused" error, the most direct meaning is that the target host or service you are trying to connect to explicitly reject your request. 1. Check whether the target service is running, log in to the target machine to check the service status using systemctlstatus or psaux, and start manually if it is not started; 2. Confirm whether the port is listening correctly, use netstat or ss command to check whether the service is listening to the correct port, modify the configuration file if necessary and restart the service; 3. Firewall and security group settings may cause connection denied, check the local firewall rules and cloud platform security group configuration, and temporarily close the firewall during testing; 4. IP address or DNS resolution errors may also cause problems, use ping or

Enabling KeepAlive can significantly improve website performance, especially for pages that load multiple resources. It reduces connection overhead and speeds up page loading by keeping the browser and server connection open. If the site uses a large number of small files, has duplicate visitors, or attaches importance to performance optimization, KeepAlive should be enabled. When configuring, you need to pay attention to setting a reasonable timeout time and number of requests, and test and verify its effect. Different servers such as Apache, Nginx, etc. all have corresponding configuration methods, and you need to pay attention to compatibility issues in HTTP/2 environments.

To improve Apache performance, optimize configuration parameters are required. 1. Adjust KeepAlive parameters: Enable MaxKeepAliveRequests and set to 500 or higher, and set KeepAliveTimeout to 2~3 seconds to reduce connection overhead. 2. Configure the MPM module: Set StartServers, MinSpareServers, MaxSpareServers and MaxClients in prefork mode; set ThreadsPerChild and MaxRequestWorkers in event or worker mode to avoid excessive load. 3. Control memory usage: based on the memory usage of a single process

Apache's default web root directory is /var/www/html in most Linux distributions. This is because the Apache server provides files from a specific document root directory. If the configuration is not customized, systems such as Ubuntu, CentOS, and Fedora use /var/www/html, while macOS (using Homebrew) is usually /usr/local/var/www, and Windows (XAMPP) is C:\xampp\htdocs; to confirm the current path, you can check the Apache configuration file such as httpd.conf or apache2.conf, or create a P with phpinfo()

To improve Apache security, we need to start from module management, permission control, SSL encryption, log monitoring, etc. 1. Close unnecessary modules such as mod_imap, mod_info, etc., and make use of the LoadModule line and restart the service to take effect; 2. Set the root directory permissions to 755 or below, restrict write permissions, and disable directory traversal and script execution in the configuration; 3. Enable HTTPS, use Let'sEncrypt certificate and disable the old version of the protocol and weak encryption suite; 4. Check the access and error logs regularly, combine fail2ban to block abnormal IP, and use IP restrictions on sensitive paths.

Enable HSTS to force browsers to access websites through HTTPS, improving security. 1. To enable HTTPS in Apache, you must first configure HTTPS, and then add Strict-Transport-Security response header in the site configuration file or .htaccess; 2. To configure max-age (such as 31536000 seconds), includeSubDomains and preload parameters; 3. Make sure that the mod_headers module is enabled, otherwise run sudoa2enmodheaders and restart Apache; 4. You can optionally submit to the HSTSPreload list, but it must satisfy that both the main site and the subdomain support HTTPS.

The steps to install Apache on Ubuntu or Debian include: 1. Update the system software package to ensure the latest software source; 2. Run sudoaptininstallapache2 to install the Apache service and check its running status; 3. Configure the firewall to allow HTTP/HTTPS traffic; 4. Adjust the website file path, modify the configuration or enable the module as needed; 5. Restart the Apache service after modifying the configuration and taking effect. The whole process is simple and direct, but you need to pay attention to key points such as permission settings, firewall rules and configuration adjustments to ensure that Apache works normally and can access the default page through the browser.

To redirect a non-www domain name to www or vice versa, it can be achieved through server configuration, CDN or hosting platform. 1. Apache server: Use the .htaccess file to add RewriteCond and RewriteRule rules, and set 301 redirection; 2. Nginx server: modify the site configuration file and use the return301 instruction to achieve jump; 3. CDN or hosting platform: for example, Cloudflare creates page rules to jump. Notes include ensuring that the SSL certificate covers two domain names, testing whether the jump takes effect, and maintaining the consistency of the entire site link to avoid SEO issues and access errors.