Ubuntu 18.04降级至16.04或解决Apache2上PHP运行问题

Hey there! Let's break down your two options clearly—downgrading to Ubuntu 16.04, or fixing the Apache-PHP issue on 18.04. I'd strongly recommend the second option since downgrading carries significant risks, but I'll cover both paths for you.

Option 1: Downgrade Ubuntu 18.04 to 16.04 (Not Recommended) #

Ubuntu doesn't officially support downgrading between major releases, so this process is prone to dependency conflicts, broken packages, or even a non-bootable system. Backup all critical data first—this is non-negotiable.

• First, back up your important files (home directory, configs, web content) to an external drive using a tool like tar:

  sudo tar -czvf /path/to/external/storage/server-backup.tar.gz /home /etc /var/www
  

• Update your apt sources to point to Ubuntu 16.04 (code name xenial) instead of 18.04 (bionic):

  sudo sed -i 's/bionic/xenial/g' /etc/apt/sources.list
  

• Refresh the package list and start the downgrade process:

  sudo apt update
  sudo apt dist-upgrade -y
  

• Once the process finishes, reboot your server:

  sudo reboot
  

Warning: If you encounter package conflicts during the downgrade, you may need to force remove problematic packages or even reinstall the system from scratch and restore your backup.

Option 2: Fix Apache2 PHP Execution on Ubuntu 18.04 (Recommended) #

This is the safer, more sustainable path. Let's troubleshoot common issues step by step:

• Install and enable the PHP Apache module: Ubuntu 18.04 ships with PHP 7.2 by default. Install the module and enable it:

  sudo apt install libapache2-mod-php7.2
  sudo a2enmod php7.2
  sudo systemctl restart apache2
  

• Test PHP parsing: Create a simple test file in your web root to verify PHP works:

  echo "<?php phpinfo(); ?>" | sudo tee /var/www/html/info.php
  

  Visit this file via your server's URL (e.g., http://your-server-ip/info.php). If you see a detailed PHP info page, parsing is working. If you see raw PHP code, the module isn't enabled properly.
• Check Apache configuration: Ensure Apache is set to handle .php files. Verify the php7.2.conf file has this rule:

  <FilesMatch ".+\.ph(p[3457]?|t|tml)$">
      SetHandler application/x-httpd-php
  </FilesMatch>
  

• If using PHP-FPM: If you prefer using PHP-FPM instead of mod_php, install and configure it:

  sudo apt install php7.2-fpm
  sudo a2enmod proxy_fcgi setenvif
  sudo a2enconf php7.2-fpm
  sudo systemctl restart apache2 php7.2-fpm
  

• Check error logs: If problems persist, dig into the logs for clues:
  • Apache error log: sudo tail -n 20 /var/log/apache2/error.log
  • PHP-FPM log (if applicable): sudo tail -n 20 /var/log/php7.2-fpm.log

内容的提问来源于stack exchange，提问作者pitwo