Upgrading Ubuntu 20.04 → 24.04 and PHP 7.4 → PHP 8.3 (Apache + WordPress)

This guide walks through a real-world, production-safe upgrade path:

• Ubuntu 20.04 → 22.04 → 24.04
• PHP 7.4 → 8.3
• Apache using mpm_event + PHP-FPM
• WordPress-safe PHP extensions
• Avoids Ubuntu Pro / ESM blockers

0. Pre-flight checklist (DO NOT SKIP)

lsb_release -a
php -v
apachectl -M | egrep 'mpm|php'

Backups:

• VM snapshot (or image)
• /etc
• /var/www
• Databases

1. Clean up old PHP 7.4 packages (critical)

Leftover PHP 7.4 packages will block upgrades.

sudo apt purge -y \
  php7.4\* libapache2-mod-php7.4

sudo apt autoremove -y
sudo apt autoclean

Confirm nothing 7.4 remains:

apt list --installed | grep php7.4 || echo "PHP 7.4 removed"

2. Fully update Ubuntu 20.04 (ignore Ubuntu Pro warnings)

You do not need Ubuntu Pro to upgrade releases.

sudo apt update
sudo apt full-upgrade -y
sudo reboot

If you see “security updates require Ubuntu Pro”, that’s fine — they are not blockers for release upgrades.

3. Upgrade Ubuntu 20.04 → 22.04

sudo do-release-upgrade

• Choose keep local version when prompted for everything except Chrony
• Reboot when finished

Verify:

lsb_release -a

4. Upgrade Ubuntu 22.04 → 24.04

sudo apt update
sudo apt full-upgrade -y
sudo do-release-upgrade
sudo reboot

Verify:

lsb_release -a
# Should show 24.04.x

5. Install PHP 8.3 (WordPress-safe stack)

Ubuntu 24.04 ships PHP 8.3 natively.

sudo apt install -y \
  php8.3 php8.3-fpm php8.3-cli php8.3-common \
  php8.3-mysql php8.3-curl php8.3-gd php8.3-imagick \
  php8.3-intl php8.3-mbstring php8.3-xml php8.3-zip \
  php8.3-bcmath php8.3-soap php8.3-opcache

Verify:

php -v

6. Switch Apache to mpm_event + PHP-FPM (recommended)

Disable prefork + mod_php:

sudo a2dismod php7.4 php8.3 mpm_prefork

Enable event + proxy modules:

sudo a2enmod mpm_event proxy_fcgi setenvif
sudo a2enconf php8.3-fpm

Restart:

sudo systemctl restart php8.3-fpm
sudo systemctl restart apache2

Confirm:

apachectl -M | egrep 'mpm|fcgi'

You should see:

• mpm_event
• proxy_fcgi

7. Set PHP upload limits (CLI + FPM)

Create a single override file.

PHP-FPM (used by Apache / WordPress)

sudo tee /etc/php/8.3/fpm/conf.d/99-uploads.ini > /dev/null <<'EOF'
upload_max_filesize = 128M
post_max_size = 128M
memory_limit = 256M
max_execution_time = 300
EOF

sudo systemctl restart php8.3-fpm
sudo systemctl reload apache2

PHP CLI (optional but recommended)

sudo tee /etc/php/8.3/cli/conf.d/99-uploads.ini > /dev/null <<'EOF'
upload_max_filesize = 128M
post_max_size = 128M
memory_limit = 256M
max_execution_time = 300
EOF

Verify FPM:

sudo php-fpm8.3 -i | egrep 'upload_max_filesize|post_max_size|memory_limit|max_execution_time'

8. Security hardening (quick wins)

Disable CGI if not needed:

sudo a2disconf serve-cgi-bin
sudo systemctl reload apache2

Blocking xmlrpc.php and /server-status errors in logs is expected and healthy for WordPress.

9. Final verification checklist

php -v
apachectl -M | egrep 'mpm|php|fcgi'
systemctl status php8.3-fpm --no-pager

WordPress:

• Media uploads work
• Plugins update correctly
• No raw PHP output

Notes on PHP versions

• PHP 8.3 is the correct, stable target for Ubuntu 24.04
• PHP 8.4 exists but is not recommended yet for WordPress production
• Stick to 8.3 until WordPress core officially endorses 8.4

TL;DR

✔ Purge PHP 7.4 ✔ apt full-upgrade before every release jump ✔ Upgrade 20 → 22 → 24, never skip ✔ Use mpm_event + PHP-FPM ✔ Set limits in FPM, not just CLI