in-place upgrade Ubuntu 22.04 web server to Ubuntu 24.04

One of our web servers was running Ubuntu 22.04 and showed that an upgrade was available via 'do-release-upgrade'

I took the plunge, running the upgrade via screen in case our connection broke. (The upgrade process also auto-starts sshd on port 1022 also, in case the upgrade needs recovery. But thankfully, I didn't need it.)

Chose the default options every time for retaining the configuration files. Noticed that apache showed a "syntax error" in config files.

After the restart, checked apache status with

sudo systemctl status apache2

× apache2.service - The Apache HTTP Server

     Loaded: loaded (/usr/lib/systemd/system/apache2.service; enabled; preset: enabled)

     Active: failed (Result: exit-code) since Sat 2026-06-06 04:18:46 UTC; 1min 46s ago

       Docs: https://httpd.apache.org/docs/2.4/

    Process: 797 ExecStart=/usr/sbin/apachectl start (code=exited, status=1/FAILURE)

        CPU: 28ms

Jun 06 04:18:45 sssihms-web-vm2023 systemd[1]: Starting apache2.service - The Apache HTTP Server...

Jun 06 04:18:45 sssihms-web-vm2023 apachectl[821]: apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 3 of /etc/apache2/mods-enabled/php8.1.load:>

Jun 06 04:18:46 sssihms-web-vm2023 systemd[1]: apache2.service: Control process exited, code=exited, status=1/FAILURE

Jun 06 04:18:46 sssihms-web-vm2023 systemd[1]: apache2.service: Failed with result 'exit-code'.

Jun 06 04:18:46 sssihms-web-vm2023 systemd[1]: Failed to start apache2.service - The Apache HTTP Server.

Claude pointed out that Ubuntu 24.04 has php8.3, so loading php8.1 would fail. So, 

sudo a2dismod php8.1

# Install php8.3

sudo apt install php8.3 libapache2-mod-php8.3

# this had already been installed during the upgrade

# Enable the new module

sudo a2enmod php8.3

sudo systemctl restart apache2

All good. Wordpress is also running fine.