Change Apache MPM from prefork to worker

Question

I need to change MPM prefork module to worker but it's not working on my Debian 9.1. When I enable worker module, PHP is not working. I can't enable php7.0 module back.

Here is the output from console:

root@Debian-91-stretch-64-LAMP ~ # apachectl -V | grep -i mpm

AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 2a01:4f8:171:fc2::2. Set the 'ServerName' directive globally to suppress this message

Server MPM: prefork

root@Debian-91-stretch-64-LAMP ~ # a2enmod mpm_worker

Considering conflict mpm_event for mpm_worker: Considering conflict mpm_prefork for mpm_worker: ERROR: Module mpm_prefork is enabled - cannot proceed due to conflicts. It needs to be disabled first!

root@Debian-91-stretch-64-LAMP ~ # a2dismod mpm_prefork

ERROR: The following modules depend on mpm_prefork and need to be disabled first: php7.0 root@Debian-91-stretch-64-LAMP ~ # a2dismod php7.0 Module php7.0 disabled.

To activate the new configuration, you need to run:

systemctl restart apache2

root@Debian-91-stretch-64-LAMP ~ # a2dismod php7.0

Module php7.0 disabled.

To activate the new configuration, you need to run:

systemctl restart apache2

root@Debian-91-stretch-64-LAMP ~ # a2enmod mpm_worker

Considering conflict mpm_event for mpm_worker:

Considering conflict mpm_prefork for mpm_worker:

Enabling module mpm_worker.

To activate the new configuration, you need to run:

systemctl restart apache2

root@Debian-91-stretch-64-LAMP ~ # a2enmod php7.0

Considering dependency mpm_prefork for php7.0:

Considering conflict mpm_event for mpm_prefork:

Considering conflict mpm_worker for mpm_prefork:

ERROR: Module mpm_worker is enabled - cannot proceed due to conflicts. It needs to be disabled first!

ERROR: Could not enable dependency mpm_prefork for php7.0, aborting

Solution

I got the following error

sudo a2enmod php7.2 
Considering dependency mpm_prefork for php7.2:
Considering conflict mpm_event for mpm_prefork:
ERROR: Module mpm_event is enabled - cannot proceed due to conflicts. It needs to be disabled first!
Considering conflict mpm_worker for mpm_prefork:
ERROR: Could not enable dependency mpm_prefork for php7.2, aborting

And to fix I simply did

sudo a2dismod mpm_event
sudo a2enmod php7.2
sudo systemctl restart apache2

you might also want to try restarting your server