this issue was raised previously by another user some time ago and was caused by a different means to my find today, however, the issue clearly has never been correctly resolved and causes considerable problems for the Virtualmin system.
The reason it is such a huge problem...it takes out the entire server php-fpm x.x operations for any and all virtual servers using the same version of php-fpm!
Here is how i struck the issue (and i have encountered this twice in 3 days)
Virtualmin>Server Configuration> Move Virtual Server
i moved an existing virtual server wordpress.domain.com from a primary virtual server underneath a parent server with the same domain name (ie domain.com).
Virtualmin moved the server no problem, however as soon as it completes the move and then attempts to restart php-fpmx.x the php-fpm server fails to restart because it exited with an error code.
In checking the php.conf file for the new Virtual Sub Server wordpress.domain.com i have just created, i then goto...
virtualmin>Services>PHP-FPM Configuration>Edit Configuration Manually
It displays the following
user = flystanwell.com
group = wordpress
listen = 8012
pm = ondemand
pm.max_children = 20
pm.start_servers = 1
pm.min_spare_servers = 1
pm.max_spare_servers = 5
php_admin_value[upload_tmp_dir] = /home/wordpress/tmp
php_admin_value[session.save_path] = /home/wordpress/tmp
php_value[memory_limit] = 16M
php_value[session.save_path] = /home/wordpress/tmp
php_value[max_execution_time] = 180
php_admin_value[upload_max_filesize] = 32M
php_admin_value[post_max_size] = 32M
The error is in the second line
group = wordpress
this group does not exist in Webmin!
The fix (which i have found on another forum/blogg is to change that line to read...
group = domain.com (where domain.com is a group the parent virtual server belongs too and which actually exists in Webmin)
This is a critical fix that needs urgently resolving as anyone who moves virtual servers (or migrates cpanel accounts where there is the possibility of similar domain names) will find that this bug will take out their entire php-fpm server (it will stop working until the error is fixed manually as i outline above). What is worse, if the user than changes the php-fpm version for the new virtual server where the group is wrong...it will also take out that php-fpm version as well. I ended up with all of my php-fpm servers offline (and thus all server websites running on php-fpm stopped functioning as well).
Dont forget to goto Virtualmin>Server Configuration>Website Options and just click "Save" (this will restart php-fpm for this virtual server and it should start working again)
I hope this workaround is something that others find useful.