Orchid installers for all Linux distributions other than Ubuntu 14.04 use the systemd software suite to manage the Orchid Fusion VMS service.
The Orchid Fusion VMS systemd service is provided and fully configured by the Orchid Fusion VMS installer, but in certain circumstances it may be useful to modify the Fusion service to specify custom configuration options, such as increasing the maximum number of threads that Linux will allow Fusion to use (occasionally necessary for very large installations).
While it is possible (though not recommended) to modify Orchid Fusion VMS's service file directly at /etc/systemd/system/fusion.service, any modifications to this file will be overwritten with default values whenever Orchid Fusion VMS is upgraded. Follow the steps below to override or provide additional systemd options that will be persistent across upgrades:
Create an fusion.service.d directory parallel to your fusion.service file:
$ sudo mkdir -p /etc/systemd/system/fusion.service.d
Create a .conf file in this directory with the systemd variables (and sections) you need to add or override. For example, the following /etc/systemd/system/fusion.service.d/override.conf file can be used to increase the default OS resource limits for very large Fusion installations (200+ connected Orchid Core VMS servers):
After creating the override file, reload systemd and restart the Orchid Fusion VMS service for the change to take effect:
$ sudo systemctl daemon-reload
$ sudo systemctl restart fusion.service