I’m not too entirely sure what you’re asking.
The mongod service is the default service the installation script has. The link provided should be the way I installed it.
/usr/lib/systemd/system/mongod.service file
[Unit]
Description=MongoDB Database Server
Documentation=https://docs.mongodb.org/manual
After=network-online.target
Wants=network-online.target
[Service]
User=mongodb
Group=mongodb
EnvironmentFile=-/etc/default/mongod
Environment="MONGODB_CONFIG_OVERRIDE_NOFORK=1"
ExecStart=/usr/bin/mongod --config /etc/mongod.conf
RuntimeDirectory=mongodb
# file size
LimitFSIZE=infinity
# cpu time
LimitCPU=infinity
# virtual memory size
LimitAS=infinity
# open files
LimitNOFILE=64000
# processes/threads
LimitNPROC=64000
# locked memory
LimitMEMLOCK=infinity
# total threads (user+kernel)
TasksMax=infinity
TasksAccounting=false
# Recommended limits for mongod as specified in
# https://docs.mongodb.com/manual/reference/ulimit/#recommended-ulimit-settings
[Install]
WantedBy=multi-user.target