Falta disponibilizar o arquivo doguito-site.service

https://github.com/alura-cursos/doguito-site-orm/blob/master/doguito-api.service

# https://docs.oracle.com/en/learn/use_systemd/index.html#introduction
# https://oracle-base.com/articles/linux/linux-services-systemd#creating-linux-services
# https://nodesource.com/blog/running-your-node-js-app-with-systemd-part-1/

[Unit]
Description=Doguito API Service
After=network.target

[Service]
Environment="DB_USER=ADMIN"
Environment="DB_PASSWORD=???"
Environment="CONNECT_STRING=???"
Type=simple
User=opc
ExecStart=/usr/bin/node /home/opc/doguito-api/bin/www
Restart=on-failure

[Install]
WantedBy=multi-user.target

esse aí é doguito-api.service e não doguito-site.service. tá correto?

# https://docs.oracle.com/en/learn/use_systemd/index.html#introduction
# https://oracle-base.com/articles/linux/linux-services-systemd#creating-linux-services
# https://nodesource.com/blog/running-your-node-js-app-with-systemd-part-1/

[Unit]
Description=Doguito API Service
After=network.target

[Service]
Environment="DB_USER=ADMIN"
Environment="DB_PASSWORD=????"
Environment="CONNECT_STRING=?????"
Type=simple
User=opc
ExecStart=/usr/bin/node /home/opc/doguito-site-orm/bin/www
Restart=on-failure

[Install]
WantedBy=multi-user.target

David, é quase o mesmo arquivo... quase...

O que muda:

• Environment="DB_PASSWORD=????"

• Environment="CONNECT_STRING=?????"

• ExecStart=/usr/bin/node /home/opc/doguito-site-orm/bin/www

Essas linhas mudam a depender do seu projeto final