How do I force Postgres to respect the configuration file on service start? Or how can I assign shared_buffer and max_connections on boot?

 By default, Postgres will use the values specified in its configuration file when it starts up. However, there are a few things you can do to ensure that it respects the configuration file and uses the values you specify.

First, make sure that the configuration file is in the correct location and has the correct name. By default, the configuration file is named postgresql.conf and is located in the data directory. You can specify a different configuration file using the -D and -c options when starting the Postgres service.

Second, check the output of the Postgres service startup logs to see if there are any errors or warnings related to the configuration file. If there are errors or warnings, you will need to address those issues before the service will start using the values specified in the configuration file.

If you still have trouble getting Postgres to use the values specified in the configuration file, you can try explicitly setting the values using the -c option when starting the service. For example, to set the shared_buffers and max_connections parameters, you can use the following command:

sudo systemctl start postgresql -c "shared_buffers=512MB" -c "max_connections=100"

This will start the Postgres service with shared_buffers set to 512MB and max_connections set to 100. Note that this approach will override any values specified in the configuration file, so use it with caution.