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Q: Interacting with a program running as part of a systemd service Ive got a systemd service set up with the following configuration (in /etc/systemd/system/my-service.service):
[Unit]
Description=My service

[Service]
WorkingDirectory=/path/to/my/service
User=some-user
Group=some-group
Restart=on-failure
RestartSec=20 5
ExecStart=my-service-binary

[Install]
WantedBy=multi-user.target

When the program is started, it provides a command line interface to allow interaction. However, as this program is run by systemd, I cant immediately see a way to interact with the program directly. Is there some way to connect to the stream the program provides, while running it as a service within systemd?

A: In man systemd.exec, youll find that you can set StandardInput= to a value of tty, and then set TTYPath= to set a particularly TTY to connect to.
Its fairly unconventional to use systemd to run CLI apps though.
Some services may appear to run via systemd and offer a CLI, but they are really using a client/server model. For example, database servers are typically run via systemd, but you connect to them via CLI when they are running.
How the client/server interaction works is specific to each server. Usually they are communicating over a local port or socket.
You should first confirm if the service you running is designed to connect directly to a TTY or whether it actually listening a local port or socket that a CLI-based client connects to.

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