Whenever a daemon file is changed in /etc/systemd/system/, the daemon files must be reloaded with:

systemctl daemon-reload

Most *nix derivates start a login program such as getty on multiple virtual terminals for the user to log-in when the system boots. On pre-systemd systems, /etc/inittab was used to spawn (and re-spawn) getty on the virtual terminals, which could also be used to run console programs such as htop instead of the login terminal.

The procedure with systemd is a little different and involves shutting down the tty services and creating a service file. The first thing to do is run:

systemctl

and search (using forward-slash / and typing in text to search) for getty. On a Debian system, one would find:

  getty@tty1.service                                                          loaded active running   Getty on tty2       
  getty@tty2.service                                                          loaded active running   Getty on tty2            
  getty@tty6.service                                                          loaded active running   Getty on tty6       

which means that getty will be spawned on tty1, tty2 and tty6. Whilst tty6 has a special meaning and is a fallback console to always provide the means for an operator to log-in, tty1 and tty2 could be used to spawn a different program such as htop.

In order for getty and htop to not race each other, the first step is to stop and disable the getty@tty1.service service:

systemctl stop getty@tty1.service
systemctl disable getty@tty1.service

Next, add the following contents to a file placed at /etc/systemd/system/htop.service:

[Unit]
Description=htop on tty1

[Service]
Type=simple
ExecStart=/usr/bin/htop
StandardInput=tty
StandardOutput=tty
TTYPath=/dev/tty1
Restart=always
RestartSec=2

[Install]
WantedBy=getty.target

where:

• /dev/tty1 is the virtual terminal to start htop on.

You can now enable and start the service via:

systemctl enable htop.service
systemctl start htop.service

and htop should appear on the first virtual terminal.

The SystemD version of init 3:

systemctl isolate multi-user.target

and the init 4 version:

systemctl isolate graphical.target