Goal

Execute an interactive script on tty2 (using dialog) at boot with systemd.

Files

/usr/lib/systemd/system/simple-window-dialog.service:

[Unit]
Description=Simple interactive dialog window
After=getty@tty2.service

[Service]
Type=oneshot
ExecStart=/usr/bin/dialog-hello.sh
StandardInput=tty
TTYPath=/dev/tty2
TTYReset=yes
TTYVHangup=yes

[Install]
WantedBy=default.target

/usr/bin/dialog-hello.sh (add execution permission):

#!/bin/bash

sleep 5

chvt 2

dialog --msgbox "Hello world!" 10 40

Enable the systemd service

# systemctl enable simple-window-dialog.service

Or

# ln -sf /usr/lib/systemd/system/simple-window-dialog.service /usr/lib/systemd/system/default.target.wants/simple-window-dialog.service

Run

Reboot (if the systemd setup is correct you should see the dialog window) enjoy.