.TL
Automatically Launch Applications on tty
.AU
tropf
.AB
Rundown on how to start an interactive console application
automatically on boot using systemd.
Useful for unattended Raspberry Pis.
.AE
.DA
.
.NH 1
General Idea
.PP
By default the service
.CW "getty"
is launched.
That will do the magic that opens a login prompt on any tty.
.
.PP
To automatically launch an application instead of that login prompt,
one has to
.I "simply"
overwrite that behaviour.

.NH 1
Create A New Service
.PP
Create a file named
.CW "/etc/systemd/system/mytui@.service" "."
.
.CB
[Unit]
Description=Custom user interface on %I
Documentation=https://unix.stackexchange.com/a/318336/5132
Conflicts=getty@%I.service
Before=getty.target

[Service]
ExecStart=/usr/local/bin/mytui
StandardInput=tty
StandardOutput=tty
Restart=always
RestartSec=1
UtmpIdentifier=%I
TTYPath=/dev/%I
TTYReset=yes
TTYVHangup=yes
TTYVTDisallocate=yes
SendSIGHUP=yes

[Install]
WantedBy=multi-user.target
.CE
.
.PP
Obviuosly adjust the filename and the
.CW "ExecStart"
parameter.
.
.NH 1
Start Your New Service On Boot
.NH 2
Enablind The Service
.PP
Simply enable your new service:
.CB
systemctl enable mytui@tty1.service
.CE
.
.PP
.CW "tty1"
works for debian.
It also has to be
.CW "tty1"
as this is the one that will be selected by default.
.
.PP
Launching on
.CW "tty2"
would require switching to that tty after boot,
and that would be the opposite of "unattended".
.
.NH 2
Preventing The Default Behaviour
.PP
Prevent systemd from starting the
.CW "getty"
.I "at the same time on the same tty" ":"
.CB
systemctl mask getty@tty1.service
.CE