Modify the file
/etc/systemd/system/getty.target.wants/getty@tty1.service
which is a symlink to
/lib/systemd/system/getty@service

change the line

ExecStart=-/sbin/agetty --noclear %I $TERM

into

ExecStart=-/sbin/agetty -a username %I $TERM

... replace the "username" with appropriate one, works also with user root

... then reboot and all terminals will be logged in automatically