[Unit]
Description=SSH Key Generation
ConditionPathExists=|!/etc/dropbear/dropbear_rsa_host_key

[Service]
ExecStart=/usr/sbin/dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target