[Unit]
Description=Regenerate SSH host keys

[Service]
Type=oneshot
ExecStartPre=/bin/sh -c "if [ -e /dev/hwrng ]; then dd if=/dev/hwrng of=/dev/urandom count=1 bs=4096; fi"
ExecStart=/usr/bin/ssh-keygen -A
ExecStartPost=/bin/rm /lib/systemd/system/regenerate_ssh_host_keys.service ; /usr/sbin/update-rc.d regenerate_ssh_host_keys remove

[Install]
WantedBy=multi-user.target