regenerate_ssh_host_keys.service

[Unit]
Description=Regenerate SSH host keys
Before=ssh.service

[Service]
Type=oneshot
ExecStartPre=-/bin/dd if=/dev/hwrng of=/dev/urandom count=1 bs=4096
ExecStartPre=-/bin/sh -c "/bin/rm -f -v /etc/ssh/ssh_host_*_key*"
ExecStart=/usr/bin/ssh-keygen -A -v
ExecStartPost=/bin/systemctl disable regenerate_ssh_host_keys

[Install]
WantedBy=multi-user.target