systemd-first-boot-script/scripts/01-renew-ssh-keys

#!/bin/bash
# Licence : GPL v3
# Author: Laurent HUBERT
#
# Renews the ssh server keys if they exist
#
cat <<EOF
+---------------------------------------------+
| Renewing SSH server keys                    |
+---------------------------------------------+
EOF
status=0
renew_ssh_keys(){
  rm /etc/ssh/ssh_host_*key*
  dpkg-reconfigure openssh-server
  status=$?
}
# Disables to avoid error messages
systemctl disable ssh
systemctl stop ssh

ls /etc/ssh/ssh_host_*key* > /dev/null 2>&1 && renew_ssh_keys || status=1

systemctl enable ssh
systemctl start ssh

if [ 0 -ne "$status" ]
then
  # Exit with non zero status
  echo "### Error renewing SSH keys    ###"
  exit 1
else
  echo "> Renewing SSH server keys : OK               <"
  systemctl start ssh
  exit 0
fi