armbian-firstrun: Optionally skip OpenSSH host key regeneration

packages/bsp/common/etc/default/armbian-firstrun.dpkg-dist

@@ -0,0 +1,6 @@
+# configuration values for the armbian-firstrun service
+
+# Delete + regenerate OpenSSH host keys
+# true  = delete + generate host keys
+# false = no deletion / no generation for host keys
+OPENSSHD_REGENERATE_HOST_KEYS=true

packages/bsp/common/lib/systemd/system/armbian-firstrun.service

@@ -10,6 +10,7 @@ After=ssh.service
 [Service]
 Type=simple
 RemainAfterExit=yes
+EnvironmentFile=/etc/default/armbian-firstrun
 ExecStart=/usr/lib/armbian/armbian-firstrun start
 TimeoutStartSec=2min
 

packages/bsp/common/usr/lib/armbian/armbian-firstrun

@@ -46,12 +46,16 @@ case "$1" in
 	[[ -f /etc/systemd/system/armbian-live-patch.service ]] && systemctl --no-reload enable armbian-live-patch.service
 
 	# SSH Keys creation
-	rm -f /etc/ssh/ssh_host*
-	read entropy_before </proc/sys/kernel/random/entropy_avail
-	dpkg-reconfigure openssh-server >/dev/null 2>&1
-	service ssh restart
-	read entropy_after </proc/sys/kernel/random/entropy_avail
-	echo -e "\n### [firstrun] Recreated SSH keys (entropy: ${entropy_before} ${entropy_after})" >>${Log}
+	if [[ "${OPENSSHD_REGENERATE_HOST_KEYS}" = true ]]; then
+		rm -f /etc/ssh/ssh_host*
+		read entropy_before </proc/sys/kernel/random/entropy_avail
+		dpkg-reconfigure openssh-server >/dev/null 2>&1
+		service ssh restart
+		read entropy_after </proc/sys/kernel/random/entropy_avail
+		echo -e "\n### [firstrun] Recreated SSH keys (entropy: ${entropy_before} ${entropy_after})" >>${Log}
+	else
+		echo -e "\n### [firstrun] SSH host keys unchanged" >>${Log}
+	fi
 
 	# get rid of purple background color in newt apps whiptail, partimage, debconf ... Reverting to Debian look.
 	[[ -f /etc/newt/palette ]] && sed -e 's/magenta/blue/g' -i /etc/newt/palette