Handle serial console better

roles/home-cli/files/bhyve-vm

@@ -45,8 +45,8 @@ ram=1G
 # from this host (or via SSH tunnels).
 vnchost="127.0.0.1"
 
-# Change to /dev/nmdm0A for the first null-modem, or stdio.
-comoutput=/dev/nmdm${vmnumber}A
+# Uncomment to use stdio for the serial console.
+#comoutput=stdio
 
 # Comment the next line out for no CD-ROM.
 #cdrom="-s 3,ahci-cd,$vmpath/cdrom.iso"
@@ -78,7 +78,7 @@ fi
 	-s 29,fbuf,tcp=$vnc:590$vmnumber,w=800,h=600 \
 	-s 30,xhci,tablet \
 	-s 31,lpc \
-	-l com1,$comoutput \
+	-l com1,${comoutput:-/dev/nmdm${vmnumber}A} \
 	-l bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI.fd \
 	$vmname
 /usr/sbin/bhyvectl --destroy --vm=$vmname