VBoxManage command is very handy for managing virtual machines in servers running headless. Adding and removing forwarding rules is super simple, you just call for example
# adding "rule1" for "vm_1" mapping TCP host_port to guest_port VBoxManage modifyvm vm_1 --natpf1 "rule1,tcp,,host_port,,guest_port" # deleting that same rule VBoxManage modifyvm vm_1 --natpf1 delete rule1
I created two simple scripts so that I don’t have to remember the exact syntax every time: vm_forward_add and vm_forward_delete. You run the commands with no arguments, and they tell you what you need to add.
Listing the existing rules is a bit more complex, as
VBoxManage has no option for that (not the version that I use, at least).
This is where xmlstarlet comes to the rescue. Xmlstarlet is a command-line tool for parsing XML that comes pre-installed in most UNIX systems.
Since forwarding rules are stored in VirtualBox .vbox files, which are just big XML files storing all properties for a VM, we can grab the information we want from there.
This is the script that I use to list all forwarding rules. I can’t guarantee that it works with any version of VirtualBox, but it works with any version <=4.3 (the one I use).
Feel free to use the script, the worst that it can do is… not work 🙂
About things that weren't too obvious: you need to include the XML schema not only in the XPath of the XML node you're interested in, but in all definitions (!).
So, say you have a node with this path and these attributes (
xmlstarlet el -a lists all XPaths available in the XML file):
me@server:~ xmlstarlet el -a my_vm.vbox | grep Forwarding VirtualBox/Machine/Hardware/Network/Adapter/NAT/Forwarding VirtualBox/Machine/Hardware/Network/Adapter/NAT/Forwarding/@name VirtualBox/Machine/Hardware/Network/Adapter/NAT/Forwarding/@proto VirtualBox/Machine/Hardware/Network/Adapter/NAT/Forwarding/@hostport VirtualBox/Machine/Hardware/Network/Adapter/NAT/Forwarding/@guestport
To query those four attributes you need to specify the XML schema using the
-N option (easy to find in
xmlstarlet‘s docs), but you also need to set that schema for every single attribute name!
So, this will fail:
xmlstarlet sel -N x="http://www.innotek.de/VirtualBox-settings" -t \ -m "//x:Machine/Hardware/Network/Adapter/NAT/Forwarding" -v @name \ -o " " -v @hostport -o " " -v @guestport -n my_vm.vbox
but this will work (note the repeated
xmlstarlet sel -N x="http://www.innotek.de/VirtualBox-settings" -t \ -m "//x:Machine/x:Hardware/x:Network/x:Adapter/x:NAT/x:Forwarding" \ -v "concat(@name, ' - host:', @hostport, ' guest:', @guestport)" \ -n my_vm.vbox
I wish this was more explicit in