gistfile1.sh

#!/bin/bash

VM="$( basename "$0" )"

if [ -n "$1" ]; then
    # explicit control of the VM, e.g. `blah stop`
    # useful commands are 'pause', 'resume', 'stop', etc
    case "$1" in
        status) VBoxManage showvminfo "$VM" | grep -i state ;;
        *)      VBoxManage controlvm "$VM" ${1/stop/acpipowerbutton} ;; # much easier to type
    esac
else
    # otherwise just make sure it's up and provide a shell

    # boot the virtual machine in headless mode unless it's already running
    # note that there is a race condition if the machine is in the process of
    # powering down
    VBoxManage showvminfo --machinereadable "$VM" | grep -q 'VMState="running"' || \
    VBoxManage startvm "$VM" -type vrdp;

    # each VM has an SSH config like this:

    # Host $VM
    #     Hostname localhost
    #     Port 2222 # VBoxManage modifyvm "$VM" --natpf1 ...

    # changing ssh port forwarding doesn't require restarting the VM (whereas
    # fiddling with VirtualBox port forwarding does). The following section
    # should probably just be a per VM include, but for my needs it does the
    # job as is.

    # ControlMaster works nicely with a global 'ControlPath /tmp/%r@%h:%p' in
    # my ~/.ssh/config this means the port forwarding stays up no matter how
    # many shells I open and close (unlike ControlMaster auto in the config)

    # this loop quietly waits till sshd is up
    until nc -z localhost 3000 >/dev/null; do
        echo -n "."
        ssh -N -f -q \
            -L 3000:localhost:3000 \
            -o ConnectTimeout=1 \
            -o ControlMaster=yes \
            "$VM" && echo;
    done

    # finally, start a shell
    exec ssh "$VM"
fi