diff --git a/vagrantSandbox/README b/vagrantSandbox/README
index 367925f24..15631d112 100644
--- a/vagrantSandbox/README
+++ b/vagrantSandbox/README
@@ -32,6 +32,20 @@
   to the sources if you want to edit there directly. Use with care
   and don't compile in that directory unless you know what you're
   doing
+** Memory size and CPU-number
+   The number of CPUs in the virtual machine is determined by (the
+   first one that matches is used)
+   * If the variable =WM_VAGRANT_CPUS= exists then the number of CPUs
+     is set to this
+   * If the variable =WM_NCOMPPROCS= is set then the number of CPUs is
+     fixed with *half* that number (so that the virtual machine
+     doesn't make the machine unuable)
+   The amount of memory is set according to the number of CPUs:
+   $(1+N)*512$ Megabytes. This should allow half a Gigabyte for the OS
+   and half a Gigagbyte for each compiling process
+
+   The hostname of the virtual machine is the hostname of the host
+   machine prepended with =vagrant.=
 * Virtual machines
   Currently existing virtual machines are
   - precise :: Latest LTS Ubuntu. Currently the default machine to use
diff --git a/vagrantSandbox/Vagrantfile b/vagrantSandbox/Vagrantfile
index d3b3eedd4..65c0eecb6 100644
--- a/vagrantSandbox/Vagrantfile
+++ b/vagrantSandbox/Vagrantfile
@@ -4,12 +4,29 @@
 Vagrant.configure("2") do |config|
   config.vm.synced_folder "..", "/FOAM-sources"
 
+  config.vm.hostname="vagrant."+ENV["HOSTNAME"]
+
+  nrCPU=1
+  if ENV["WM_VAGRANT_CPUS"]
+    nrCPU=ENV["WM_VAGRANT_CPUS"].to_i
+  else
+    if ENV["WM_NCOMPPROCS"]
+      nrCPU=ENV["WM_NCOMPPROCS"].to_i/2
+    end
+  end
+  if nrCPU<1
+    nrCPU=1
+  end
+
   config.vm.provider :virtualbox do |vb|
     #   # Don't boot with headless mode
     #   vb.gui = true
     #
     #   # Use VBoxManage to customize the VM. For example to change memory:
-    vb.customize ["modifyvm", :id, "--memory", "1024"]
+    #     vb.customize ["modifyvm", :id, "--memory", "1024"]
+    vb.cpus=nrCPU
+    # make sure each CPU has enough memory
+    vb.memory=512*(1+nrCPU)
   end
 
   # default