diff -r 9f08c4e82037 tools/examples/xend-config.sxp
--- a/tools/examples/xend-config.sxp	Mon Jul 12 18:39:18 2010 +0100
+++ b/tools/examples/xend-config.sxp	Mon Jul 12 22:05:56 2010 +0200
@@ -205,6 +205,11 @@
 # enable-dom0-ballooning below) and for xm mem-set when applied to dom0.
 (dom0-min-mem 196)
 
+# Dom0 will need at least specified amount of free space for
+# /var/lib/xen otherwise it will refuse to start up any new
+# guests. Value is in MB and setting it to 0 disables the check.
+(dom0-min-space 0)
+
 # Whether to enable auto-ballooning of dom0 to allow domUs to be created.
 # If enable-dom0-ballooning = no, dom0 will never balloon out.
 (enable-dom0-ballooning yes)
diff -r 9f08c4e82037 tools/python/xen/xend/XendDomainInfo.py
--- a/tools/python/xen/xend/XendDomainInfo.py	Mon Jul 12 18:39:18 2010 +0100
+++ b/tools/python/xen/xend/XendDomainInfo.py	Mon Jul 12 22:05:56 2010 +0200
@@ -2837,6 +2837,16 @@
 
         self._configureBootloader()
 
+        # Check whether dom0 does have enough free space to create the guest
+        stat = os.statvfs("/var/lib/xen")
+        free = int((stat.f_bsize * stat.f_bavail) / 1048576)
+        log.debug("Free space for Xen files on dom0: %s MiB" % free)
+        dom0_min_space = xoptions.instance().get_dom0_min_space()
+        if dom0_min_space > 0 and free < dom0_min_space:
+            raise XendError('Dom0 requires at least %s MiBs free space for '
+                            '/var/lib/xen but only %s MiBs is available.' %
+                            (dom0_min_space, free))
+
         try:
             self.image = image.create(self, self.info)
 
diff -r 9f08c4e82037 tools/python/xen/xend/XendOptions.py
--- a/tools/python/xen/xend/XendOptions.py	Mon Jul 12 18:39:18 2010 +0100
+++ b/tools/python/xen/xend/XendOptions.py	Mon Jul 12 22:05:56 2010 +0200
@@ -105,6 +105,8 @@
 
     dom0_min_mem_default = 0
 
+    dom0_min_space_default = 0
+
     reserved_memory_default = 0
 
     dom0_vcpus_default = 0
@@ -359,6 +361,9 @@
     def get_dom0_min_mem(self):
         return self.get_config_int('dom0-min-mem', self.dom0_min_mem_default)
 
+    def get_dom0_min_space(self):
+        return self.get_config_int('dom0-min-space', self.dom0_min_space_default)
+
     def get_enable_dom0_ballooning(self):
         enable_dom0_ballooning_default = 'yes'
         if self.get_dom0_min_mem() == 0: