Fail if the size is too small for a bootstrap

Catch typos in the size option which would cause images which
are much too small for a bootstrap to be created.

Bug: #811464

2 files changed, 8 insertions, 4 deletions

diff --git a/bin/vmdebootstrap b/bin/vmdebootstrap
index b65a282..82dcfd7 100755
--- a/bin/vmdebootstrap
+++ b/bin/vmdebootstrap
@@ -147,6 +147,10 @@ class VmDebootstrap(cliapp.Application):  # pylint: disable=too-many-public-meth
             raise cliapp.AppException(
                 'You must give disk image filename or use either a '
                 'tarball filename or use squash')
+        if self.settings['size'] <= 100000000:
+            raise cliapp.AppException(
+                'A size of %s bytes is too small for a '
+                'bootstrap.' % self.settings['size'])
         if self.settings['image'] and not self.settings['size']:
             raise cliapp.AppException(
                 'If disk image is specified, you must give image size.')
diff --git a/yarns/200-fast-tests.yarn b/yarns/200-fast-tests.yarn
index 352c8ec..dc6ddf8 100644
--- a/yarns/200-fast-tests.yarn
+++ b/yarns/200-fast-tests.yarn
@@ -48,13 +48,13 @@ verify that vmdebootstrap parses the command line correctly.
     AND vmdebootstrap wrote an error message matching disk image filename
     AND vmdebootstrap wrote an error message matching squash
 
-    SCENARIO --image used with a zero size
+    SCENARIO --size too small for a bootstrap
     ASSUMING fast tests are requested
     WHEN user attempts to run vmdebootstrap
-    ... --image=FOO --size=0 --dry-run
+    ... --image=FOO --size=100M --dry-run
     THEN vmdebootstrap exited with a non-zero exit code
-    AND vmdebootstrap wrote an error message matching disk image
-    AND vmdebootstrap wrote an error message matching must
+    AND vmdebootstrap wrote an error message matching too small
+    AND vmdebootstrap wrote an error message matching bootstrap
 
     SCENARIO Debian distribution stable name check
     ASSUMING fast tests are requested