qemu-img fix

Author: Mehmet Aydoğdu

Gemfile.lock

@@ -0,0 +1,58 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    debug (1.9.2)
+      irb (~> 1.10)
+      reline (>= 0.3.8)
+    diff-lcs (1.5.1)
+    docile (1.4.1)
+    io-console (0.7.2)
+    irb (1.14.1)
+      rdoc (>= 4.0.0)
+      reline (>= 0.4.2)
+    psych (5.1.2)
+      stringio
+    rake (13.2.1)
+    rdoc (6.7.0)
+      psych (>= 4.0.0)
+    reline (0.5.10)
+      io-console (~> 0.5)
+    rspec (3.13.0)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.1)
+      rspec-support (~> 3.13.0)
+    rspec-debug (0.2.0)
+      debug (>= 1.3.3)
+    rspec-expectations (3.13.3)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.1)
+    simplecov (0.22.0)
+      docile (~> 1.1)
+      simplecov-html (~> 0.11)
+      simplecov_json_formatter (~> 0.1)
+    simplecov-html (0.13.1)
+    simplecov_json_formatter (0.1.4)
+    stringio (3.1.1)
+    systemu (2.6.5)
+    thor (1.3.2)
+
+PLATFORMS
+  ruby
+  x86_64-linux
+
+DEPENDENCIES
+  rake
+  rspec
+  rspec-debug
+  simplecov
+  systemu
+  thor
+
+BUNDLED WITH
+   2.5.16

README.md

@@ -342,6 +342,12 @@ NAME                                                      SIZE DAYS_AGO
   remote:ubuntu1404                                   270.4 Mb     88.1
 ```
 
+## Testing
+
+```
+sudo env PATH=$PATH rake
+```
+
 ## License
 
 Cangallo is licensed under the Apache License, Version 2.0.

lib/cangallo/qcow2.rb

@@ -160,10 +160,12 @@ def self.create_from_base(origin, destination, size=nil)
 
     def self.create(image, parent=nil, size=nil)
       cmd = [:create, '-f qcow2']
-      cmd << "-o backing_file=#{parent}" if parent
+      if parent
+        backing_fmt = File.extname(File.basename(parent)).delete_prefix('.')
+        cmd << "-o backing_file=#{parent},backing_fmt=#{backing_fmt}"
+      end
       cmd << image
       cmd << size if size
-
       execute(*cmd)
     end
   end