Create a missing partition table before creating a partition.

lib/linux_admin/disk.rb

@@ -88,7 +88,19 @@ def partitions
       end
     end
 
+    def create_partition_table(type = "msdos")
+      run!(cmd(:parted), :params => { nil => [path, "mklabel", type]})
+    end
+
+    def has_partition_table?
+      result = run(cmd(:parted), :params => { nil => [path, "print"]})
+
+      result_indicates_partition_table?(result)
+    end
+
     def create_partition(partition_type, size)
+      create_partition_table unless has_partition_table?
+
       id, start =
         partitions.empty? ? [1, 0] :
           [(partitions.last.id + 1),
@@ -118,5 +130,13 @@ def clear!
 
       self
     end
+
+    private
+
+    def result_indicates_partition_table?(result)
+      # parted exits with 1 but writes this oddly spelled error to stdout.
+      missing = (result.exit_status == 1 && result.output.include?("unrecognised disk label"))
+      !missing
+    end
   end
 end

spec/disk_spec.rb

@@ -106,6 +106,7 @@
       @disk.instance_variable_set(:@partitions,
                                   [LinuxAdmin::Partition.new(:id => 1,
                                                  :end_sector => 1024)])
+      @disk.stub(:has_partition_table? => true)
     end
 
     it "uses parted" do
@@ -139,6 +140,35 @@
         @disk.create_partition 'primary', 1024
       }.should change{@disk.partitions.size}.by(1)
     end
+
+    it "creates partition table if missing" do
+      @disk.stub(:has_partition_table? => false)
+      @disk.should_receive(:create_partition_table)
+      @disk.should_receive(:run!)
+      @disk.create_partition 'primary', 1024
+    end
+  end
+
+  describe "#has_partition_table?" do
+    it "positive case" do
+      disk = LinuxAdmin::Disk.new :path => '/dev/hda'
+      disk.should_receive(:run).and_return(double(:output => "", :exit_status => 0))
+      disk.should have_partition_table
+    end
+
+    it "negative case" do
+      disk = LinuxAdmin::Disk.new :path => '/dev/hda'
+      output = "\e[?1034h\r\rError: /dev/sdb: unrecognised disk label\n"
+      disk.should_receive(:run).and_return(double(:output => output, :exit_status => 1))
+      disk.should_not have_partition_table
+    end
+  end
+
+  it "#create_partition_table" do
+    disk = LinuxAdmin::Disk.new :path => '/dev/hda'
+    options = {:params => {nil => ["/dev/hda", "mklabel", "msdos"]}}
+    disk.should_receive(:run!).with(disk.cmd(:parted), options)
+    disk.create_partition_table
   end
 
   describe "#clear!" do