diff --git a/cmd/disk.go b/cmd/disk.go
new file mode 100644
index 0000000..5f21c79
--- /dev/null
+++ b/cmd/disk.go
@@ -0,0 +1,53 @@
+package cmd
+
+import (
+  "fmt"
+  "log"
+  "os"
+  "os/exec"
+
+  "github.com/spf13/cobra"
+)
+
+var (
+  size int
+  tempfile string
+)
+
+var diskCmd = &cobra.Command{
+  Use:   "disk",
+  Short: "Disk speed test.",
+  Long:  "Uses the local 'dd' command to test a disk's speed",
+  Run: func(cmd *cobra.Command, args []string) {
+    _, err := exec.LookPath("dd")
+  	if err != nil {
+  		panic(err)
+  	}
+
+    // get number of blocks to write (1M * 1024 * number of Gigabytes)
+    blocksCount := fmt.Sprintf("count=%d", (size * 1024))
+    // get outfile path
+    outfile := fmt.Sprintf("of=%s", tempfile)
+
+    ddCmd := exec.Command("dd", "bs=1M", blocksCount, "if=/dev/zero", outfile)
+    ddCmd.Stderr = os.Stdout
+    err = ddCmd.Run()
+    if err != nil {
+      log.Fatalf("cmd.Run() failed with %s\n", err)
+    }
+
+    fileErr := os.Remove(tempfile)
+    if fileErr != nil {
+      fmt.Println(fileErr)
+    }
+  },
+}
+
+func init() {
+  // link flags to variables
+  diskCmd.Flags().IntVarP(&size, "size", "s", 10, "Size of the file to write, in Gigabytes.")
+  diskCmd.Flags().StringVarP(&tempfile, "tempfile", "t", "./tempfile", "Where to store the tempfile.")
+
+  // add ping command to the main program
+  rootCmd.AddCommand(diskCmd)
+}
diff --git a/cmd/ping.go b/cmd/ping.go
index e75aca0..262ac88 100644
--- a/cmd/ping.go
+++ b/cmd/ping.go
@@ -38,6 +38,7 @@ var pingCmd = &cobra.Command{
 }
 
 func init() {
+  // link flags to variables
   pingCmd.Flags().StringVarP(&host, "host", "a", "8.8.8.8", "Host to attempt pinging.")
   pingCmd.Flags().IntVarP(&count, "count", "c", 50, "Number of pings to send.")