From f2530f19f66047cf073111f6f5d446940c2e4dc0 Mon Sep 17 00:00:00 2001
From: Lei Jitang <leijitang@huawei.com>
Date: Fri, 30 Sep 2016 05:27:07 -0400
Subject: [PATCH] Error out if rootfs type is not layers

The image spec requries that
````
MUST be set to layers. Implementations MUST generate an error if
they encounter a unknown value while verifying or unpacking an image.
```
The image-tool should act as the image spec says.

Signed-off-by: Lei Jiang <leijitang@huawei.com>
---
 image/config.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/image/config.go b/image/config.go
index 14e41e2..c6c7e86 100644
--- a/image/config.go
+++ b/image/config.go
@@ -53,6 +53,10 @@ func findConfig(w walker, d *descriptor) (*config, error) {
 		if err := json.Unmarshal(buf, &c); err != nil {
 			return err
 		}
+		// check if the rootfs type is 'layers'
+		if c.RootFS.Type != "layers" {
+			return fmt.Errorf("'%s' is an unknown rootfs type, MUST be 'layers'", c.RootFS.Type)
+		}
 		return errEOW
 	}); err {
 	case nil: