grub2.inst: Add support for creating iso9660 boot image

Don't include the "location" offset, and use just a path for the prefix
section to set the path of the grub2 modules on the iso. eg.

{
    "filename": "eltorito.img",
    "platform": "i386-pc",
    "core": {
        "type": "mkimage",
        "partlabel": "gpt",
        "filesystem": "iso9660"
    },
    "prefix": {
        "path": "/boot/grub2/"
    }
}

stages/org.osbuild.grub2.inst

@@ -70,11 +70,11 @@ def write_core_image(core_f, image_f, location, sector_size):
     shutil.copyfileobj(core_f, image_f)
 
 
-def core_mkimage(platform: str, prefix: str, options: Dict,):
+def core_mkimage(platform: str, prefix: str, options: Dict):
     pt_label = options["partlabel"]
     fs_type = options["filesystem"]
 
-    os.makedirs("/var/tmp", exist_ok=True)
+    os.makedirs("/var/tmp/", exist_ok=True)
     core_path = "/var/tmp/grub2-core.img"
 
     # Create the level-2 & 3 stages of the bootloader, aka the core
@@ -88,8 +88,10 @@ def core_mkimage(platform: str, prefix: str, options: Dict,):
 
     if platform == "i386-pc":
         modules = ["biosdisk"]
+        gformat = "i386-pc"
     else:
         modules = []
+        gformat = "i386-pc"
 
     if pt_label in ["dos", "mbr"]:
         modules += ["part_msdos"]
@@ -102,6 +104,9 @@ def core_mkimage(platform: str, prefix: str, options: Dict,):
         modules += ["xfs"]
     elif fs_type == "btrfs":
         modules += ["btrfs"]
+    elif fs_type == "iso9660":
+        modules += ["iso9660"]
+        gformat = "i386-pc-eltorito"
     else:
         raise ValueError(f"unknown boot filesystem type: '{fs_type}'")
 
@@ -110,7 +115,7 @@ def core_mkimage(platform: str, prefix: str, options: Dict,):
                     "--verbose",
                     "--directory", f"/usr/lib/grub/{platform}",
                     "--prefix", prefix,
-                    "--format", platform,
+                    "--format", gformat,
                     "--compression", "auto",
                     "--output", core_path] +
                    modules,
@@ -133,18 +138,7 @@ def prefix_partition(options: Dict):
     return prefix
 
 
-def main(tree, options):
+def patch_core(location, core_path, image, sector_size, platform):
-    filename = options["filename"]
-    platform = options["platform"]
-    location = options["location"]
-    sector_size = options.get("sector-size", 512)
-
-    image = os.path.join(tree, filename.lstrip("/"))
-
-    prefix = prefix_partition(options["prefix"])
-    print(f"prefix: {prefix}")
-    core_path = core_mkimage(platform, prefix, options["core"])
-
     with open(image, "rb+") as image_f:
 
         # Write the newly created grub2 core to the image
@@ -168,6 +162,28 @@ def main(tree, options):
             with open(boot_path, "rb") as boot_f:
                 write_boot_image(boot_f, image_f, location)
 
+
+def main(tree, options):
+    filename = options["filename"]
+    platform = options["platform"]
+    sector_size = options.get("sector-size", 512)
+
+    image = os.path.join(tree, filename.lstrip("/"))
+
+    if "number" in options["prefix"]:
+        prefix = prefix_partition(options["prefix"])
+    else:
+        prefix = options["prefix"]["path"]
+    print(f"prefix: {prefix}")
+    core_path = core_mkimage(platform, prefix, options["core"])
+
+    location = options.get("location")
+    if location:
+        patch_core(location, core_path, image, sector_size, platform)
+    else:
+        # If location isn't set, use the image file as-is instead of with the MBR
+        shutil.copyfile(core_path, image)
+
     return 0
 
 

stages/org.osbuild.grub2.inst.meta.json

@@ -59,7 +59,8 @@
             "enum": [
               "ext4",
               "xfs",
-              "btrfs"
+              "btrfs",
+              "iso9660"
             ]
           },
           "binary": {
@@ -69,6 +70,21 @@
           }
         }
       },
+      "prefix-path": {
+        "type": "object",
+        "description": "Grub2 config path on iso9660 eg. /boot/grub2",
+        "additionalProperties": false,
+        "required": [
+          "path"
+        ],
+        "properties": {
+          "path": {
+            "description": "location of grub config inside the partition",
+            "type": "string",
+            "pattern": "/.*"
+          }
+        }
+      },
       "prefix-partition": {
         "type": "object",
         "description": "Grub2 config on a specific partition, e.g. (,gpt3)/boot",
@@ -108,7 +124,6 @@
     "required": [
       "filename",
       "platform",
-      "location",
       "core",
       "prefix"
     ],
@@ -138,6 +153,9 @@
         "oneOf": [
           {
             "$ref": "#/definitions/prefix-partition"
+          },
+          {
+            "$ref": "#/definitions/prefix-path"
           }
         ]
       },

stages/test/test_grub2_inst.py

@@ -31,3 +31,22 @@ def test_grub2_partition(tmp_path, stage_module):
     with open(treedir / "disk.img", "rb") as f:
         msg = f.read(12)
         assert msg != b"Just testing"
+
+def test_grub2_iso9660(tmp_path, stage_module):
+    treedir = tmp_path / "tree"
+    os.makedirs(treedir, exist_ok=True)
+
+    options = {
+        "filename": "eltorito.img",
+        "platform": "i386-pc",
+        "core": {
+            "type": "mkimage",
+            "partlabel": "gpt",
+            "filesystem": "iso9660",
+        },
+        "prefix": {
+            "path": "/boot/grub2/",
+        },
+    }
+    stage_module.main(treedir, options)
+    assert os.path.exists(treedir / "eltorito.img")