org.osbuild.grub2.inst

Install the grub2 boot loader for non-UEFI systems or hybrid boot

This stage can be used to generate a grub2 core image and install it to the correct location to enable booting of non-UEFI systems, i.e. x86 legacy and PPC64LE (Open Firmware). On x86, the core image can be installed into the MBR gap or to a dedicated BIOS boot partition when the partition label is GTP. On ppc64le with Open Firmware a dedicated 'PrEP partition' is used. x86 / MBR gap: For historic and performance reasons the first partition is aligned to a specific sector number (used to be 64, now it is 2048), which leaves a gap between it and the MBR, where the core image can be embedded in x86 / BIOS boot: A dedicated partition with a specific GUID[1] is used. ppc64le / Open Firmware: A dedicated partition with a specified GUID[2] is used. On ppc64le with Open Firmware a special partition called 'PrEP partition' is used the store the grub2 core; the firmware looks for this partition and directly loads and executes the core form it. On x86, a "boot image", aka grub stage 1, is installed into the master boot record (MBR) of the partition (even in the case the partition layout is GPT). It main purpose is to load the second stage (core image). Therefore the location of the core image is patched into the boot image. On ppc64le, the firmware itself directly loads the complete core image and transfers control to it. [1] 21686148-6449-6E6F-744E-656564454649 [2] 9E1A2D38-C612-4316-AA26-8B49521E5A8B

Schema 1

{
  "definitions": {
    "core-mkimage": {
      "type": "object",
      "description": "Generate the core image via grub-mkimage",
      "additionalProperties": false,
      "required": [
        "type",
        "partlabel",
        "filesystem"
      ],
      "properties": {
        "type": {
          "enum": [
            "mkimage"
          ]
        },
        "partlabel": {
          "type": "string",
          "enum": [
            "gpt",
            "dos"
          ]
        },
        "filesystem": {
          "type": "string",
          "enum": [
            "ext4",
            "xfs",
            "btrfs"
          ]
        },
        "binary": {
          "description": "grub-mkimage binary name",
          "type": "string",
          "default": "grub2-mkimage"
        }
      }
    },
    "prefix-partition": {
      "type": "object",
      "description": "Grub2 config on a specific partition, e.g. (,gpt3)/boot",
      "additionalProperties": false,
      "required": [
        "type",
        "partlabel",
        "number",
        "path"
      ],
      "properties": {
        "type": {
          "enum": [
            "partition"
          ]
        },
        "partlabel": {
          "type": "string",
          "enum": [
            "gpt",
            "dos"
          ]
        },
        "number": {
          "description": "The partition number, starting at zero",
          "type": "number"
        },
        "path": {
          "description": "location of grub config inside the partition",
          "type": "string",
          "pattern": "/.*"
        }
      }
    }
  },
  "additionalProperties": false,
  "required": [
    "filename",
    "platform",
    "location",
    "core",
    "prefix"
  ],
  "properties": {
    "filename": {
      "type": "string",
      "description": "filename of the disk image"
    },
    "platform": {
      "type": "string",
      "description": "Platform of the target system"
    },
    "location": {
      "type": "integer",
      "description": "Location of the stage 2 (in sectors)"
    },
    "core": {
      "description": "How to obtain the GRUB core image",
      "oneOf": [
        {
          "$ref": "#/definitions/core-mkimage"
        }
      ]
    },
    "prefix": {
      "description": "location of grub config",
      "oneOf": [
        {
          "$ref": "#/definitions/prefix-partition"
        }
      ]
    },
    "sector-size": {
      "type": "number",
      "description": "Sector size (in bytes)",
      "default": 512
    }
  }
}

Schema 2

{}